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1.  Do Static and Dynamic Insulin Resistance Indices Perform Similarly in Predicting Pre-diabetes and Type 2 Diabetes? 
We designed a study to compare the predictive power of static and dynamic insulin resistance indices for categorized pre-diabetes (PDM) / type 2 diabetes (DM).
Participants included 1,134 adults aged 18-60 years old with normal glucose at baseline who completed both baseline and 6-years later follow-up surveys. Insulin resistance indices from baseline data were used to predict risk of PDM or DM at follow-up. Two static indices and two dynamic indices were calculated from oral glucose tolerance test results (OGTT) at baseline. Area under the receiver operating characteristic curve (AROC) analysis was used to estimate the predictive ability of candidate indices to predict PDM/DM. A general estimation equation (GEE) model was applied to assess the magnitude of association of each index at baseline with the risk of PDM/DM at follow-up.
The dynamic indices displayed the largest and statistically predictive AROC for PDM/DM diagnosed either by fasting glucose or by postprandial glucose. The bottom quartiles of the dynamic indices were associated with an elevated risk of PDM/DM vs. the top three quartiles. However, the static indices only performed significantly to PDM/DM diagnosed by fasting glucose.
Dynamic insulin resistance indices are stronger predictors of future PDM/DM than static indices. This may be because dynamic indices better reflect the full range of physiologic disturbances in PDM/DM.
PMCID: PMC4138243  PMID: 24882014
insulin resistance indices; predict; pre-diabetes; type 2 diabetes; Chinese; twin; adult
2.  Age, Arterial Stiffness, and Components of Blood Pressure in Chinese Adults 
Medicine  2014;93(29):e262.
Supplemental Digital Content is available in the text
Blood pressure (BP) changes with age. We conducted a cross-sectional study in rural Chinese adults to investigate: (1) what is the relationship between age, arterial stiffness, and BP in Chinese men and women; and (2) to what degree can the age–BP relationship be explained by arterial stiffness, controlling for other covariables.
These analyses included a total of 1688 subjects (males/females: 623/1065), aged 40 to 88 years. Among them, 353 (20.9%) had hypertension (defined as systolic blood pressure (SBP) ≥140 mm Hg or diastolic blood pressure (DBP) ≥90 mm Hg). Arterial stiffness was measured by brachial–ankle pulse wave velocity (baPWV).
baPWV appeared to be more strongly correlated with BP (including SBP, DBP, mean arterial pressure [MAP], pulse pressure [PP]) than age (P < 0.001 for comparisons between Spearman correlation coefficients). Furthermore, baPWV was associated with BP (including SBP, DBP, MAP, and PP) and risk of hypertension in a dose–response fashion, independent of age; in contrast, the age–BP associations were either attenuated or became negative after adjusting for baPWV.
Arterial stiffness appears to be an independent contributor to hypertension, even after adjusting for age and other covariables. In contrast, age–BP associations became attenuated or negative after adjusting for baPWV. The utility of baPWV as a diagnostic, prognostic, and therapeutic indicator for hypertension warrants further investigation.
PMCID: PMC4602627  PMID: 25546666
3.  Genetic and Environmental Contributions to Phenotypic Components of Metabolic Syndrome: A Population-based Twin Study 
Obesity (Silver Spring, Md.)  2009;17(8):1581-1587.
The increasing prevalence of metabolic syndrome (MS) poses a serious public health problem worldwide. Effective prevention and intervention require improved understanding of the factors that contribute to MS. We analyzed data on a large twin cohort to estimate genetic and environmental contributions to MS and to major MS components and their inter-correlations: waist circumference, systolic and diastolic blood pressure, fasting plasma glucose, triglycerides, and high density lipoprotein cholesterol. We applied structural equation modeling to determine genetic and environmental structure of MS and its major components, using 1,617 adult female twin pairs recruited from rural China. The heritability estimate for MS was 0.42 (95% CI: 0.00–0.83) in this sample with low MS prevalence (4.4%). For MS components, heritability estimates were statistically significant and ranged from 0.13 to 0.64 highest for WC, followed by TG, SBP, DBP, HDL-C, and FPG. HDL-C was mainly influenced by common environmental factors (0.62, 95%CI: 0.58–0.62), while the other five MS components were largely influenced by unique environmental factors (0.32–0.44). Bivariate Cholesky decomposition analysis indicated that the clinical clustering of MS components may be explained by shared genetic and/or environmental factors. Our study underscores the importance of examining MS components as inter-correlated traits, and to carefully consider environmental and genetic factors in studying MS etiology.
PMCID: PMC3766632  PMID: 19407809
metabolic syndrome; twin study; heritability; Chinese
4.  A Common Mutation in DEFB126 Causes Impaired Sperm Function and Subfertility 
Science translational medicine  2011;3(92):92ra65.
A glycosylated polypeptide, β-defensin 126 (DEFB126), derived from the epididymis and adsorbed onto the sperm surface, has been implicated in immunoprotection and efficient movement of sperm in mucosal fluids of the female reproductive tract. Here, we report a sequence variant in DEFB126 that has a 2-nucleotide deletion in the open reading frame, which generates a non-stop mRNA. The allele frequency of this variant sequence is high in both a European (0.47) and a Chinese (0.45) population cohort. Binding of the Agaricus bisporus lectin to the sperm surface glycocalyx was significantly lower in men with the homozygous variant (del/del) genotype than in those with either a del/wt or wt/wt genotype, suggesting an altered sperm glycocalyx with fewer O-linked oligosaccharides in del/del men. Moreover, sperm from the del/del donors exhibited an 84% reduction in the rate of penetration of a hyaluronic acid (HA) gel, a surrogate for cervical mucus, compared to the other genotypes. This reduction in sperm performance in HA gels was not a result of decreased progressive motility (average curvilinear velocity) or morphological deficits. However, DEFB126 genotype and lectin binding were highly correlated with performance in the penetration assays. In a prospective cohort study of newly married couples who were trying to conceive by natural means, couples were less likely to become pregnant and took longer to achieve a live birth if the male partner was homozygous for the variant sequence. This common sequence variation in DEFB126, and its apparent cause of impaired reproductive function, provides an opportunity to better understand, clinically evaluate, and possibly treat human infertility.
PMCID: PMC3736313  PMID: 21775668
5.  Association of Adiposity Trajectories With Insulin Sensitivity and Glycemic Deterioration 
Diabetes Care  2012;35(7):1506-1512.
To evaluate associations between adiposity trajectories over time and insulin sensitivity and glucose deterioration in a Chinese twin cohort.
This study focused on 341 males and 292 females aged 20–50 years at baseline who had physical clinical examinations and oral glucose tolerance test at two time points with an average of 6 years apart. BMI, waist circumference, percent body fat (PBF), and percent trunk fat (PTF) trajectories were classified into five track groups based on age- and sex-specific tertiles at each visit. We calculated the odds of the insulin sensitivity index(0,120) [ISI(0,120)] or glycemic deterioration at follow-up among five defined trajectories (tertilebaseline → tertilefollow-up) using generalized estimate equation models. Additionally, we applied structural equation models to examine genetic and environmental influences on adiposity, adiposity change over time (ACO), ISI(0,120), and the interrelationships among them.
Participants with stable adiposity (BMI, waist circumference, PBF, and PTF) in the highest tertile or shifting to the highest tertile tended to have the lowest ISI(0,120) at follow-up or experience glycemic deterioration. Genetic factors exerted the major influence on adiposity, but environmental factors unique to each twin contributed more strongly to ISI and ACO. Correlations between adiposity/ACO and insulin sensitivity were mainly due to environmental influences.
When adiposity stays or becomes high, insulin sensitivity falls and risk of glycemic deterioration rises. Additionally, we found that genetic factors exerted the major influence on adiposity, while environmental factors played the principal role for ACO and insulin sensitivity.
PMCID: PMC3379613  PMID: 22596174
6.  Methylenetetrahydrofolate reductase C677T polymorphism is associated with estimated glomerular filtration rate in hypertensive Chinese males 
BMC Medical Genetics  2012;13:74.
Plasma level of total homocysteine (tHcy) is negatively correlated with kidney function in general population. However, the causal mechanism of this correlation is poorly understood. The purpose of this study is to investigate the association of methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphism, which is a major genetic determinant of the plasma tHcy level, with estimated glomerular filtration rate (eGFR) in Chinese.
A total of 18 814 hypertensive patients (6 914 males, 11 900 females) were included in the study.
Association between the eGFR and MTHFR C677T genotype was examined by sex-specific regression analyses. In males, TT genotype was associated with 1.37 ml/min/1.73 m2 decrease in eGFR (p = 0.004) and with an increased risk (OR = 1.32, p = 0.008) for the lowest quintile of eGFR after adjusting for age, BMI, and blood pressures. However, such association was not observed in females (p > 0.05). This association suggests MTHFR C677T polymorphism may play a role in the regulation of eGFR in males.
MTHFR 677 T is a risk allele for decreased kidney function in Chinese males, implicating this gene in the pathogenesis of chronic kidney disease (CKD).
PMCID: PMC3458982  PMID: 22897803
MTHFR C677T polymorphism; eGFR; CKD
7.  Prevalence and Associated Factors of Diabetes and Impaired Fasting Glucose in Chinese Hypertensive Adults Aged 45 to 75 Years 
PLoS ONE  2012;7(8):e42538.
This study examined the prevalence of impaired fasting glucose (IFG) and diabetes and their associated factors in 17,184 Chinese hypertensive adults aged 45–75 years.
A cross-sectional investigation was carried out in a rural area of Lianyungang, China. Previously undiagnosed diabetes [fasting plasma glucose (FPG) ≥7.0mmol/l] and IFG (6.1–6.9mmol/l) were defined based on FPG concentration. Previously diagnosed diabetes was determined on the basis of self-report. Total diabetes included both previously diagnosed diabetes and previously undiagnosed diabetes.
The prevalence of previously diagnosed diabetes, undiagnosed diabetes, and IFG were 3.4%, 9.8%, and 14.1%, respectively. About 74.2% of the participants with diabetes had not previously been diagnosed. In the multivariable logistic-regression model, older age, men, antihypertensive treatment, obesity (BMI ≥25kg/m2), abdominal obesity (waist circumference ≥90cm for men and ≥80cm for women), non-current smoking, a family history of diabetes, higher heart rate, lower physical activity levels, and inland residence (versus coastal) were significantly associated with both total diabetes and previously undiagnosed diabetes. Furthermore, methylene- tetrahydrofolate reductase (MTHFR) 677 TT genotype was an independent associated factor for total diabetes, and current alcohol drinking was an independent associated factor for previously undiagnosed diabetes. At the same time, older age, men, abdominal obesity, non-current smoking, current alcohol drinking, a family history of diabetes, higher heart rate, and inland residence (versus coastal) were important independent associated factors for IFG.
In conclusion, we found a high prevalence of diabetes in Chinese hypertensive adults. Furthermore, about three out of every four diabetic adults were undiagnosed. Our results suggest that population-level measures aimed at the prevention, identification (even if only based on the FPG evaluation), and treatment of diabetes should be urgently taken to overcome the diabetes epidemic in Chinese hypertensive adults.
PMCID: PMC3411819  PMID: 22880024
8.  Organophosphorous pesticide exposures and sperm quality 
Many Americans are exposed to low levels of organophosphorous (OP) pesticides. In is unclear whether these exposures impact sperm production. We investigated whether there was an association between urinary OP insecticide metabolites and sperm concentration and motility in newly married men from a rural area of eastern People’s Republic of China. Ninety-four cases and 95 controls were included based on their median residual value of sperm concentration and motility after adjusting for relevant covariates. Their urine was analyzed for six dialkylphosphate (DAP) compounds. After adjustment for demographic and exposure variables, the odds of being a case were greater (Odds Ratio=1.30, 95% Confidence Interval 1.02-1.65) in men with higher urinary concentrations of dimethylphosphate (DMP) compared to men with lower levels. No significant differences between cases and controls were found among the other DAP concentrations. DMP exposure and sperm concentration and motility should be explored further in environmental exposure studies.
PMCID: PMC3035720  PMID: 20850521
Organophosphorous; Insecticides; Pesticides; Reproduction; Semen quality; Hormones; Chinese; Male
9.  Tracking Blood Glucose and Predicting Prediabetes in Chinese Children and Adolescents: A Prospective Twin Study 
PLoS ONE  2011;6(12):e28573.
We examined the tracking of blood glucose, the development of prediabetes, and estimated their genetic contributions in a prospective, healthy, rural Chinese twin cohort. This report includes 1,766 subjects (998 males, 768 females) aged 6–21 years at baseline who completed a 6-year follow-up study. Oral glucose tolerance test was performed for all subjects at both baseline and follow-up. We found that subjects with low fasting plasma glucose (FPG) or 2 h post-load glucose (PG) levels at baseline tended to remain at the low level at follow-up. Subjects in the top tertile of baseline plasma glucose tended to have a higher risk of developing prediabetes at follow-up compared to the low tertile: in males, 37.6% vs. 27.6% for FPG and 37.2% vs. 25.7% for 2hPG, respectively; in females, 31.0% vs. 15.4% for FPG and 28.9% vs. 15.1% for 2 h PG, respectively. Genetic factors explained 43% and 41% of the variance of FPG, and 72% and 47% for impaired fasting glucose for males and females, respectively; environmental factors substantially contribute to 2hPG status and impaired glucose tolerance. In conclusion, in this cohort of healthy rural Chinese children and adolescents, we demonstrated that both FPG and 2hPG tracked well and was a strong predictor of prediabetes. The high proportion of children with top tertile of blood glucose progressed to prediabetes, and the incidence of prediabetes has a male predominance. Genetic factors play more important role in fasting than postload status, most of which was explained by unique environmental factors.
PMCID: PMC3233591  PMID: 22163315
10.  The patterns of glucose tolerance and insulin resistance among rural Chinese twin children, Adolescents and young adults 
Metabolism: clinical and experimental  2010;59(12):1752-1759.
Pubertal insulin resistance (IR) is well recognized but little data is available for glucose and insulin pattern from a large, unselected lean population. This report describes the age- and gender-specific distributions of glucose tolerance and IR in a rural Chinese twin population. This report includes 4,488 subjects aged 6 to 24 years. The primary variables of interest are fasting plasma glucose (FPG), 2h post-load plasma glucose (2h PG), fasting serum insulin (FSI), 2h post-load insulin (2h PI) and the homeostatic model assessment for IR (HOMA-IR) index. Age- and gender-specific patterns for the primary variables are described using smoothing plot, arithmetic or geometric mean, and percentiles. There is an increase in FPG, 2h PG and IR during puberty (10–19years) and return to pre-puberty level by the age of 20 years. IR peaks around age of 14 years in girls, and 16 years in boys. 2h PG and 2h PI are higher in girls than in boys from early puberty, and the gender differences are more pronounced afterward. Moreover, the prevalence of impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) increase after puberty, and higher in girls than in boys. In this community based, non-obese rural Chinese twin population, we observed gender-specific remarkable pubertal surge of IR and modest increase in plasma glucose as well as increasing prevalence of IFG and IGT with age. Notably, females had higher 2h PG and higher prevalence of IFG and IGT. Our study underscored that adolescence (even more so in females) is a critical period for developing IR and pre-diabetes.
PMCID: PMC2974012  PMID: 20580383
adolescents; glucose tolerance; insulin resistance; Chinese
11.  Association of central adiposity with pre-diabetes and decreased insulin sensitivity in rural Chinese normal and overweight women 
This study investigated whether high central adiposity was associated with pre-diabetes and decreased insulin sensitivity (IS) in both normal weight (BMI < 23 kg/m2) and overweight (BMI ≥ 23) rural Chinese women.
Adipose variables measured by dual energy X-ray absorptiometry (DEXA) (Percent body fat -%BF, percent lower body fat -%LF and percent trunk fat -%TF) and general adipose variables (BMI and waist circumference - WC) were used for examining the association of adiposity with pre-diabetes among 4,071 rural Chinese females aged 20–60 years. Also, the association of adiposity with IS was tested in both normal and overweight women with normal glucose tolerance (NGT).
BMI was highly correlated with %BF and WC, but weakly correlated with %LF and %TF. Both high %TF (top quartile of %TF) and low %LF (lower three quartiles of %LF) were associated with higher prevalence of pre-diabetes in both normal and overweight women. Compared to normal weight women in low %TF, the odds of pre-diabetes were similarly increased for women with high %TF regardless of whether they were overweight (OR (95% CI) = 1.6 (1.3–2.0)) or not (OR (95% CI) = 1.5 (1.2–2.0)). Similarly, among 3,280 women with NGT, high %TF was associated with increased fasting insulin, 2H-OGTT insulin and HOMA-IR regardless of normal or overweight.
Among relatively lean, rural Chinese women, high %TF was associated with increased odds of pre-diabetes and lower IS regardless of normal or overweight.
PMCID: PMC2882526  PMID: 20045140
body fat; adiposity; pre-diabetes; insulin sensitivity; Chinese female
12.  Sleep Patterns Among Rural Chinese Twin Adolescents 
Sleep medicine  2008;10(4):479-489.
To examine sleep patterns and influencing factors (age, gender, Tanner Stage, weekday vs. weekend, and pre-sleep activity) among rural Chinese adolescents.
This is a prospective study among 621 adolescents aged 11–20 years (341 males) using both a questionnaire and sleep diary to obtain bedtime, wake-up time, sleep latency, and total sleep time (TST).
The median TST was 8.6 hours on weekdays and 9.4 hours on weekends. Despite absence of late night social pressure and computers, a U-shaped TST pattern was observed across age and Tanner stage, with a nadir around age 15–16 years or Tanner IV. Bedtimes became progressively later with age and Tanner Stage, while wake-up time was considerably earlier for school students or up to Tanner IV. Later wake-up times and longer TST on weekends were seen in school students, but not in non-school adolescents (>17 years). Pre-sleep activity, like reading or studying, was related to later bedtime, earlier wake-up time, and shorter TST in both genders.
Age, Tanner stage, and pre-sleep activity affected sleep patterns in this sample of rural Chinese adolescents. Later bedtime coupled with earlier wake-up time associated with academic demand appear to be important contributors to sleep loss among school students.
PMCID: PMC2753967  PMID: 18752997
Age; gender; puberty; Tanner stages; sleep patterns; wake-up time; bedtime; total sleep time
13.  Adiposity, serum lipid levels, and allergic sensitization in Chinese men and women 
Obesity and allergic diseases have increased dramatically in recent decades. While adiposity has been associated with asthma, associations with allergic sensitization have been inconsistent.
To examine the association of adiposity and lipid profiles with allergic sensitization.
This study included 1,187 rural Chinese twins (653 men) aged 18-39 years, with skin prick tests (SPT), anthropometric and DEXA-assessed adiposity measures, and lipid assessments. Allergic sensitization was defined as positive SPT to ≥1 allergen (9 foods and 5 aeroallergens tested). We applied gender-stratified generalized estimating equations to assess the association of adiposity and serum lipids with allergic sensitization, and structural equation models to estimate the genetic/environmental influences on any observed associations.
Males had lower percent body fat (%BF) (13.9% vs. 28.8%) but higher rates of allergic sensitization (56.2% vs. 36.7%) than females. Males in the highest %BF quartile were 2.1 times more likely sensitized than the lowest quartile (95%CI 1.3-3.5, P-trend=0.003). In males, the risk of allergic sensitization increased with HDL<40 mg/dl (OR=4.0, 95%CI 1.8-9.2) and higher LDL quartiles (P-trend=0.007). This appeared to be partially explained by shared genetic factors between serum lipid levels and allergic sensitization. In females, lower HDL was associated with increased risk of allergic sensitization.
In this relatively lean Chinese population, higher %BF, lower HDL and higher LDL were associated with greater risk of allergic sensitization, most notable in males. The observed associations between adiposity, serum lipids and allergic sensitization in males appear to be partially explained by common genetic influences on these traits.
PMCID: PMC2697621  PMID: 19135238
DEXA; Body mass index; Adiposity; Serum lipids; Sensitization
14.  Dissociation between the Prevalence of Atopy and Allergic Disease in Rural China among Children and Adults 
The prevalence of allergic diseases is increasing worldwide, but the reasons are not well understood. Previous studies suggest that this trend may be associated with lifestyle and urbanization.
To describe patterns of sensitization and allergic disease in an unselected agricultural Chinese population.
The data was derived from a community-based twin study in Anqing, China. Skin prick testing was performed to foods and aeroallergens. Atopy was defined as sensitization to ≥1 allergen. Allergic disease was ascertained by self-report. The analysis was stratified by sex and age (children [11-17 years] and adults [≥18 years]) and included 1059 same-sex twin pairs.
Of 2118 subjects, 57.6% were male (n=1220). Ages ranged from 11-71 years; 43.3% were children (n=918). Atopy was observed in 47.2% (n=999) of participants. The most common sensitizing foods were shellfish (16.7%) and peanut (12.3%). The most common sensitizing aeroallergens were dust mite (30.6%) and cockroach (25.2%). Birth order and zygosity had no effect on sensitization rates. Multivariate logistic regression models revealed risk factors for sensitization include age for foods and sex for aeroallergens. The rates of food allergy and asthma were estimated to be <1%.
Atopic sensitization was common in this rural farming Chinese population, particularly to shellfish, peanut, dust mite, and cockroach. The prevalence of allergic disease, in contrast, was quite low.
Clinical Implications
Allergen sensitization was far more common than the rate of self-reported allergic disease in this community. Evidence of sensitization is an inadequate marker of allergic disease and better correlates with clinical disease are needed.
Capsule summary
Among this large unselected Chinese rural farming community, atopy was observed in nearly half of the study subjects, but the rate of allergic disease was comparatively very low.
PMCID: PMC2747487  PMID: 18805578
aeroallergens; rural; farming community; Chinese; food allergens; prevalence; sensitization; skin prick tests
15.  Ser1369Ala Variant in Sulfonylurea Receptor Gene ABCC8 Is Associated With Antidiabetic Efficacy of Gliclazide in Chinese Type 2 Diabetic Patients  
Diabetes Care  2008;31(10):1939-1944.
OBJECTIVE—The purpose of this study was to investigate whether genetic variants could influence the antidiabetic efficacy of gliclazide in type 2 diabetic patients.
RESEARCH DESIGN AND METHODS—A total of 1,268 type 2 diabetic patients whose diabetes was diagnosed within the past 5 years and who had no recent hypoglycemic treatment were enrolled from 23 hospitals in China. All of the patients were treated with gliclazide for 8 weeks. Fasting and oral glucose tolerance test 2-h plasma glucose, fasting insulin, and A1C were measured at baseline and after 8 weeks of treatment. We used two independent cohorts to test the associations of 25 single nuclear polymorphisms in 11 candidate genes with the antidiabetic efficacy of gliclazide. A general linear regression model was used to test the association with adjustment for important covariates.
RESULTS—After 8 weeks of gliclazide therapy, mean fasting plasma glucose (FPG) was reduced from 11.1 mmol/l at baseline to 7.7 mmol/l. In cohort 1, we genotyped all 25 SNPs (n = 661) and found that Ser1369Ala of the ABCC8 gene and rs5210 of the KCNJ11 gene were significantly associated with decreases in FPG (P = 0.002). We further genotyped Ser1369Ala in cohort 2 (n = 607) and confirmed the association identified in cohort 1. In the pooled analysis, compared with subjects with the Ser/Ser genotype, subjects with the Ala/Ala genotype had a 7.7% greater decrease in FPG (P < 0.001), an 11.9% greater decrease in 2-h plasma glucose (P = 0.003), and a 3.5% greater decrease in A1C (P = 0.06) after 8 weeks of treatment with gliclazide.
CONCLUSIONS—In two independent cohorts of Chinese type 2 diabetic patients, we found consistent evidence that the Ser1369Ala variant in the ABCC8 gene can influence the antidiabetic efficacy of gliclazide.
PMCID: PMC2551631  PMID: 18599530
16.  Effect of Environmental Tobacco Smoke on Levels of Urinary Hormone Markers 
Environmental Health Perspectives  2005;113(4):412-417.
Our recent study showed a dose–response relationship between environmental tobacco smoke (ETS) and the risk of early pregnancy loss. Smoking is known to affect female reproductive hormones. We explored whether ETS affects reproductive hormone profiles as characterized by urinary pregnanediol-3-glucuronide (PdG) and estrone conjugate (E1C) levels. We prospectively studied 371 healthy newly married nonsmoking women in China who intended to conceive and had stopped contraception. Daily records of vaginal bleeding, active and passive cigarette smoking, and daily first-morning urine specimens were collected for up to 1 year or until a clinical pregnancy was achieved. We determined the day of ovulation for each menstrual cycle. The effects of ETS exposure on daily urinary PdG and E1C levels in a ±10 day window around the day of ovulation were analyzed for conception and nonconception cycles, respectively. Our analysis included 344 nonconception cycles and 329 conception cycles. In nonconception cycles, cycles with ETS exposure had significantly lower urinary E1C levels (β= –0.43, SE = 0.08, p < 0.001 in log scale) compared with the cycles without ETS exposure. There was no significant difference in urinary PdG levels in cycles having ETS exposure (β= –0.07, SE = 0.15, p = 0.637 in log scale) compared with no ETS exposure. Among conception cycles, there were no significant differences in E1C and PdG levels between ETS exposure and nonexposure. In conclusion, ETS exposure was associated with significantly lower urinary E1C levels among nonconception cycles, suggesting that the adverse reproductive effect of ETS may act partly through its antiestrogen effects.
PMCID: PMC1278480  PMID: 15811831
environmental tobacco smoke; estrone conjugates (E1C); pregnanediol-3-glucuronide (PdG); prospective study; urinary hormone levels

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