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Telomeres are vulnerable to various environmental exposures and lifestyle factors, encompassed in the exposome. Recent research shows that telomere length is substantially determined early in life and that exposures in childhood may have important consequences in setting later life telomere length. We explore in a child population the associations of 17 exposures with telomere length and longitudinal telomere change. Children (2.8–10.3y at baseline, 51.3% boys) were followed-up for five to seven years. Relative telomere length was measured at baseline and follow-up using quantitative real-time PCR. Exposures and lifestyle factors included: body composition (body mass index and waist circumference), dietary habits (sugar- and fat-rich food intake, vegetables and fruit intake), psychosocial stress (events, emotions, behaviour), sleep duration, physical activity, and residential environmental quality (longterm black carbon, particulate matter exposure, and residential green space). Cross-sectional (n=182) and longitudinal (n=150) analyses were assessed using linear regression models, adjusting for age, sex, socioeconomic status and multiple testing. Our longitudinal analyses showed that higher residential green space at baseline was associated with (β=0.261, p=0.002) lower telomere attrition and that children with a higher waist circumference at baseline showed a higher telomere attrition (β=−0.287, p=0.001). These two predictors were confirmed via LASSO variable selection and correction for multiple testing. In addition, children with more unhealthy exposures at baseline had a significantly higher telomere attrition over the follow-up period compared to children with more healthy exposures (β=−0.200, p=0.017). Waist circumference and residential green space were identified as predictors associated with telomere attrition in childhood. These results further support the advantages of a healthy lifestyle from early age onwards and the importance of a green environment to promote molecular longevity from childhood onwards. • Telomere attrition over 5-7y and 17 exposures were measured in 4-7y old children. • More unhealthy exposures at baseline resulted in higher telomere attrition. • Residential green space at baseline was associated with lower telomere attrition. • Waist circumference partially mediated this association. • Lifestyle and green space during childhood seems important for molecular longevity. [ABSTRACT FROM AUTHOR]

Air pollution exposure is a major global health concern and has been associated with molecular aging. Unfortunately, the situation has not received much attention in the African region. The aim of this study was to investigate whether current personal ambient NO 2 and benzene, toluene, ethyl-benzene and xylenes (ortho (o)-, meta (m)- and para (p)-xylene (BTEX) exposure is associated with leukocyte telomere length (LTL), a marker of molecular ageing, in apparently healthy women (mean ± SD age: 42.5 ± 13.4 years) residing in the Cape Town region of South Africa. The repeated measures study collected data from 61 women. Seven-day median (interquartile range (IQR)) personal NO 2 and BTEX exposure levels were determined via compact passive diffusion samplers carried on the person prior to baseline (NO 2 : 14.2 (9.4–17.2) μg/m³; Benzene: 3.1 (2.1–5.3) μg/m³) and 6-month follow-up (NO 2 : 10.6 (6.6–13.6) μg/m³; Benzene: 2.2 (1.3–4.9) μg/m³) visits. LTL was measured at baseline and follow-up using a real-time PCR method. Multiple linear mixed model analyses (adjusting for age, body mass index, smoking, employment status, level of education and assessment visit) showed that each IQR increment increase in NO 2 (7.0 μg/m³) and benzene (3.3 μg/m³) was associated with −7.30% (95% CI: −10.98 to −3.46%; p < 0.001) and −6.78% (95% CI: −11.88 to −1.39%; p = 0.015) difference in LTL, respectively. The magnitude of these effects of NO 2 and benzene corresponds to the effect of an increase of 10.3- and 6.0-year in chronological age on LTL. Our study shows that personal exposures to NO 2 and benzene are associated with molecular ageing as indicated by LTL in healthy women residing in the Cape Town region. Image 1 • First ever report on the effects of personal NO 2 and benzene exposure on LTL in a South African population. • Personal NO 2 and benzene exposure was inversely associated with leukocyte telomere length. • The magnitude of the effects corresponds to >6-year increase in chronological age. [ABSTRACT FROM AUTHOR]