The association between ambient temperature exposure during infancy and overweight at age two years

Abstract

BACKGROUND AND AIM: Childhood overweight and obesity is increasing in prevalence globally and is a risk factor for metabolic disease in adulthood. We have previously described an association between exposure to higher ambient temperatures during infancy and rapid infant weight gain. We aimed to examine the association between ambient temperature exposure during the first year of life and overweight at age two years. METHODS: A population-based cohort study using data from the Israeli network of public maternal and child health clinics from 2011 to 2018. The study population was restricted to children born with birthweight ≥2500g (N=579,404). We assessed exposure to ambient temperature using a high-resolution spatio-temporal model and calculated the average annual exposure during the first year of life for each infant based on daily temperature at their address. Overweight at two years was defined as >85th percentile in World Health Organization age and sex-adjusted body mass index. We calculated relative risks using log-linear models and fitted general additive models with thin plate regression splines while adjusting for sub-district, neighbourhood socio-economic index, ethnicity, month and year of birth and average ambient temperature during pregnancy. RESULTS: We found a positive association between ambient temperature exposure and risk of overweight at age two years. Children exposed to the highest temperature quintile (≥22.0°C) had an adjusted relative risk of 1.16 (95% CI 1.12, 1.19) compared to those exposed to the lowest quintile (<19.6°C). Modelling temperature as a continuous variable using general additive models showed an increase in risk with higher temperature exposure up to approximately 23°C when the risk levelled out. CONCLUSIONS: Exposure to higher ambient temperatures during infancy is associated with increased risk of overweight at age two years in Israel. Future studies should explore this association in other populations and examine possible biological mechanisms. KEYWORDS: temperature, child health, climate