The Body Mass Index of Adolescents Attending Seventh-Day Adventist Schools in Australia: 2001-2012.

BACKGROUND: We examined the body mass index (BMI) of students attending Seventh-day Adventist (Adventist) schools in Australia in 2001 and 2012. METHODS: A total of 3069 students attending Adventist schools in Australia responded to a health and lifestyle survey in 2001 (N = 1335) and 2012 (N = 1734). The survey captured self-reported height and weight, demographics (age, sex, year level, religion), and select health behaviors. RESULTS: Compared with national norms, lower rates of overweight and obesity were observed in the study cohort, but higher rates of underweight. There was no change in the mean BMI of the students attending Adventist schools in Australia from 2001 to 2012. Regression analyses indicated that a lower BMI was associated with age, sex, more regularly eating breakfast, consuming less soft drink, and having a regular exercise program. The students reported a high consumption of fruits, vegetables, and whole grains compared with Australian national norms, and 29% claimed to be vegetarian. CONCLUSIONS: Students attending Adventist schools appear to have a lower prevalence of overweight and obesity than the secular population, but a higher prevalence of underweight. The mechanisms through which Adventist schools may influence student's BMI warrants further investigation.

Vegetarian dietary patterns and the risk of colorectal cancers.

IMPORTANCE: Colorectal cancers are a leading cause of cancer mortality, and their primary prevention by diet is highly desirable. The relationship of vegetarian dietary patterns to colorectal cancer risk is not well established. OBJECTIVE: To evaluate the association between vegetarian dietary patterns and incident colorectal cancers. DESIGN, SETTING, AND PARTICIPANTS: The Adventist Health Study 2 (AHS-2) is a large, prospective, North American cohort trial including 96,354 Seventh-Day Adventist men and women recruited between January 1, 2002, and December 31, 2007. Follow-up varied by state and was indicated by the cancer registry linkage dates. Of these participants, an analytic sample of 77,659 remained after exclusions. Analysis was conducted using Cox proportional hazards regression, controlling for important demographic and lifestyle confounders. The analysis was conducted between June 1, 2014, and October 20, 2014. EXPOSURES: Diet was assessed at baseline by a validated quantitative food frequency questionnaire and categorized into 4 vegetarian dietary patterns (vegan, lacto-ovo vegetarian, pescovegetarian, and semivegetarian) and a nonvegetarian dietary pattern. MAIN OUTCOMES AND MEASURES: The relationship between dietary patterns and incident cancers of the colon and rectum; colorectal cancer cases were identified primarily by state cancer registry linkages. RESULTS: During a mean follow-up of 7.3 years, 380 cases of colon cancer and 110 cases of rectal cancer were documented. The adjusted hazard ratios (HRs) in all vegetarians combined vs nonvegetarians were 0.78 (95% CI, 0.64-0.95) for all colorectal cancers, 0.81 (95% CI, 0.65-1.00) for colon cancer, and 0.71 (95% CI, 0.47-1.06) for rectal cancer. The adjusted HR for colorectal cancer in vegans was 0.84 (95% CI, 0.59-1.19); in lacto-ovo vegetarians, 0.82 (95% CI, 0.65-1.02); in pescovegetarians, 0.57 (95% CI, 0.40-0.82); and in semivegetarians, 0.92 (95% CI, 0.62-1.37) compared with nonvegetarians. Effect estimates were similar for men and women and for black and nonblack individuals. CONCLUSIONS AND RELEVANCE: Vegetarian diets are associated with an overall lower incidence of colorectal cancers. Pescovegetarians in particular have a much lower risk compared with nonvegetarians. If such associations are causal, they may be important for primary prevention of colorectal cancers.

Missing data in a long food frequency questionnaire: are imputed zeroes correct?

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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 [corrected] little bias unless the foods are frequently consumed. Certain identifiable subgroups have greater amounts of missing data, and require greater care in making imputations.

Recruiting blacks to the Adventist health study: Do follow-up phone calls increase response rates?

PURPOSE: To determine whether follow-up phone calls improve response rates to a long questionnaire among black and white subjects. METHODS: Forty black and 39 white Seventh-day Adventist churches were randomized to experimental or control status in a 2:1 ratio favoring the intervention, which is a follow-up phone call to certain church members. Subjects selected from each church were those who had signed up for the Adventist Health Study-2 but not returned a questionnaire 3 months after promotion began. Further returns from a church over the next 3 months, and this increment as a proportion of baseline response, were assessed using t-tests and Poisson regression, respectively. RESULTS: Comparing black experimental and control churches, the mean difference was 5.5 returned questionnaires per church (p < 0.01). Among white churches the mean difference was 3.0 (ns). The baseline-adjusted increment, however, was greater by a factor of 3.37 (95% confidence interval, 1.92, 5.93) in the black experimental relative to control churches, but among white experimental churches was 13% (ns) lower than controls. This difference in response by ethnic group was statistically significant (p < 0.01). CONCLUSION: Follow-up phone calls improved response rates among black subjects only.