| Summary: | Telomere length (TL) is an important marker of cellular aging that can be examined from birth to death and provide information about health status and disease risk. TL shortens in early childhood with the majority of the shortening occurring by age 4. TL is associated with stress and obesity in adults. It is possible that exposure to early life stressors and excess adiposity from birth and the first year of life may impact the rate of telomere shortening. Few studies have examined TL in the first years of life, and none of them have examined stress and obesity in infants.We examined TL by qPCR using genomic DNA from dried blood spots in a sample of 109 four-year-old, low-income Latino children and their mothers. TL is expressed as T/S (the ratio of telomeric product vs. single copy gene product). This group of children and their mothers were recruited prenatally in San Francisco at which time socio-demographic and health history was assessed. In addition, child weight and length and maternal body mass index (BMI) have been assessed annually from birth with the child's weight and length measured also at birth and 6 months of age. Maternal depressive symptoms were assessed prenatally, at 4–6 weeks postpartum and annually throughout the follow-up period. Child behavior was evaluated using the child behavior checklist (CBCL) at 3 and 4 years of age for internalizing and externalizing behaviors. Student's t-tests were performed to compare TL in relationship to different childhood exposures – maternal depression, child overweight and obesity, and socio-demographic factors such as child sex, ethnicity, and socioeconomic status. Factors that were significant at p<0.10 were subsequently entered into a multivariate regression model to evaluate independent predictors for shortened TL.In bivariate analysis, being obese at 6 months of age (weight/length ≥ 95th percentile) and being obese at both 6 and 12 months of age were associated with shorter TL at age 4 (1.62±0.36 versus 1.84±0.34, p=0.02 and 1.44±0.30 versus 1.82±0.34, p=0.02, respectively). Exposure to maternal depressive symptoms at age 3 was also associated with shorter TL (1.66±0.25 versus 1.81±0.33, p=0.07). Children of Mexican descent tended to have longer telomeres than those of Central American ancestry (1.85±0.31 versus 1.73±0.38, p<0.07). Exposure to maternal depressive symptoms at other timepoints in early childhood and internalizing or externalizing behavior was not associated with shorter TL. In linear multiple regression analysis, female sex (Coeff = 0.18, 95%CI: 0.04–0.31) as and maternal TL (Coeff = 0.18, 95% CI: 0.04–0.31) predicted longer TL, whereas being obese at 6 and 12 months (Coeff = − 0.49, 95% CI: −0.79 to 0.19) predicted shorter TL.In this population of low-income Latino children, obesity in the first year of life was associated with shorter telomere length at age 4, independent of sex mother's TL and mother's depression. Thus, obesity early in life may shape TL, whereas obesity in the toddler and preschool years may be less associated with obesity at age 4.
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