Examining Nonparticipation in the Maternal Follow-up Within the Danish National Birth Cohort.

A follow-up questionnaire on maternal health was distributed within the Danish National Birth Cohort (established in 1996-2002) 14 years after the index birth. Responses were obtained from 41,466 (53.2%) of 78,010 eligible mothers. To ensure the appropriate use of these data, the possibility of selection bias due to nonparticipation had to be evaluated. We estimated 4 selected exposure-outcome associations (prepregnancy weight-depression; exercise-degenerative musculoskeletal conditions; smoking-heart disease; and alcohol consumption-breast cancer). We adjusted for several factors associated with participation and applied inverse probability weighting. To estimate the degree of selection bias, we calculated relative odds ratios for the relationship between the baseline cohort and the subset participating in the Maternal Follow-up. Participating women were generally healthier, of higher social status, and older than the baseline cohort. However, selection bias in the chosen scenarios was limited; ratios of the odds ratios ranged from -14% to 5% after adjustment for age, parity, social status, and, if the variable was not the exposure variable, prepregnancy body mass index, exercise, smoking, and alcohol consumption. Applying inverse probability weighting did not further reduce bias. In conclusion, while participants differed somewhat from the baseline cohort, selection bias was limited after factors associated with participation status were accounted for.

Maternal weight change from prepregnancy to 7 years postpartum--the influence of behavioral factors.

OBJECTIVE: We studied the influence of maternal behavior on weight change from prepregnancy to 7 years postpartum. METHODS: We used linear regression to study the independent and combined associations between self-reported behavior in pregnancy (dietary intake, leisure-time exercise, sedentary activity, smoking) and postpartum (breastfeeding duration and smoking) on weights at 6 months, 18 months, and 7 years postpartum. RESULTS: Women's average 7-year weight gain was 2.07 kg, with 23% gaining >5 kg. Multivariable analyses suggested that women with healthier dietary intake, more leisure-time exercise, less sedentary behavior, and longer duration of breastfeeding on average gained 1.66 kg [95% confidence interval (CI): 1.40; 1.91] with a significantly reduced odds [OR 0.56 (95% CI: 0.49; 0.64)] of gaining >5 kg from prepregnancy to 7 years postpartum compared to women with none or one of these behaviors [mean gain 3.03 kg (95% CI: 2.68; 3.39)]. Women who ceased smoking had higher long-term weight gain than nonsmokers, but not smokers. CONCLUSIONS: Adherence to healthy behaviors during pregnancy lowered long-term weight gain considerably by lowering postpartum weight retention and subsequent weight gain. Public health efforts to help mothers achieve healthy behaviors might prevent childbearing-related weight gain.

Association of adherence to lifestyle recommendations and risk of colorectal cancer: a prospective Danish cohort study.

OBJECTIVES: To evaluate the association between a simple lifestyle index based on the recommendations for five lifestyle factors and the incidence of colorectal cancer, and to estimate the proportion of colorectal cancer cases attributable to lack of adherence to the recommendations. DESIGN: Prospective cohort study. SETTING: General population of Copenhagen and Aarhus, Denmark. PARTICIPANTS: 55 487 men and women aged 50-64 years at baseline (1993-7), not previously diagnosed with cancer. MAIN OUTCOME MEASURE: Risk of colorectal cancer in relation to points achieved in the lifestyle index (based on physical activity, waist circumference, smoking, alcohol intake, and diet (dietary fibre, energy percentage from fat, red and processed meat, and fruits and vegetables)) modelled through Cox regression. RESULTS: During a median follow-up of 9.9 years, 678 men and women had colorectal cancer diagnosed. After adjustment for potential confounders, each additional point achieved on the lifestyle index, corresponding to one additional recommendation that was met, was associated with a lower risk of colorectal cancer (incidence rate ratio 0.89 (95% confidence interval 0.82 to 0.96). In this population an estimated total of 13% (95% CI 4% to 22%) of the colorectal cancer cases were attributable to lack of adherence to merely one additional recommendation among all participants except the healthiest. If all participants had followed the five recommendations 23% (9% to 37%) of the colorectal cancer cases might have been prevented. Results were similar for colon and rectal cancer, but only statistically significant for colon cancer. CONCLUSIONS: Adherence to the recommendations for physical activity, waist circumference, smoking, alcohol intake, and diet may reduce colorectal cancer risk considerably, and in this population 23% of the cases might be attributable to lack of adherence to the five lifestyle recommendations. The simple structure of the lifestyle index facilitates its use in public health practice.