Abstract
Emerging evidence suggests that parents' preconception exposures may influence offspring health. We aimed to investigate maternal and paternal smoking onset in specific time windows in relation to offspring body mass index (BMI) and fat mass index (FMI). We investigated fathers (n = 2111) and mothers (n = 2569) aged 39-65 years, of the population based RHINE and ECRHS studies, and their offspring aged 18-49 years (n = 6487, mean age 29.6 years) who participated in the RHINESSA study. BMI was calculated from self-reported height and weight, and FMI was estimated from bioelectrical impedance measures in a subsample. Associations with parental smoking were analysed with generalized linear regression adjusting for parental education and clustering by study centre and family. Interactions between offspring sex were analysed, as was mediation by parental pack years, parental BMI, offspring smoking and offspring birthweight. Fathers' smoking onset before conception of the offspring (onset ≥15 years) was associated with higher BMI in the offspring when adult (β 0.551, 95%CI: 0.174-0.929, p = 0.004). Mothers' preconception and postnatal smoking onset was associated with higher offspring BMI (onset <15 years: β1.161, 95%CI 0.378-1.944; onset ≥15 years: β0.720, 95%CI 0.293-1.147; onset after offspring birth: β2.257, 95%CI 1.220-3.294). However, mediation analysis indicated that these effects were fully mediated by parents' postnatal pack years, and partially mediated by parents' BMI and offspring smoking. Regarding FMI, sons of smoking fathers also had higher fat mass (onset <15 years β1.604, 95%CI 0.269-2.939; onset ≥15 years β2.590, 95%CI 0.544-4.636; and onset after birth β2.736, 95%CI 0.621-4.851). There was no association between maternal smoking and offspring fat mass. We found that parents' smoking before conception was associated with higher BMI in offspring when they reached adulthood, but that these effects were mediated through parents' pack years, suggesting that cumulative smoking exposure during offspring's childhood may elicit long lasting effects on offspring BMI.
Highlights
Maternal smoking during pregnancy plays a significant role in increased risk of obesity and metabolic disorders in the offspring [1,2,3,4]
We considered other covariates, such as parental age, offspring education, the other parent’s smoking habits, and Body mass index (BMI), to be included in the statistical model, as shown in S1 Fig. we did not find these factors likely to confound the relationship between parental smoking onset and offspring BMI, and did not include them in the final models
10% started smoking before age 15 years, 40% started smoking from age 15 years, and 2% started smoking after offspring birth
Summary
Maternal smoking during pregnancy plays a significant role in increased risk of obesity and metabolic disorders in the offspring [1,2,3,4]. Observations from the Overkalix and ALSPAC cohorts showed that excess food supply and smoking during mid-childhood and pre-pubertal years were associated with metabolic and cardiovascular health, and risk of becoming obese in subsequent generation(s) [16,17,18,19]. These findings remain to be successfully replicated, and there exists a possibility of residual confounding due to unmeasured family factors, especially due to the social patterning and inequalities related to smoking behaviour [20, 21]. Analyses of the RHINESSA, RHINE and ECRHS cohorts found that asthma was more common in offspring with fathers who were obese in puberty [22], as well as in offspring with fathers who smoked in adolescent years [23, 24]
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