Effect of the exposure to maternal smoking during pregnancy and childhood on the body mass index until adolescence

Cesarean birth and risk of obesity from birth to adolescence: A cohort study

BACKGROUND

Recent studies have shown associations between cesarean birth and overweight. However, very few studies have evaluated weight gain or adiposity throughout life, and the majority are restricted to analysis during childhood. The purpose of this study was to analyze the effect of cesarean birth on obesity risk from birth to adolescence.

METHODS

The study sample was drawn from live births that occurred in 1999 and 2000 in Mato Grosso-Brazil. Participants were evaluated once when they were between 0 and 5 years of age and again after approximately 10 years (2009-2011). To measure the association between cesarean birth and obesity (Body Mass Index/age >+2 z-scores), we used generalized estimation equations (GEE) with binomial distribution and log-binomial models for repeated measures, controlled by the following confounding factors: weight and length at birth, sex, gestational age, breastfeeding, maternal age and schooling, economic class in childhood, and maternal smoking during pregnancy. The exposure-time interaction term was evaluated to verify differences in the change in the risk of obesity over time.

RESULTS

56.8% of children in the sample were born by cesarean birth. Children born by cesarean had a higher risk of obesity from birth through adolescence (RR = 1.22, 95% CI = 1.02; 1.46), even after adjusting for covariates, when compared with those born vaginally. However, the time-exposure interaction term was not significant, which indicates that there was no increased risk of obesity over time.

CONCLUSION

Cesarean birth was positively associated with obesity from birth to adolescence, with a persistent risk in the period evaluated.

Biomedical, psychological, environmental and behavioural factors associated with adult obesity in a nationally representative sample

OBJECTIVE

To identify personality, biomedical and behavioural factors associated with adult obesity in a large longitudinal sample.

METHOD

In total, 5360 participants with data on personality, neurological functioning, maternal smoking during pregnancy, education and occupation, physical exercise, adult self-reported BMI and obesity were included in the study. Obesity at 55 years was the outcome variable.

RESULTS

The rates of obesity increased from 9.5 to 22.8% from age 33 to 55 years. Logistic regression analyses (adjusted estimates) showed that childhood neurological functioning (OR = 1.32: 1.07-1.63, P < 0.01), maternal smoking during pregnancy (OR = 1.42: 1.22-1.65, P < 0.001), educational qualifications (OR = 0.54: 0.37-0.79, P < 0.01), trait conscientiousness (OR = 0.80:0.74-0.86, P < 0.001) and physical exercise (OR = 0.87: 0.82-0.92, P < 0.001) were significant predictors of obesity at age 55 years for both men and women. Trait extraversion for men (OR = 1.16: 1.07-1.26, P < 0.001) and trait emotional stability for women (OR = 0.90: 0.82-0.99, P < 0.05) were also significant predictors of the outcome variable.

CONCLUSION

Biomedical, psychological, environmental and behavioural factors were all associated with adult obesity.