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1.  Trends in Parent-Child Correlations of Childhood Body Mass Index during the Development of the Obesity Epidemic 
PLoS ONE  2014;9(10):e109932.
The intergenerational resemblance in body mass index may have increased during the development of the obesity epidemic due to changes in environment and/or expression of genetic predisposition.
This study investigates trends in intergenerational correlations of childhood body mass index (BMI; kg/m2) during the emergence of the obesity epidemic.
The study population was derived from the Copenhagen School Health Records Register, which includes height and weight measurements since birth year 1930. Mothers and fathers with BMIs available at ages 7 (n = 25,923 and n = 20,972) or 13 years (n = 26,750 and n = 21,397), respectively, were linked through the civil registration system introduced in 1968 to their children with BMIs available at age 7 years. Age- and sex-specific BMI z-scores were calculated. Correlations were estimated across eight intervals of child birth years (1952–1989) separately by sex. Trends in these correlations were examined. Whereas the mother-child correlations reflected the biological relationship, a likely decline in the assignment of non-biological fathers through the registration system across time must be considered when interpreting the father-child correlations.
The BMI correlations between mothers and sons ranged from 0.29–0.36 and they decreased marginally, albeit significantly across time at ages 7–7 years (−0.002/year, p = 0.006), whereas those at 13–7 years remained stable (<0.0004/year, p = 0.96). Mother-daughter correlations ranged from 0.30–0.34, and they were stable at ages 7–7 years (0.0001/year, p = 0.84) and at 13–7 years (0.0004/year, p = 0.56). In contrast, father-son correlations increased significantly during this period, both at ages 7–7 (0.002/year, p = 0.007) and at ages 13–7 years (0.003/year, p<0.001), whereas the increase in father-daughter correlations were insignificant both at ages 7–7 (0.001/year, p = 0.37) and at ages 13–7 years (0.001/year, p = 0.18).
During the obesity epidemics development, the intergenerational resemblance with mothers remained stable, whereas the father-child BMI resemblance increased, possibly reflecting changes in family relationships, and unlikely to have influenced the epidemic.
PMCID: PMC4201474  PMID: 25329656
3.  The Validation and Assessment of Machine Learning: A Game of Prediction from High-Dimensional Data 
PLoS ONE  2009;4(8):e6287.
In applied statistics, tools from machine learning are popular for analyzing complex and high-dimensional data. However, few theoretical results are available that could guide to the appropriate machine learning tool in a new application. Initial development of an overall strategy thus often implies that multiple methods are tested and compared on the same set of data. This is particularly difficult in situations that are prone to over-fitting where the number of subjects is low compared to the number of potential predictors. The article presents a game which provides some grounds for conducting a fair model comparison. Each player selects a modeling strategy for predicting individual response from potential predictors. A strictly proper scoring rule, bootstrap cross-validation, and a set of rules are used to make the results obtained with different strategies comparable. To illustrate the ideas, the game is applied to data from the Nugenob Study where the aim is to predict the fat oxidation capacity based on conventional factors and high-dimensional metabolomics data. Three players have chosen to use support vector machines, LASSO, and random forests, respectively.
PMCID: PMC2716515  PMID: 19652722
5.  Fibronectin as predictor of cirrhosis in men who abuse alcohol 
In a study of 142 male alcohol abusers without evidence of cirrhosis the presence of intralobular fibronectin in the liver was investigated in relation to the subsequent development of the disease. All 142 initial biopsy samples showed preserved architecture. During a follow up period of 10-13 years 23 patients (16%) developed cirrhosis. Twelve of 110 patients with normal or slightly increased amounts of parenchymal fibronectin in the initial biopsy specimen developed cirrhosis, whereas eight out of 27 patients with moderately increased amounts and three out of five with significantly increased amounts later developed the disease (p<0·005).
Semiquantitative assessment of the amount of parenchymal fibronectin at an early stage of alcoholic liver disease is of definite predictive value for the development of cirrhosis.
PMCID: PMC2546159  PMID: 3135046
6.  A Genome-Wide Association Study of Monozygotic Twin-Pairs Suggests a Locus Related to Variability of Serum High-Density Lipoprotein Cholesterol 
Genome-wide association analysis on monozygotic twin pairs offers a route to discovery of gene–environment interactions through testing for variability loci associated with sensitivity to individual environment/lifestyle. We present a genome-wide scan of loci associated with intra-pair differences in serum lipid and apolipoprotein levels. We report data for 1,720 monozygotic female twin pairs from GenomEUtwin project with 2.5 million SNPs, imputed or genotyped, and measured serum lipid fractions for both twins. We found one locus associated with intra-pair differences in high density lipoprotein (HDL) cholesterol, rs2483058 in an intron of SRGAP2, where twins carrying the C allele are more sensitive to environmental factors (p = 3.98 × 10−8). We followed up the association in further genotyped monozygotic twins (N = 1 261) which showed a moderate association for the variant (p = .002, same direction of an effect). In addition, we report a new association on the level of apolipoprotein A-II (p = 4.03 × 10−8).
PMCID: PMC4333218  PMID: 23031429
twins; association; lipids; apolipoproteins; interaction
7.  Novel variation and de novo mutation rates in population-wide de novo assembled Danish trios 
Nature Communications  2015;6:5969.
Building a population-specific catalogue of single nucleotide variants (SNVs), indels and structural variants (SVs) with frequencies, termed a national pan-genome, is critical for further advancing clinical and public health genetics in large cohorts. Here we report a Danish pan-genome obtained from sequencing 10 trios to high depth (50 × ). We report 536k novel SNVs and 283k novel short indels from mapping approaches and develop a population-wide de novo assembly approach to identify 132k novel indels larger than 10 nucleotides with low false discovery rates. We identify a higher proportion of indels and SVs than previous efforts showing the merits of high coverage and de novo assembly approaches. In addition, we use trio information to identify de novo mutations and use a probabilistic method to provide direct estimates of 1.27e−8 and 1.5e−9 per nucleotide per generation for SNVs and indels, respectively.
The generation of a national pan-genome, a population-specific catalogue of genetic variation, may advance the impact of clinical genetics studies. Here the Besenbacher et al. carry out deep sequencing and de novo assembly of 10 parent–child trios to generate a Danish pan-genome that provides insight into structural variation, de novo mutation rates and variant calling.
PMCID: PMC4309431  PMID: 25597990
8.  Childhood height and body mass index were associated with risk of adult thyroid cancer in a large cohort study 
Cancer research  2013;74(1):235-242.
Taller stature and obesity in adulthood have been consistently associated with an increased risk of thyroid cancer, but few studies have investigated the role of childhood body size. Using data from a large prospective cohort, we examined associations for height and body mass index (BMI) at ages 7–13 with risk of thyroid cancer in later life. The study population included 321,085 children from the Copenhagen School Health Records Register, born between 1930 and 1989 in Copenhagen, Denmark, with measurements of height and weight from 7–13 years of age. These data were linked with the Danish Cancer Registry to identify incident thyroid cancer cases (1968–2010). Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated for age-and sex-specific height and BMI standard deviation scores (SDSs) using proportional hazards models stratified by birth cohort and sex. During follow-up (median=38.6 years), 171 women and 64 men were diagnosed with thyroid cancer. Both height and BMI were positively associated with thyroid cancer risk, and these associations were similar by age at measurement. Using age 10 as an example, HRs per 1-unit increase in SDS for height (approximately 6–7 cm) and BMI (approximately 1.5–2 kg/m2) were 1.22 (95% CI: 1.07–1.40) and 1.15 (95% CI: 1.00–1.34), respectively. These results, together with the relatively young ages at which thyroid cancers are diagnosed compared with other malignancies, suggest a potential link between early-life factors related to growth and body weight and thyroid carcinogenesis.
PMCID: PMC3891884  PMID: 24247722
prospective study; obesity; body mass index; height; childhood; adolescence; thyroid neoplasms
9.  Stratification by Smoking Status Reveals an Association of CHRNA5-A3-B4 Genotype with Body Mass Index in Never Smokers 
PLoS Genetics  2014;10(12):e1004799.
We previously used a single nucleotide polymorphism (SNP) in the CHRNA5-A3-B4 gene cluster associated with heaviness of smoking within smokers to confirm the causal effect of smoking in reducing body mass index (BMI) in a Mendelian randomisation analysis. While seeking to extend these findings in a larger sample we found that this SNP is associated with 0.74% lower body mass index (BMI) per minor allele in current smokers (95% CI -0.97 to -0.51, P = 2.00×10−10), but also unexpectedly found that it was associated with 0.35% higher BMI in never smokers (95% CI +0.18 to +0.52, P = 6.38×10−5). An interaction test confirmed that these estimates differed from each other (P = 4.95×10−13). This difference in effects suggests the variant influences BMI both via pathways unrelated to smoking, and via the weight-reducing effects of smoking. It would therefore be essentially undetectable in an unstratified genome-wide association study of BMI, given the opposite association with BMI in never and current smokers. This demonstrates that novel associations may be obscured by hidden population sub-structure. Stratification on well-characterized environmental factors known to impact on health outcomes may therefore reveal novel genetic associations.
Author Summary
We found that a single nucleotide polymorphism in the CHRNA5-A3-B4 gene cluster, which is known to influence smoking heaviness, is associated with lower body mass index (BMI) in current smokers, but higher BMI in never smokers. This difference in effects suggests that the variant influences BMI both via pathways other than smoking, and via the weight-reducing effects of smoking, in opposite directions. The overall effect on BMI would therefore be undetectable in an unstratified genome-wide association study, indicating that novel associations may be obscured by hidden population sub-structure.
PMCID: PMC4256159  PMID: 25474695
10.  Childhood height and birth weight in relation to future prostate cancer risk: a cohort study based on the Copenhagen School Health Records Register 
Adult height has been positively associated with prostate cancer risk. However, the exposure window of importance is currently unknown and assessments of height during earlier growth periods are scarce. In addition, the association between birth weight and prostate cancer remains undetermined. We assessed these relationships a cohort of the Copenhagen School Health Records Register (CSHRR).
The CSHRR comprises 372,636 school children. For boys born between the 1930’s and 1969, birth weight and annual childhood heights—measured between ages 7 and 13 years—were analyzed in relation to prostate cancer risk. Cox proportional hazards regression models were used to estimate hazard ratios (HR) and 95 percent confidence intervals (95%CI).
There were 125,211 males for analysis, 2,987 of who were subsequently diagnosed with prostate cancer during 2.57 million person-years of follow-up. Height z-score was significantly associated with prostate cancer risk at all ages (HR~1.13). Height at age 13 years was more important than height change (p=0.024) and height at age 7 years (p=0.024), when estimates from mutually adjusted models were compared. Adjustment of birth weight did not alter estimates ascertained. Birth weight was not associated with prostate cancer risk.
The association between childhood height and prostate cancer risk was driven by height at age 13 years.
Our findings implicate late childhood, adolescence and adulthood growth periods as containing the exposure window(s) of interest that underlies the association between height and prostate cancer. The causal factor may not be singular given the complexity of both human growth and carcinogenesis.
PMCID: PMC3863763  PMID: 24089459
prostate neoplasms; body height; growth; body weights and measures; birth weight; cohort studies
11.  Interaction between Genetic Predisposition to Adiposity and Dietary Protein in Relation to Subsequent Change in Body Weight and Waist Circumference 
PLoS ONE  2014;9(10):e110890.
Genetic predisposition to adiposity may interact with dietary protein in relation to changes of anthropometry.
To investigate the interaction between genetic predisposition to higher body mass index (BMI), waist circumference (WC) or waist-hip ratio adjusted for BMI (WHRBMI) and dietary protein in relation to subsequent change in body weight (ΔBW) or change in WC (ΔWC).
Three different Danish cohorts were used. In total 7,054 individuals constituted the study population with information on diet, 50 single-nucleotide polymorphisms (SNPs) associated with BMI, WC or WHRBMI, as well as potential confounders. Mean follow-up time was ∼5 years. Four genetic predisposition-scores were based on the SNPs; a complete-score including all selected adiposity- associated SNPs, and three scores including BMI, WC or WHRBMI associated polymorphisms, respectively. The association between protein intake and ΔBW or ΔWC were examined and interactions between SNP-score and protein were investigated. Analyses were based on linear regressions using macronutrient substitution models and meta-analyses.
When protein replaced carbohydrate, meta-analyses showed no associations with ΔBW (41.0 gram/y/5 energy% protein, [95% CI: −32.3; 114.3]) or ΔWC (<−0.1 mm/y/5 energy % protein, [−1.1; 1.1]). Similarly, there were no interactions for any SNP-scores and protein for either ΔBW (complete SNP-score: 1.8 gram/y/5 energy% protein/risk allele, [−7.0; 10.6]) or ΔWC (complete SNP-score: <0.1 mm/y/5 energy% protein/risk allele, [−0.1; 0.1]). Similar results were seen when protein replaced fat.
This study indicates that the genetic predisposition to general and abdominal adiposity, assessed by gene-scores, does not seem to modulate the influence of dietary protein on ΔBW or ΔWC.
PMCID: PMC4211714  PMID: 25350854
12.  Risk of Childhood Overweight after Exposure to Tobacco Smoking in Prenatal and Early Postnatal Life 
PLoS ONE  2014;9(10):e109184.
To investigate the association between exposure to mothers smoking during prenatal and early postnatal life and risk of overweight at age 7 years, while taking birth weight into account.
From the Danish National Birth Cohort a total of 32,747 families were identified with available information on maternal smoking status in child's pre- and postnatal life and child's birth weight, and weight and height at age 7 years. Outcome was overweight according to the International Obesity Task Force gender and age specific body mass index. Smoking exposure was categorized into four groups: no exposure (n = 25,076); exposure only during pregnancy (n = 3,343); exposure only postnatally (n = 140); and exposure during pregnancy and postnatally (n = 4,188). Risk of overweight according to smoking status as well as dose-response relationships were estimated by crude and adjusted odds ratios using logistic regression models.
Exposure to smoking only during pregnancy, or both during pregnancy and postnatally were both significantly associated with overweight at 7 years of age (OR: 1.31, 95% CI: 1.15–1.48, and OR: 1.76, 95% CI: 1.58–1.97, respectively). Analyses excluding children with low birth weight (<2,500 gram) revealed similar results. A significant prenatal dose-response relationship was found. Per one additional cigarette smoked per day an increase in risk of overweight was observed (OR: 1.02, 95% CI: 1.01–1.03). When adjusting for quantity of smoking during pregnancy, prolonged exposure after birth further increased the risk of later overweight in the children (OR 1.28, 95% CI:1.09–1.50) compared with exposure only in the prenatal period.
Mother's perinatal smoking increased child's OR of overweight at age 7 years irrespective of birth weight, and with higher OR if exposed both during pregnancy and in early postnatal life. Clear dose-response relationships were observed, which emphasizes the need for prevention of any tobacco exposure of infants.
PMCID: PMC4195647  PMID: 25310824
13.  Body Characteristics, Dietary Protein and Body Weight Regulation. Reconciling Conflicting Results from Intervention and Observational Studies? 
PLoS ONE  2014;9(7):e101134.
Physiological evidence indicates that high-protein diets reduce caloric intake and increase thermogenic response, which may prevent weight gain and regain after weight loss. Clinical trials have shown such effects, whereas observational cohort studies suggest an association between greater protein intake and weight gain. In both types of studies the results are based on average weight changes, and show considerable diversity in both directions. This study investigates whether the discrepancy in the evidence could be due to recruitment of overweight and obese individuals into clinical trials.
Data were available from the European Diet, Obesity and Genes (DiOGenes) post-weight-loss weight-maintenance trial and the Danish Diet, Cancer and Health (DCH) cohort. Participants of the DCH cohort were matched with participants from the DiOGenes trial on gender, diet, and body characteristics. Different subsets of the DCH-participants, comparable with the trial participants, were analyzed for weight maintenance according to the randomization status (high or low protein) of the matched trial participants.
Trial participants were generally heavier, had larger waist circumference and larger fat mass than the participants in the entire DCH cohort. A better weight maintenance in the high-protein group compared to the low protein group was observed in the subgroups of the DCH cohort matching body characteristics of the trial participants.
This modified observational study, minimized the differences between the RCT and observational data with regard to dietary intake, participant characteristics and statistical analysis. Compared with low protein diet the high protein diet was associated with better weight maintenance when individuals with greater body mass index and waist circumference were analyzed. Selecting subsets of large-scale observational cohort studies with similar characteristics as participants in clinical trials may reconcile the otherwise conflicting results.
PMCID: PMC4081118  PMID: 24992329
14.  Genome-wide association and longitudinal analyses reveal genetic loci linking pubertal height growth, pubertal timing and childhood adiposity 
Human Molecular Genetics  2013;22(13):2735-2747.
The pubertal height growth spurt is a distinctive feature of childhood growth reflecting both the central onset of puberty and local growth factors. Although little is known about the underlying genetics, growth variability during puberty correlates with adult risks for hormone-dependent cancer and adverse cardiometabolic health. The only gene so far associated with pubertal height growth, LIN28B, pleiotropically influences childhood growth, puberty and cancer progression, pointing to shared underlying mechanisms. To discover genetic loci influencing pubertal height and growth and to place them in context of overall growth and maturation, we performed genome-wide association meta-analyses in 18 737 European samples utilizing longitudinally collected height measurements. We found significant associations (P < 1.67 × 10−8) at 10 loci, including LIN28B. Five loci associated with pubertal timing, all impacting multiple aspects of growth. In particular, a novel variant correlated with expression of MAPK3, and associated both with increased prepubertal growth and earlier menarche. Another variant near ADCY3-POMC associated with increased body mass index, reduced pubertal growth and earlier puberty. Whereas epidemiological correlations suggest that early puberty marks a pathway from rapid prepubertal growth to reduced final height and adult obesity, our study shows that individual loci associating with pubertal growth have variable longitudinal growth patterns that may differ from epidemiological observations. Overall, this study uncovers part of the complex genetic architecture linking pubertal height growth, the timing of puberty and childhood obesity and provides new information to pinpoint processes linking these traits.
PMCID: PMC3674797  PMID: 23449627
15.  Severe Maternal Stress Exposure Due to Bereavement before, during and after Pregnancy and Risk of Overweight and Obesity in Young Adult Men: A Danish National Cohort Study 
PLoS ONE  2014;9(5):e97490.
Perinatal stress may programme overweight and obesity. We examined whether maternal pre- and post-natal bereavement was associated with overweight and obesity in young men.
A cohort study was conducted including 119,908 men born from 1976 to 1993 and examined for military service between 2006 and 2011. Among them, 4,813 conscripts were born to mothers bereaved by death of a close relative from 12 months preconception to birth of the child (exposed group). Median body mass index (BMI) and prevalence of overweight and obesity were estimated. Odds ratio of overweight (BMI≥25 kg/m2) and obesity (BMI≥30 kg/m2) were estimated by logistic regression analysis adjusted for maternal educational level.
Median BMI was similar in the exposed and the unexposed group but the prevalence of overweight (33.3% versus 30.4%, p = 0.02) and obesity (9.8% versus 8.5%, p = 0.06) was higher in the exposed group. Conscripts exposed 6 to 0 months before conception and during pregnancy had a higher risk of overweight (odds ratio 1.15, 95% confidence interval (CI): 1.03; 1.27 and odds ratio 1.13, 95% CI: 1.03; 1.25, respectively). Conscripts born to mothers who experienced death of the child’s biological father before child birth had a two-fold risk of obesity (odds ratio 2.00, 95% CI: 0.93; 4.31). There was no elevated risk in those who experienced maternal bereavement postnatally.
Maternal bereavement during the prenatal period was associated with increased risk of overweight or obesity in a group of young male conscripts, and this may possibly be reflected to severe stress exposure early in life. However, not all associations were clear, and further studies are warranted.
PMCID: PMC4020839  PMID: 24828434
16.  Stability of the Associations between Early Life Risk Indicators and Adolescent Overweight over the Evolving Obesity Epidemic 
PLoS ONE  2014;9(4):e95314.
Pre- and perinatal factors and preschool body size may help identify children developing overweight, but these factors might have changed during the development of the obesity epidemic.
We aimed to assess the associations between early life risk indicators and overweight at the age of 9 and 15 years at different stages of the obesity epidemic.
We used two population-based Northern Finland Birth Cohorts including 4111 children born in 1966 (NFBC1966) and 5414 children born in 1985–1986 (NFBC1986). In both cohorts, we used the same a priori defined prenatal factors, maternal body mass index (BMI), birth weight, infant weight (age 5 months and 1 year), and preschool BMI (age 2–5 years). We used internal references in early childhood to define percentiles of body size (<50, 50–75, 75–90 and >90) and generalized linear models to study the association with overweight, according to the International Obesity Taskforce (IOTF) definitions, at the ages of 9 and 15 years.
The prevalence of overweight at the age of 15 was 9% for children born in 1966 and 16% for children born in 1986. However, medians of infant weight and preschool BMI changed little between the cohorts, and we found similar associations between maternal BMI, infant weight, preschool BMI, and later overweight in the two cohorts. At 5 years, children above the 90th percentile had approximately a 12 times higher risk of being overweight at the age of 15 years compared to children below the 50th percentile in both cohorts.
The associations between early body size and adolescent overweight showed remarkable stability, despite the increase in prevalence of overweight over the 20 years between the cohorts. Using consequently defined internal percentiles may be a valuable tool in clinical practice.
PMCID: PMC3991687  PMID: 24748033
17.  Do rapid BMI growth in childhood and early-onset obesity offer cardiometabolic protection to obese adults in mid-life? Analysis of a longitudinal cohort study of Danish men 
BMJ Open  2014;4(4):e004827.
Some obese individuals have no cardiometabolic abnormalities; they are ‘metabolically healthy, but obese’ (MHO). Similarly, some non-obese individuals have cardiometabolic abnormalities, that is, ‘metabolically at risk, normal weight’ (MANW). Previous studies have suggested that early-onset obesity may be associated with MHO. We aimed to assess whether body mass index (BMI) in childhood and early-onset obesity are associated with MHO.
General population longitudinal cohort study, Denmark.
From 362 200 young men (mean age 20) examined for Danish national service between 1943 and 1977, all obese men (BMI ≥31 kg/m2, N=1930) were identified along with a random 1% sample of the others (N=3601). Our analysis includes 2392 of these men attending a research clinic in mid-life (mean age 42). For 613 of these men, data on childhood BMI are available. We summarised childhood BMI growth (7–13 years) using a multilevel model. Early-onset obesity was defined as obesity at examination for national service.
Outcome measurement
We defined metabolic health at the mid-life clinic as non-fasting serum cholesterol <6.6 mmol/L, non-fasting glucose <8.39 mmol/L and pulse pressure <48 mm Hg. Participants were categorised into four groups according to their obesity (BMI ≥30 kg/m2) and metabolic health in mid-life.
297 of 1097 (27.1%) of obese men were metabolically healthy; 826 of 1295 (63.8%) non-obese men had at least one metabolic abnormality. There was no evidence that rapid BMI growth in childhood or early-onset obesity was associated with either MHO or the MANW phenotype, for example, among obese men in mid-life, the OR for MHO comparing early-onset obesity with non-early-onset obesity was 0.97 (95% CI 0.85 to 1.10).
We found no robust evidence that early-onset obesity or rapid BMI growth in childhood is protective for cardiometabolic health.
PMCID: PMC3996819  PMID: 24736038
18.  Maternal Pre-Pregnancy BMI and Intelligence Quotient (IQ) in 5-Year-Old Children: A Cohort Based Study 
PLoS ONE  2014;9(4):e94498.
An association between maternal pre-pregnancy BMI and childhood intelligence quotient (IQ) has repeatedly been found but it is unknown if this association is causal or due to confounding caused by genetic or social factors.
We used a cohort of 1,783 mothers and their 5-year-old children sampled from the Danish National Birth Cohort. The children participated between 2003 and 2008 in a neuropsychological assessment of cognitive ability including IQ tests taken by both the mother and the child. Linear regression analyses were used to estimate the associations between parental BMI and child IQ adjusted for a comprehensive set of potential confounders. Child IQ was assessed with the Wechsler Primary and Preschool Scales of Intelligence – Revised (WPPSI-R).
The crude association between maternal BMI and child IQ showed that BMI was adversely associated with child IQ with a reduction in IQ of −0.40 point for each one unit increase in BMI. This association was attenuated after adjustment for social factors and maternal IQ to a value of −0.27 (−0.50 to −0.03). After mutual adjustment for the father's BMI and all other factors except maternal IQ, the association between paternal BMI and child IQ yielded a regression coefficient of −0.26 (−0.59 to 0.07), which was comparable to that seen for maternal BMI (−0.20 (−0.44 to 0.04)).
Although maternal pre-pregnancy BMI was inversely associated with the IQ of her child, the similar association with paternal BMI suggests that it is not a specific pregnancy related adiposity effect.
PMCID: PMC3984139  PMID: 24727836
19.  Genome-wide linkage analysis for human longevity: Genetics of Healthy Ageing Study 
Aging cell  2013;12(2):184-193.
Clear evidence exists for heritability of human longevity, and much interest is focused on identifying genes associated with longer lives. To identify such longevity alleles, we performed the largest genome-wide linkage scan thus far reported. Linkage analyses included 2118 nonagenarian Caucasian sibling pairs that have been enrolled in fifteen study centers of eleven European countries as part of the Genetics of Healthy Ageing (GEHA) project. In the joint linkage analyses we observed four regions that show linkage with longevity; chromosome 14q11.2 (LOD=3.47), chromosome 17q12-q22 (LOD=2.95), chromosome 19p13.3-p13.11 (LOD=3.76) and chromosome 19q13.11-q13.32 (LOD=3.57). To fine map these regions linked to longevity, we performed association analysis using GWAS data in a subgroup of 1,228 unrelated nonagenarian and 1,907 geographically matched controls. Using a fixed effect meta-analysis approach, rs4420638 at the TOMM40/APOE/APOC1 gene locus showed significant association with longevity (p-value=9.6 × 10−8). By combined modeling of linkage and association we showed that association of longevity with APOEε4 and APOEε2 alleles explain the linkage at 19q13.11-q13.32 with p-value=0.02 and p-value=1.0 × 10−5, respectively. In the largest linkage scan thus far performed for human familial longevity, we confirm that the APOE locus is a longevity gene and that additional longevity loci may be identified at 14q11.2, 17q12-q22 and 19p13.3-p13.11. Since the latter linkage results are not explained by common variants, we suggest that rare variants play an important role in human familial longevity.
PMCID: PMC3725963  PMID: 23286790
Human familial longevity; genome-wide linkage analysis; APOE gene; association analysis; nonagenarian sibling pairs
20.  Chronic Family Stress Moderates the Association between a TOMM40 Variant and Triglyceride Levels in Two Independent Caucasian Samples 
Biological psychology  2013;93(1):184-189.
TOMM40 SNP rs157580 has been associated with triglyceride levels in Genome-wide association studies (GWAS). Chronic caregiving stress moderates the association between triglyceride levels and a nearby SNP rs439401 that is associated with triglyceride levels in GWAS. Here, we report data from two independent Caucasian samples (242 U.S. women and men; 466 Danish men) testing the hypothesis that chronic family stress also moderates the association between rs157580 and triglyceride levels. The interaction of rs157580 and family stress in predicting triglyceride levels was statistically significant in the U.S. sample (p = 0.004) and marginally significant (p = 0.075) in the Danish sample. The G allele of rs157580 was associated with increased triglyceride levels among family stressed cases in both samples compared with A/A cases, but not among controls. Chronic family stress moderates the association of rs157580 variants with triglyceride levels and should be taken into account for disease risk assessment and potential intervention.
PMCID: PMC3739426  PMID: 23435269
21.  Genome-wide association meta-analysis of human longevity identifies a novel locus conferring survival beyond 90 years of age 
Deelen, Joris | Beekman, Marian | Uh, Hae-Won | Broer, Linda | Ayers, Kristin L. | Tan, Qihua | Kamatani, Yoichiro | Bennet, Anna M. | Tamm, Riin | Trompet, Stella | Guðbjartsson, Daníel F. | Flachsbart, Friederike | Rose, Giuseppina | Viktorin, Alexander | Fischer, Krista | Nygaard, Marianne | Cordell, Heather J. | Crocco, Paolina | van den Akker, Erik B. | Böhringer, Stefan | Helmer, Quinta | Nelson, Christopher P. | Saunders, Gary I. | Alver, Maris | Andersen-Ranberg, Karen | Breen, Marie E. | van der Breggen, Ruud | Caliebe, Amke | Capri, Miriam | Cevenini, Elisa | Collerton, Joanna C. | Dato, Serena | Davies, Karen | Ford, Ian | Gampe, Jutta | Garagnani, Paolo | de Geus, Eco J.C. | Harrow, Jennifer | van Heemst, Diana | Heijmans, Bastiaan T. | Heinsen, Femke-Anouska | Hottenga, Jouke-Jan | Hofman, Albert | Jeune, Bernard | Jonsson, Palmi V. | Lathrop, Mark | Lechner, Doris | Martin-Ruiz, Carmen | Mcnerlan, Susan E. | Mihailov, Evelin | Montesanto, Alberto | Mooijaart, Simon P. | Murphy, Anne | Nohr, Ellen A. | Paternoster, Lavinia | Postmus, Iris | Rivadeneira, Fernando | Ross, Owen A. | Salvioli, Stefano | Sattar, Naveed | Schreiber, Stefan | Stefánsson, Hreinn | Stott, David J. | Tiemeier, Henning | Uitterlinden, André G. | Westendorp, Rudi G.J. | Willemsen, Gonneke | Samani, Nilesh J. | Galan, Pilar | Sørensen, Thorkild I.A. | Boomsma, Dorret I. | Jukema, J. Wouter | Rea, Irene Maeve | Passarino, Giuseppe | de Craen, Anton J.M. | Christensen, Kaare | Nebel, Almut | Stefánsson, Kári | Metspalu, Andres | Magnusson, Patrik | Blanché, Hélène | Christiansen, Lene | Kirkwood, Thomas B.L. | van Duijn, Cornelia M. | Franceschi, Claudio | Houwing-Duistermaat, Jeanine J. | Slagboom, P. Eline
Human Molecular Genetics  2014;23(16):4420-4432.
The genetic contribution to the variation in human lifespan is ∼25%. Despite the large number of identified disease-susceptibility loci, it is not known which loci influence population mortality. We performed a genome-wide association meta-analysis of 7729 long-lived individuals of European descent (≥85 years) and 16 121 younger controls (<65 years) followed by replication in an additional set of 13 060 long-lived individuals and 61 156 controls. In addition, we performed a subset analysis in cases aged ≥90 years. We observed genome-wide significant association with longevity, as reflected by survival to ages beyond 90 years, at a novel locus, rs2149954, on chromosome 5q33.3 (OR = 1.10, P = 1.74 × 10−8). We also confirmed association of rs4420638 on chromosome 19q13.32 (OR = 0.72, P = 3.40 × 10−36), representing the TOMM40/APOE/APOC1 locus. In a prospective meta-analysis (n = 34 103), the minor allele of rs2149954 (T) on chromosome 5q33.3 associates with increased survival (HR = 0.95, P = 0.003). This allele has previously been reported to associate with low blood pressure in middle age. Interestingly, the minor allele (T) associates with decreased cardiovascular mortality risk, independent of blood pressure. We report on the first GWAS-identified longevity locus on chromosome 5q33.3 influencing survival in the general European population. The minor allele of this locus associates with low blood pressure in middle age, although the contribution of this allele to survival may be less dependent on blood pressure. Hence, the pleiotropic mechanisms by which this intragenic variation contributes to lifespan regulation have to be elucidated.
PMCID: PMC4103672  PMID: 24688116
22.  Preschool Weight and Body Mass Index in Relation to Central Obesity and Metabolic Syndrome in Adulthood 
PLoS ONE  2014;9(3):e89986.
If preschool measures of body size routinely collected at preventive health examinations are associated with adult central obesity and metabolic syndrome, a focused use of these data for the identification of high risk children is possible. The aim of this study was to test the associations between preschool weight and body mass index (BMI) and adult BMI, central obesity and metabolic alterations.
The Northern Finland Birth Cohort 1966 (NFBC1966) (N = 4111) is a population-based cohort. Preschool weight (age 5 months and 1 year) and BMI (age 2–5 years) were studied in relation to metabolic syndrome as well as BMI, waist circumference, lipoproteins, blood pressure, and fasting glucose at the age of 31 years. Linear regression models and generalized linear regression models with log link were used.
Throughout preschool ages, weight and BMI were significantly linearly associated with adult BMI and waist circumference. Preschool BMI was inversely associated with high-density lipoprotein levels from the age of 3 years. Compared with children in the lower half of the BMI range, the group of children with the 5% highest BMI at the age of 5 years had a relative risk of adult obesity of 6.2(95% CI:4.2–9.3), of adult central obesity of 2.4(95% CI:2.0–2.9), and of early onset adult metabolic syndrome of 2.5(95% CI:1.7–3.8).
High preschool BMI is consistently associated with adult obesity, central obesity and early onset metabolic syndrome. Routinely collected measures of body size in preschool ages can help to identify children in need of focused prevention due to their increased risk of adverse metabolic alterations in adulthood.
PMCID: PMC3940896  PMID: 24595022
23.  Variation in genes related to hepatic lipid metabolism and changes in waist circumference and body weight 
Genes & Nutrition  2014;9(2):385.
We analysed single nucleotide polymorphisms (SNPs) tagging the genetic variability of six candidate genes (ATF6, FABP1, LPIN2, LPIN3, MLXIPL and MTTP) involved in the regulation of hepatic lipid metabolism, an important regulatory site of energy balance for associations with body mass index (BMI) and changes in weight and waist circumference. We also investigated effect modification by sex and dietary intake. Data of 6,287 individuals participating in the European prospective investigation into cancer and nutrition were included in the analyses. Data on weight and waist circumference were followed up for 6.9 ± 2.5 years. Association of 69 tagSNPs with baseline BMI and annual changes in weight as well as waist circumference were investigated using linear regression analysis. Interactions with sex, GI and intake of carbohydrates, fat as well as saturated, monounsaturated and polyunsaturated fatty acids were examined by including multiplicative SNP-covariate terms into the regression model. Neither baseline BMI nor annual weight or waist circumference changes were significantly associated with variation in the selected genes in the entire study population after correction for multiple testing. One SNP (rs1164) in LPIN2 appeared to be significantly interacting with sex (p = 0.0003) and was associated with greater annual weight gain in men (56.8 ± 23.7 g/year per allele, p = 0.02) than in women (−25.5 ± 19.8 g/year per allele, p = 0.2). With respect to gene–nutrient interaction, we could not detect any significant interactions when accounting for multiple testing. Therefore, out of our six candidate genes, LPIN2 may be considered as a candidate for further studies.
Electronic supplementary material
The online version of this article (doi:10.1007/s12263-014-0385-7) contains supplementary material, which is available to authorized users.
PMCID: PMC3968289  PMID: 24496996
LPIN2; Obesity; Weight gain; Gene–diet interaction
24.  Social Inequalities in Obesity Persist in the Nordic Region Despite Its Relative Affluence and Equity 
Current Obesity Reports  2014;3(1):1-15.
Social inequalities in overweight and obesity (OWOB) have persisted in the affluent and reputedly egalitarian Nordic countries. In this review we examine associations between socioeconomic position (SEP) and OWOB, and secular trends in such associations. Determinants and possible causes of the relations are discussed together with opportunities to cope with OWOB as a public health problem. The findings show a persisting inverse social gradient. An interaction between SEP and gender is noted for adults in Denmark, Finland and Iceland and for children in Sweden. There are overall tendencies for increased inequality, however no consistent trend for an increased social gradient in OWOB. Reasons that increased inequality does not unequivocally mirror in a steepened social gradient in obesity may include methodological questions as well as societal efforts to counteract obesity. Multi-level efforts are needed to prevent OWOB.
PMCID: PMC3920028  PMID: 24533235
Adolescents; Adults; BMI; Children; Denmark; Education; Egalitarian; Finland; Gender; Gini coefficient; Iceland; Income; Inequality; Nordic countries; Norway; Obesity; Obesogenic; Occupation; Overweight; Secular trends; Social gradient; Socioeconomic position; Socioeconomic status; Sweden; Obesity; Social inequalities; Nordic region
25.  Correction: Genetic and Familial Environmental Effects on Suicide – An Adoption Study of Siblings 
PLoS ONE  2014;9(1):10.1371/annotation/41113674-7ca2-42a5-a364-f646ff85c2e7.
PMCID: PMC3883185

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