Parental body size and offspring lung health: preparing for parenthood already in childhood?

Abstract

Background: In parallel with the increase in asthma and allergies there has been a dramatic increase in overweight and obesity during the last decades. Being overweight or obese is a known risk factor for asthma, and overweight and obesity are believed to be detrimental to lung function across age groups regardless of asthma status. However, potential health effects of overweight/obesity for future offspring are not well investigated. While it has been known for quite some time that a mother’s health and behaviour shortly before and during pregnancy may affect her children’s health, emerging evidence suggests that also parents’ health and behaviours before conception – including fathers as well as mothers- could be of importance for the future health of the child. Potential effects of parental overweight for respiratory health in future offspring is not well studied and would require life course data on parental overweight/obesity. Such data are rarely available, and the use of figural body silhouettes from various ages might provide a possibility for retrospectively assessing body size at several time points in the past.

Objectives: (I) Investigate the use of body silhouettes in adults as a tool to reflect past overweight/obesity, validated against previously measured or self-reported height and weight in the European Community Respiratory Health Survey (ECRHS) and the Respiratory Health In Northern Europe (RHINE) study, respectively. (II) Examine whether mothers’ and fathers’ overweight in childhood, adolescence, or adulthood is associated with asthma in their offspring. (III) Investigate whether a parent’s overweight in childhood, adolescence, or adulthood could be a cause of altered lung function in adult offspring.

Material and methods: (I) Data from women and men participating in the second follow up of ECRHS (N= 3041) was used to validate the selected body silhouettes against previously measured height and weight in ECRHS (recall 9-23 years). Data from women and men participating in the first follow up of RHINE (N=3410) was used to validate the selected body silhouettes against previously self-reported height and weight in the initial RHINE study (9-13 years recall). We calculated Spearman correlations between BMI and body silhouettes and ROC-curve analyses for identifying obesity (BMI ≥30).

(II) We included 6347 adult offspring (age 18-52 years) investigated in the Respiratory Health in Northern Europe, Spain, and Australia (RHINESSA) multigeneration study of 2044 fathers and 2549 mothers investigated in ECRHS. Associations of parental overweight status at age 8 years, puberty and age 30 years with offspring’s childhood overweight status and offspring’s asthma with or without nasal allergies were analysed using 2-level logistic regression and 2-level multinomial logistic regression, respectively. Counterfactual-based mediation analyses was performed to establish whether observed associations reflected direct or indirect effects mediated through offspring’s own overweight status.

(III) We included 929 adult offspring (18-54 years, 54% daughters) investigated in the RHINESSA study, of 308 fathers and 388 mothers investigated in the ECRHS or RHINE follow-up studies (2011-2014). Counterfactual-based multi-group mediation analyses by offspring’s sex were used to assess whether the effects of parents’ overweight before puberty on adult offspring’s FEV1, FVC and FEV1/FVC were mediated through offspring’s pre-pubertal overweight and/or adult height, separately within each of the paternal and maternal lines.

Results: (I) Spearman correlations between measured BMI age 30(±2y) and body silhouettes in women and men were between 0.62 and 0.66, and correlations for self-reported BMI ranged from 0.58 to 0.70. The area under the curve for identification of obesity at age 30 using body silhouettes vs previously measured BMI at age 30(±2y) was 0.92 (95% CI 0.87, 0.97) and 0.85 (95% CI 0.75, 0.95) in women and men, respectively; for previously self-reported BMI, 0.92 (95% CI 0.88, 0.95) and 0.90 (95% CI 0.85, 0.96). (II) We found a statistically significant effect of fathers’ onset of overweight in puberty for offspring’s asthma without nasal allergies (relative risk ratio, 2.31 [95% CI, 1.23-4.33]). This effect was direct and not mediated through the offspring’s own overweight status. No effect of mother’s overweight was associated with offspring’s asthma. (III) Fathers’ overweight before puberty had a negative indirect effect, mediated through sons’ height, on sons’ FEV1[beta (95% CI): -144 (-272, -23) mL] and FVC [beta (95% CI): -210 (-380, -34) mL], and a negative direct effect on sons’ FVC [-262 (-501, -9) mL]. Statistically significant effects on FEV1/FVC were not observed. In the maternal line, mothers’ overweight before puberty had neither direct nor indirect effects on offspring’s lung function.

Conclusions: Our study suggests that body silhouettes are a useful epidemiological tool, enabling retrospective differentiation of obesity and non-obesity in adult women and men. Further, our work suggests that metabolic factors long before conception can increase asthma risk and that male puberty is a time window of particular importance for offspring’s health. Finally, we found that fathers’ overweight starting before puberty appear to cause considerably lower FEV1 and FVC in their future sons. These effects could be partly mediated through sons’ adult height, but not through his pre-pubertal overweight.

Implications: We have shown that the metabolic environment in male prepuberty might influence the health of the next generation. Closer scientific attention to male puberty in relation to future generations health may have profound implications and open new opportunities for targeted public health strategies. We speculate that while intervening in the prepuberty age window in one generation we might improve the health of two generations.