Residential green space and waist circumference affect telomere shortening in childhood: the longitudinal ChiBS study

BACKGROUND: Telomere shortening, recognised as one of the most well known biomarkers of biological ageing, is susceptible to various environmental and lifestyle factors, encompassed in the exposome. Research shows that telomere length is substantially determined early in life and that exposures in childhood can have important consequences in setting telomere length later in life and thus the lifespan of an individual. We explored the associations between 17 exposures and longitudinal telomere change in a child population. METHODS: Children up to the age of 9 years, from Aalter, Belgium, were enrolled in 2008 and 2010 and followed-up for 5 or 7 years (up to 2015). Relative telomere length was measured at baseline (2008 or 2010) and at follow-up, in 2015, through quantitative real-time PCR. Exposures and lifestyle factors comprised: body-mass index, waist circumference, dietary habits (ie, sugar-rich and fat-rich food intake and vegetables and fruit intake), psychosocial stress (ie, negative events, emotions, and behaviour), sleep duration, physical activity, and residential environmental quality (long-term black carbon and particulate matter exposure and residential green space). Green space was estimated from high-resolution land cover data within several buffers (50-3000 m) around the child's residence. Cross-sectional and longitudinal analyses were done by means of linear regression models, adjusting for length of follow-up, age, sex, and socioeconomic status. Effect size was expressed as β, the standardised regression coefficient of the linear regression, and was calculated by multiplying the unstandardised regression coefficient by the standard deviation of the predictor variable and dividing by the standard deviation of the outcome variable. Written informed consent was obtained from all parents. Children aged 12 years and older also provided written informed consent. Children younger than 12 years gave verbal consent. FINDINGS: 150 children (77 [51%] boys and 73 [49%] girls) aged 2·8-10·3 years (median 5·9 years [IQR 4·9-7·1]) at baseline were included in the longitudinal analysis, which showed that higher residential green space at baseline was associated with inferior telomere shortening (β=0·261; p=0·0018), whereas a higher baseline waist circumference was associated with more telomere attrition (β=-0·287; p=0·0015). These predictors were confirmed via lasso variable selection and correction for multiple testing. In addition, children with more unhealthy exposures had significantly more telomere shortening over the follow-up period than did children with less unhealthy baseline exposures (β=-0·200; p=0·017). INTERPRETATION: Residential green space and waist circumference were identified as predictors of telomere shortening in childhood. These results further showcase the benefits of a healthy lifestyle from an early age and the importance of a green environment in promoting molecular longevity from childhood onwards. FUNDING: Research Foundation Flanders (Brussels, Belgium; project number G073315N).