Regression calibration has been described as a means of correcting effects of measurement error for normally distributed dietary variables. When foods are the items of interest, true distributions of intake are often positively skewed, may contain many zeroes, and are usually not described by well-known statistical distributions. The authors considered the validity of regression calibration assumptions where data are non-Gaussian. Such data (including many zeroes) were simulated, and use of the regression calibration algorithm was evaluated. An example used data from Adventist Health Study 2 (2002–2008). In this special situation, a linear calibration model does (as usual) at least approximately correct the parameter that captures the exposure-disease association in the “disease” model. Poor fit in the calibration model does not produce biased calibrated estimates when the “disease” model is linear, and it produces little bias in a nonlinear “disease” model if the model is approximately linear. Poor fit will adversely affect statistical power, but more complex linear calibration models can help here. The authors conclude that non-Gaussian data with many zeroes do not invalidate regression calibration. Irrespective of fit, linear regression calibration in this situation at least approximately corrects bias. More complex linear calibration equations that improve fit may increase power over that of uncalibrated regressions.
bias (epidemiology); foods; measurement error; power; regression calibration
From a cohort of white, non-Hispanic California Seventh-day Adventists, 99 subjects over age 75 years in 1991 were randomly selected. Dietary habits and educational status had been measured in 1976. Subjects completed the Mini-Mental State Examination (MMSE) in 1991, and at that time, they or caregivers also gave information on current medical problems and drug therapy. Those who ate more calories in 1976 had lower MMSE scores in 1991 (p = 0.03), an association strengthened by excluding those with previous stroke or Parkinson’s disease by 1991. This raises the possibility that higher consumption of calories in middle age may accelerate the decline in cognitive function seen with aging, as apparently occurs in some animals. Less-educated subjects had lower MMSE scores, especially among the very elderly. The statistical model predicts that the negative association between use of psychotropic drugs and MMSE score (p = 0.004) is particularly potent in those cognitively impaired for other reasons. If causal, this suggests that physicians should use these agents very cautiously in such subjects.
caloric intake; dementia; education; psychotropic drugs; Seventh-day Adventists
Evidence of the benefits of soy on cancer risk in Western populations is inconsistent, in part because of the low intake of soy in these groups.
We assessed the validity of soy protein estimates from food-frequency questionnaires (FFQs) in a sample of Adventist Health Study-2 participants with a wide range of soy intakes.
We obtained dietary intake data from 100 men and women (43 blacks and 57 nonblacks). Soy protein estimates from FFQs were compared against repeated 24-h recalls and urinary excretion of daidzein, genistein, total isoflavonoids (TIFLs), and equol (measured by HPLC/photodiode array/mass spectrometry) as reference criteria. We calculated Pearson and Spearman correlation coefficients (with 95% CIs) for FFQ–24-h recall, 24 h-recall–urinary excretion, and FFQ–urinary excretion pairs.
Among soy users, mean (± SD) soy protein values were 12.12 ± 10.80 g/d from 24-h recalls and 9.43 ± 7.83 g/d from FFQs. The unattenuated correlation (95% CI) between soy protein estimates from 24-h recalls and FFQs was 0.57 (0.32, 0.75). Correlation coefficients between soy protein intake from 24-h recalls and urinary isoflavonoids were 0.72 (0.43, 0.96) for daidzein, 0.67 (0.43, 0.91) for genistein, and 0.72 (0.47, 0.98) for TIFLs. Between FFQs and urinary excretion, these were 0.50 (0.32, 0.65), 0.48 (0.29, 0.61), and 0.50 (0.32, 0.64) for daidzein, genistein, and TIFLs, respectively.
Soy protein estimates from questionnaire were significantly correlated with soy protein from 24-h recalls and urinary excretion of daidzein, genistein, and TIFLs. The Adventist Health Study-2 FFQ is a valid instrument for assessing soy protein in a population with a wide range of soy intakes.
Physicians often encounter patients with functional pain disorders such as irritable bowel syndrome (IBS), fibromyalgia (FM), and their co-occurrence. Although these diseases are diagnosed exclusively by patients’ report of symptoms, there are few comparative studies about patients’ perceptions of these diseases.
To compare perceptions of these conditions among 4 groups—3 clinical groups of older women with IBS, FM, or both disorders (IBS plus FM) and 1 similarly aged control group of women with no IBS or FM—using their responses to survey questions about stressful life events, general physical and mental health, and general medical, pain, and psychiatric comorbidities.
Using data from the Biopsychosocial Religion and Health Study survey, responses from women were compared regarding a number of variables. To compare stress-related and physical-mental health profiles across the 4 groups, 1-way analyses of variance and χ2 tests (with Tukey-Kramer and Tukey post hoc tests, respectively) were used, with α set to .05.
The present study comprised 3811 women. Participants in the control group, the IBS group, the FM group, and the IBS plus FM group numbered 3213 (84.3%), 366 (9.6%), 161 (4.2%), and 71 (1.9%), respectively, with a mean (standard deviation) age of 62.4 (13.6), 64.9 (13.7), 63.2 (10.8), and 61.1 (10.9) years, respectively. In general, participants in the control group reported fewer lifetime traumatic and major life stressors, better physical and mental health, and fewer comorbidities than respondents in the 3 clinical groups, and these differences were both statistically significant and substantial. Respondents with IBS reported fewer traumatic and major life stressors and better health (ratings and comorbidity data) than respondents with FM or respondents with IBS plus FM. Overall, respondents with both diseases reported the worst stressors and physical-mental health profiles and reported more diagnosed medical, pain, and psychiatric comorbidities.
The results revealed statistically significant, relatively large differences in perceptions of quality of life measures and health profiles among the respondents in the control group and the 3 clinical groups.
To identify correlates of perceived pain-related restrictions in a community sample of women with fibromyalgia.
The fibromyalgia group was composed of white women with a self-reported, physician-given fibromyalgia diagnosis (N = 238) from the Biopsychosocial Religion and Health Study (BRHS). BRHS respondents had participated in the larger Adventist Health Study-2. To identify associations with pain-related restrictions, we used hierarchical linear regression. The outcome measure was subjects' pain-related restrictions (one SF-12 version 2 item). Predictors included age, education, body mass index (BMI), sleep apnea, and fibromyalgia treatment in the last year, as well as standardized measures for trauma, major life stress, depression, and hostility. To better interpret the findings, pain-related restrictions also were predicted in women with osteoarthritis and no fibromyalgia.
Women with fibromyalgia reporting the more severe pain-related restrictions were those who had experienced trauma accompanied by physical pain, were older, less educated, more depressed, more hostile, had high BMI scores, and had been treated for fibromyalgia in the last 12 months (adjusted R2 = 0.308). Predictors in women with osteoarthritis were age, BMI, treatment in the last 12 months, experience of a major life stressor, and greater depression symptom severity (adjusted R2 = 0.192).
In both groups, age, BMI, treatment in the last 12 months, and depression predicted pain-related restrictions. Experience of a traumatic event with physical pain was the strongest predictor in the fibromyalgia group. These findings may be useful in constructing novel treatments and prevention strategies for pain-related morbidity in fibromyalgia patients.
Fibromyalgia; Osteoarthritis; Pain; Central Nervous System; Trauma; Stress
In a group of 46,000 North-American Adventist women aged 40 and above, we investigated the relationships between body mass index (BMI, kg/m2) at age 20 and the proportion of women who reported at least one miscarriage, periods with irregular menstruation or failing to become pregnant even if trying for more than one straight year. Approximately 31, 14 and 17 %, respectively, reported the three different problems related to reproduction. Positive age- and marital status adjusted relationships were found between BMI at age 20 and periods with irregular menstruation or failing to become pregnant even if trying for more than 1 year, but not with the risk of miscarriages. Women with BMI ≥ 32.5 kg/m2 when aged 20 had approximately 2.0 (95 % CI: 1.6, 2.4) and 1.5 (95 % CI: 1.3, 1.9) higher odds for irregular periods or failing to get pregnant, respectively, than women with BMI in the 20–24.9 kg/m2 bracket. These relationships were consistently found in a number of strata of the population, including the large proportion of the women who never had smoked or never used alcohol. Underweight (BMI < 18.5 kg/m2) when aged 20 marginally (approximately 15 %) increased the risk of failing to get pregnant within a year. Thus, obesity at age 20 increases the risk of reporting some specific reproductive problems, but not the risk of miscarriages.
Electronic supplementary material
The online version of this article (doi:10.1007/s10654-012-9749-8) contains supplementary material, which is available to authorized users.
Obesity; Menstruation; Abortion, spontaneous; Fertility; Seventh-day adventist
Soy milk has become a popular substitute for dairy milk with important health claims. We hypothesized that soy milk, based on its nutrient composition, was comparable to dairy products and, therefore, beneficial for bone health. To test this hypothesis, we examined the benefit of soy milk and dairy products intake on bone health using broadband ultrasound attenuation (BUA) of the calcaneus. Post-menopausal Caucasian women (n=337) who had completed a lifestyle and dietary questionnaire at enrollment into the AHS-2 had their calcaneal BUA measured two years later. The association between osteoporosis (defined as a T-score <−1.8) and some dietary factors (soy milk, dairy) and selected lifestyle factors was assessed using logistic regression. In a multivariable model adjusted for demographics, hormone use and other dietary factors, osteoporosis was positively associated with age (OR= 1.08, 95%CI: 1.06–1.12) and inversely associated with BMI (OR=0.91, 95% CI: 0.86–0.97) and current estrogen usage (OR=0.27, 95% CI: 0.13–0.56). Compared to women who did not drink soy milk, women drinking soy milk once a day or more had 56% lower odds of osteoporosis (OR= 0.44, 95%CI: 0.20–0.98 (ptrend=0.04). Women whose dairy intake was once a day or more had a 62% reduction in the likelihood of having osteoporosis (OR=0.38, 95%CI: 0.17–0.86)(ptrend=0.02) compared to women whose dairy intake was less than twice a week. Among individual dairy products, only cheese showed an independent and significant protection (OR=0.28, 95%CI: 0.12–0.66)(ptrend=0.004) for women eating cheese more than once per week vs. those who ate cheese less than once a week. We concluded that osteoporosis is inversely associated with soy milk intake to a similar degree as dairy intake after accounting for age, BMI, and estrogen usage.
Soy milk consumption; Dairy products; Bone health; Heel bone; Broadband ultrasound attenuation
Previous work studying vegetarians has often found that they have lower blood pressure (BP). Reasons may include their lower BMI and higher intake levels of fruit and vegetables. Here we seek to extend this evidence in a geographically diverse population containing vegans, lacto-ovo vegetarians and omnivores.
Data are analysed from a calibration sub-study of the Adventist Health Study-2 (AHS-2) cohort who attended clinics and provided validated FFQ. Criteria were established for vegan, lacto-ovo vegetarian, partial vegetarian and omnivorous dietary patterns.
Clinics were conducted at churches across the USA and Canada. Dietary data were gathered by mailed questionnaire.
Five hundred white subjects representing the AHS-2 cohort.
Covariate-adjusted regression analyses demonstrated that the vegan vegetarians had lower systolic and diastolic BP (mmHg) than omnivorous Adventists (β =−6·8, P<0·05 and β = −6·9, P<0·001). Findings for lacto-ovo vegetarians (β = −9·1, P<0·001 and β = −5·8, P<0·001) were similar. The vegetarians (mainly the vegans) were also less likely to be using antihypertensive medications. Defining hypertension as systolic BP > 139 mmHg or diastolic BP > 89 mmHg or use of antihypertensive medications, the odds ratio of hypertension compared with omnivores was 0·37 (95 % CI 0·19, 0·74), 0·57 (95 % CI 0·36, 0·92) and 0·92 (95 % CI 0·50, 1·70), respectively, for vegans, lacto-ovo vegetarians and partial vegetarians. Effects were reduced after adjustment for BMI.
We conclude from this relatively large study that vegetarians, especially vegans, with otherwise diverse characteristics but stable diets, do have lower systolic and diastolic BP and less hypertension than omnivores. This is only partly due to their lower body mass.
Vegetarian diet; Blood pressure
To identify the attitudes and perceptions of Black Seventh-day Adventists regarding health research and the healthcare system in two regions of the United States.
Church members were selected from those who participated in the Adventist Health Study-2 (AHS-2) and those who chose not to participate. Participants were selected from two regions of the United States.
Participants were interviewed in their churches, in their homes, and in the research study office at Loma Linda University. Interviews were done in the Western and Southern regions of the United States.
384 Black Seventh-day Adventists, aged >30 years.
Main Outcome Measures
Responses to the structured interviews from those in the Western region were compared to those in the Southern region.
Those in the Southern region included more elderly subjects; they were more likely to own their home despite earning less; and were more likely to be married. Compared to the Western region participants, we found Southern participants to have greater participation in church activities, greater mistrust of the healthcare system and particular concerns about racial inequalities in care. In contrast, they also reported more positive experiences with their personal healthcare provider than Western participants. Southerners felt that they had greater control over their own health, perhaps in part due to a greater identification with the health teachings of the Adventist church.
A number of clear differences were found between Black Adventist subjects living in either the Western or Southern regions of the United States. These factors should be considered carefully when planning the promotion for a research study.
African Americans; Trust; Quality of Health care; Research Subjects; Self-disclosure; Refusal to Participate
To assess race-specific validity of food and food group intakes measured using an FFQ.
Calibration study participants were randomly selected from the Adventist Health Study-2 (AHS-2) cohort by church, and then by subject-within-church. Intakes of forty-seven foods and food groups were assessed using an FFQ and then compared with intake estimates measured using six 24 h dietary recalls (24HDR). We used two approaches to assess the validity of the questionnaire: (i) cross-classification by quartile and (ii) de-attenuated correlation coefficients.
Seventh-day Adventist church members geographically spread throughout the USA and Canada.
Members of the AHS-2 calibration study (550 whites and 461 blacks).
The proportion of participants with exact quartile agreement in the FFQ and 24HDR averaged 46% (range: 29–87%) in whites and 44% (range: 25–88%) in blacks. The proportion of quartile gross misclassification ranged from 1 % to 11 % in whites and from 1 % to 15% in blacks. De-attenuated validity correlations averaged 0·59 in whites and 0·48 in blacks. Of the forty-seven foods and food groups, forty-three in whites and thirty-three in blacks had validity correlations >0·4.
The AHS-2 questionnaire has good validity for most foods in both races; however, validity correlations tend to be higher in whites than in blacks.
Epidemiological methods; Ethnic groups; Questionnaires; Validation studies
The effect of overweight and obesity on the risk of fatal disease tends to attenuate with age. To evaluate whether this effect is partly attributable to disease-related weight loss, we examined the prebaseline history of weight loss and diseases associated with weight loss among adults enrolled in a cohort study. We conducted an analysis of 7,855 adult cohort members of the Adventist Health Study (AHS) I who had provided anthropometric data on surveys at baseline and 17 years prior to baseline. Among adults in the recommended range of BMI (19–25 kg/m2) at baseline we found that: (i) the prevalence of prebaseline weight loss of 5 kg/m2 from an overweight or obese state was 20.4% and increased with age (12.6% for <65 years; 27.7% for 65–84 years; 36.7% for >85 years) and (ii) prebaseline weight loss of 5 kg/m2 from an overweight or obese state was associated with diabetes (odds ratio (OR) = 2.91 95% confidence interval (CI) = (2.16, 3.93)), coronary heart disease (OR = 1.84 95% CI = (1.42, 2.40)), and high blood pressure (OR = 1.51 95% CI = (1.26, s1.82)). During 12 years of follow-up, we found evidence that hazard ratios for adiposity can be confounded by disease-related weight loss. Our findings raise the possibility that prebaseline weight loss can confound the estimation of risk due to adiposity at baseline in a cohort study.
To develop algorithms predicting serum 25 hydroxyvitamin D [s25(OH)D] for a large epidemiological study whose subjects come from large geographic areas, are racially diverse and have a wide range in age, skin types, and month of blood sample collection. This will allow a regression calibration approach to determine s25(OH)D levels replacing the more costly method of collection and analysis of blood samples.
Study design and setting
Questionnaire data from a sub-sample of 236 non-Hispanic whites (whites) and 209 blacks from the widely dispersed Adventist Health Study-2 (n = 96,000) were used to develop prediction algorithms for races separately and combined. A single blood sample was collected from each subject, at different times throughout the year.
Models with independent variables age, sex, BMI, skin type, UV season, erythemal zone, total dietary vitamin D intake, and sun exposure factor explained 22 and 31% of the variance of s25(OH)D levels in white and black populations, respectively (42% when combined). UV season and erythemal zone determined from measured UV radiation produced models with higher R2 than season and latitude.
Combining races with a term for race and using variables with measured UV radiation capture the variance in s25(OH)D levels better than analyzing races separately.
Cancer; Serum 25-hydroxyvitamin D; Predictors; Adventist health study-2; Blacks; Whites
To validate a 204-item quantitative FFQ for measurement of nutrient intake in the Adventist Health Study-2 (AHS-2).
Calibration study participants were randomly selected from the AHS-2 cohort by church, and then subject-within-church. Each participant provided two sets of three weighted 24 h dietary recalls and a 204-item FFQ. Race-specific correlation coefficients (r), corrected for attenuation from within-person variation in the recalls, were calculated for selected energy-adjusted macro- and micronutrients.
Adult members of the AHS-2 cohort geographically spread throughout the USA and Canada.
Calibration study participants included 461 blacks of American and Caribbean origin and 550 whites.
Calibration study subjects represented the total cohort very well with respect to demographic variables. Approximately 33 % were males. Whites were older, had higher education and lower BMI compared with blacks. Across fifty-one variables, average deattenuated energy-adjusted validity correlations were 0·60 in whites and 0·52 in blacks. Individual components of protein had validity ranging from 0·40 to 0·68 in blacks and from 0·63 to 0·85 in whites; for total fat and fatty acids, validity ranged from 0·43 to 0·75 in blacks and from 0·46 to 0·77 in whites. Of the eighteen micronutrients assessed, sixteen in blacks and sixteen in whites had deattenuated energy-adjusted correlations ≥0·4, averaging 0·60 and 0·53 in whites and blacks, respectively.
With few exceptions validity coefficients were moderate to high for macronutrients, fatty acids, vitamins, minerals and fibre. We expect to successfully use these data for measurement error correction in analyses of diet and disease risk.
Epidemiological methods; Ethnic groups; Questionnaires; Validation studies
Missing data are a common problem in nutritional epidemiology. Little is known of the characteristics of these missing data, which makes it difficult to conduct appropriate imputation.
We telephoned, at random, 20% of subjects (n = 2091) from the Adventist Health Study–2 cohort who had any of 80 key variables missing from a dietary questionnaire. We were able to obtain responses for 92% of the missing variables.
We found a consistent excess of “zero” intakes in the filled-in data that were initially missing. However, for frequently consumed foods, most missing data were not zero, and these were usually not distinguishable from a random sample of nonzero data. Older, black, and less-well-educated subjects had more missing data. Missing data are more likely to be true zeroes in older subjects and those with more missing data. Zero imputation for missing data may create little bias except for more frequently consumed foods, in which case, zero imputation will be suboptimal if there is more than 5%–10% missing.
Although some missing data represent true zeroes, much of it does not, and data are usually not missing at random. Automatic imputation of zeroes for missing data will usually be incorrect, although there is a little bias unless the foods are frequently consumed. Certain identifiable subgroups have greater amounts of missing data, and require greater care in making imputations.
The study objective was to compare dietary patterns in their relationship with metabolic risk factors (MRFs) and the metabolic syndrome (MetS).
RESEARCH DESIGN AND METHODS
Cross-sectional analysis of 773 subjects (mean age 60 years) from the Adventist Health Study 2 was performed. Dietary pattern was derived from a food frequency questionnaire and classified as vegetarian (35%), semi-vegetarian (16%), and nonvegetarian (49%). ANCOVA was used to determine associations between dietary pattern and MRFs (HDL, triglycerides, glucose, blood pressure, and waist circumference) while controlling for relevant cofactors. Logistic regression was used in calculating odds ratios (ORs) for MetS.
A vegetarian dietary pattern was associated with significantly lower means for all MRFs except HDL (P for trend < 0.001 for those factors) and a lower risk of having MetS (OR 0.44, 95% CI 0.30–0.64, P < 0.001) when compared with a nonvegetarian dietary pattern.
A vegetarian dietary pattern is associated with a more favorable profile of MRFs and a lower risk of MetS. The relationship persists after adjusting for lifestyle and demographic factors.
The purpose of the study was to investigate the association between incident self-reported fibromyalgia (FM) and prior somatic diseases, lifestyle factors and health behaviors among 3,136 women who participated in two cohort studies 25–26 years apart (the Adventist Health Study 1 and 2). The women completed a comprehensive lifestyle and medical history questionnaire at baseline in 1976. Information on new diagnosis of doctor-told FM was obtained at the 2nd survey in 2002. A total of 136 women reported a diagnosis of FM during 25 years of follow-up, giving a period incidence of 43/1,000 or 1.72/1000 per year. In multivariable logistic regression analyses, a significant, dose-response association was found with number of allergies with OR of 1.61 (95% CI:0.92–2.83) and 3.99 (95% CI:2.31–6.88), (p[trend]<0.0001, respectively, for 1 and 2 or more allergies versus none. A history of hyperemesis gravidarum was also associated with FM with OR of 1.32 (95% CI:0.75–2.32) and 1.73 (95% CI:0.99–3.03), (p[trend]<0.05), respectively, for some or all pregnancies versus none. A positive association with smoking was also found with OR of 2.37 (95% CI:1.33–4.23) for ever smokers versus never smokers. No significant association was found with number of surgeries, history of peptic ulcer or taking medications to control various symptoms.
Fibomyalgia; allergy; hyperemesis gravidarum; smoking; Adventist Health Study
The goal of the prospective Adventist Health Study-2 (AHS-2) was to examine the relationship between diet and risk of breast, prostate and colon cancers in Black and White participants. This paper describes the study design, recruitment methods, response rates, and characteristics of Blacks in the AHS-2, thus providing insights about effective strategies to recruit Blacks to participate in research studies.
We designed a church-based recruitment model and trained local recruiters who used various strategies to recruit participants in their churches. Participants completed a 50-page self-administered dietary and lifestyle questionnaire.
Participants are Black Seventh-day Adventists, aged 30–109 years, and members of 1,209 Black churches throughout the United States and Canada.
Approximately 48,328 Blacks from an estimated target group of over 90,000 signed up for the study and 25,087 completed the questionnaire, comprising about 26% of the larger 97,000 AHS-2-member cohort. Participants were diverse in age, geographic location, education, and income. Seventy percent were female with a median age of 59 years.
In spite of many recruitment challenges and barriers, we successfully recruited a large cohort whose data should provide some answers as to why Blacks have poorer health outcomes than several other ethnic groups, and help explain existing health disparities.
Blacks; African Americans; Cohort Study; Cancer; Recruitment; Adventists
The contribution of stress to the pathophysiology of fibromyalgia has been the subject of considerable debate. The primary purpose of the present study was to evaluate the relationship between traumatic and major life stressors and a fibromyalgia diagnosis in a large group of older women and men. Data were from the federally-funded Biopsychosocial Religion and Health Study, and subjects were 10,424 of the 10,988 survey respondents—two-thirds women and one-third men—providing responses to a fibromyalgia question. Average age was 61.0 ± 13.5 years. A physician-given fibromyalgia diagnosis in a subject’s lifetime was reported by 3.7% of the sample, 4.8% of the women and 1.3% of the men. In two multivariable logistic regression models (all respondents and women only, controlling for age, sex, race/ethnicity, and education), two traumatic experience types (sexual and physical assault/abuse) were associated with a fibromyalgia diagnosis. Two other trauma types (life-threatening and emotional abuse/neglect) and major life stress experiences were not. The highest odds ratios in both models were those for sexual assault/abuse followed by physical assault/abuse. The relationship between age and fibromyalgia was curvilinear in both models (odds ratios rising until approximately age 63 and declining thereafter). In the all-subjects model, being a woman increased the odds of a fibromyalgia diagnosis, and in both models, fibromyalgia was associated with being White (versus non-White) and lower education. We recommend that researchers investigate the relationship between stress and fibromyalgia in concert with genetic and biomarker studies.
Fibromyalgia; Trauma; Stress; Sexual abuse; Physical abuse
Relying on self-reported anthropometric data is often the only feasible way of studying large populations. In this context, there are no studies assessing the validity of anthropometrics in a mostly vegetarian population. The objective of this study was to evaluate the validity of self-reported anthropometrics in the Adventist Health Study 2 (AHS-2).
We selected a representative sample of 911 participants of AHS-2, a cohort of over 96,000 adult Adventists in the USA and Canada. Then we compared their measured weight and height with those self-reported at baseline. We calculated the validity of the anthropometrics as continuous variables, and as categorical variables for the definition of obesity.
On average, participants underestimated their weight by 0.20 kg, and overestimated their height by 1.57 cm resulting in underestimation of body mass index (BMI) by 0.61 kg/m2. The agreement between self-reported and measured BMI (as a continuous variable), as estimated by intraclass correlation coefficient, was 0.97. The sensitivity of self-reported BMI to detect obesity was 0.81, the specificity 0.97, the predictive positive value 0.93, the predictive negative value 0.92, and the Kappa index 0.81. The percentage of absolute agreement for each category of BMI (normoweight, overweight, and obese) was 83.4%. After multivariate analyses, predictors of differences between self-reported and measured BMI were obesity, soy consumption and the type of dietary pattern.
Self-reported anthropometric data showed high validity in a representative subsample of the AHS-2 being valid enough to be used in epidemiological studies, although it can lead to some underestimation of obesity.
Sporadic intake and short half lives of serum or urinary biomarkers may make serum and urinary isoflavones quite unreliable indicators of longer-term dietary soy intake.
In 26 Adventist Health Study-2 (AHS-2) participants we obtained two measures of fasting morning serum isoflavones, 1–2 years apart. In another 76 subjects we obtained an overnight urine sample, and six 24 hour dietary recalls over a period encompassing the time of the urine sample.
Intra-class correlations (ICC) values for serum isoflavones were 0.11 (log[daidzein]) and 0.28 (log[genistein]). Assuming that the correlation(true dietary intake, true urinary excretion)<0.90, it is shown that this implies an ICC for urinary estimates that exceeds 0.56. As expected, the previous day’s soy intake, and its timing, influenced the next morning’s serum levels.
These results suggest that fasting morning serum isoflavone estimates will provide a poor index of long-term soy intake, but that overnight urinary estimates perform much better.
Isoflavones; Reliability; Intra-class correlations; Seventh-day Adventists
We assessed the prevalence of type 2 diabetes in people following different types of vegetarian diets compared with that in nonvegetarians.
RESEARCH DESIGN AND METHODS
The study population comprised 22,434 men and 38,469 women who participated in the Adventist Health Study-2 conducted in 2002–2006. We collected self-reported demographic, anthropometric, medical history, and lifestyle data from Seventh-Day Adventist church members across North America. The type of vegetarian diet was categorized based on a food-frequency questionnaire. We calculated odds ratios (ORs) and 95% CIs using multivariate-adjusted logistic regression.
Mean BMI was lowest in vegans (23.6 kg/m2) and incrementally higher in lacto-ovo vegetarians (25.7 kg/m2), pesco-vegetarians (26.3 kg/m2), semi-vegetarians (27.3 kg/m2), and nonvegetarians (28.8 kg/m2). Prevalence of type 2 diabetes increased from 2.9% in vegans to 7.6% in nonvegetarians; the prevalence was intermediate in participants consuming lacto-ovo (3.2%), pesco (4.8%), or semi-vegetarian (6.1%) diets. After adjustment for age, sex, ethnicity, education, income, physical activity, television watching, sleep habits, alcohol use, and BMI, vegans (OR 0.51 [95% CI 0.40–0.66]), lacto-ovo vegetarians (0.54 [0.49–0.60]), pesco-vegetarians (0.70 [0.61–0.80]), and semi-vegetarians (0.76 [0.65–0.90]) had a lower risk of type 2 diabetes than nonvegetarians.
The 5-unit BMI difference between vegans and nonvegetarians indicates a substantial potential of vegetarianism to protect against obesity. Increased conformity to vegetarian diets protected against risk of type 2 diabetes after lifestyle characteristics and BMI were taken into account. Pesco- and semi-vegetarian diets afforded intermediate protection.
Evidence suggesting that a diet high in fruits and vegetables may be beneficial to bone health has sparked interest in the potential benefit of a vegetarian diet. However, other studies have raised a question regarding the of adequacy protein in such a diet.
The aim of the present study was to take a whole foods approach in examining the effects of foods high in protein on the risk of wrist fracture (WF) in a cohort with a significant proportion consuming a meat-free diet.
A cohort study of women who completed two lifestyle surveys 25 years apart.
One thousand eight hundred and sixty-five peri- and postmenopausal women at the time of the first survey.
There was a significant interaction between meat consumption and foods high in vegetable protein. Among vegetarians, those who consumed the least vegetable protein intake were at highest risk for fracture. However, increasing levels of plant-based high-protein foods decreased WF risk, with a 68% reduction in risk (hazard ratio (HR) = 0.32, 95% confidence interval (CI) 0.13-079) in the highest intake group. Among those with lowest vegetable protein consumption, increasing meat intake decreased the risk of WF, with the highest consumption decreasing risk by 80% (HR = 0.20, 95% CI 0.06-0.66).
The finding that higher consumption frequencies of foods rich in protein were associated with reduced WF supports the importance of adequate protein for bone health. The similarity in risk reduction by vegetable protein foods compared with meat intake suggests that adequate protein intake is attainable in a vegetarian diet.
Dietary protein; Meat; Vegiterian diet; Wrist fracture; Survival cohort; Adventist
The morbidity and mortality of the cardiovascular diseases is high in the developed countries. The lifestyle changes are capable to decrease it by 50%. The aim of the present study was to measure the parameters of some risk factors before and after a one-week NEW START rehabilitative retreat. 1,349 volunteers, 320 men, 1,029 woman, mean age 51±14.5 (SD) years participated in 30 rehabilitative retreats from 1999–2006 in the Czech Republic, using a low-fat, low-energy, lacto-ovo-vegetarian diet and exercise, in a stress-free environment. Body weight, height, BMI, blood pressure, heart rate, serum cholesterol and blood glucose were measured. Body weight decreased in 1,223 measured persons from 71.2±14.38 (SD) to 70.6±14.02 kg (p<0.0001), BMI (1,046 measured persons) from 25.1±4.60 (SD) to 24.8±4.49 (SD) kg/m2 (p<0.0001), systolic blood pressure (1,218 persons) from 129.8±23.02 (SD) to 123.8±21.52 (SD) mmHg (p<0.0001), diastolic blood pressure (1,210 persons) from 79.8±12.7 (SD) to 77.5±11.6 (SD) mmHg (p<0.0001), serum cholesterol (998 persons) from 4.86±0.95 (SD) to 4.32±0.77 (SD) mmol (p<0.0001), blood glucose (544 persons) from 4.31±1.59 (SD) to 3.88±1.33 (SD) mmol (p<0.0001). Heart rate was not significantly decreased. The parameters were lower in lacto-ovo vegetarians and Seventh-day Adventists than in controls who never observed the diet and avail the lifestyle programs. The parameters were nonsignificantly changed one year after finishing the retreat in the sample of 68 persons showing the positive effect of retreats. Our results showed, that the intake of a low-fat, low-energy diet, over the course of one week in a stress-free environment, had positive impact on the risk factors of cardiovascular diseases.
cardiovascular diseases; decrease in risk factors; rehabilitative retreats; lifestyle; lacto-ovo vegetarians; Seventh-day Adventists
Black art posters were offered to replace or augment the established $10 incentive for questionnaire completion in a longitudinal cohort study.
81 churches located in the US southern region were divided between two intervention groups, with a control group of 24 churches from the same region. Primary outcome measures were study enrollment rates and questionnaire return rates between December 2003 and July 2004 as a proportion of church goal.
9.3% of participants returning questionnaires selected a poster in preference to $10. Half of participants offered both monetary and art incentives indicated a poster selection. Crude questionnaire return rates were 57.4% for the pooled intervention churches and 38.2% for the control churches. Enrollment rates among those offered both incentives were significantly higher (p<0.01) than when monetary incentives alone were offered after adjustment for church size, promotional dates, and average income of church members. Survey return rates were also higher in the churches offered both incentives (p=0.04).
These data suggest that the black art posters improved study enrollment and survey return rates. The relatively low rate of poster selection suggests that the art primarily influenced participation indirectly, by creating a more culturally inclusive image of the study.
recruitment; minority; ethnic; African American; research; cohort study