Abstract
Accelerated DNA methylation age is linked to all-cause mortality and environmental factors, but studies of associations with socioeconomic position are limited. Researchers generally use small selected samples, and it is unclear how findings obtained with 2 commonly used methods for calculating methylation age (the Horvath method and the Hannum method) translate to general population samples including younger and older adults. Among 1,099 United Kingdom adults aged 28–98 years in 2011–2012, we assessed the relationship of Horvath and Hannum DNA methylation age acceleration with a range of social position measures: current income and employment, education, income and unemployment across a 12-year period, and childhood social class. Accounting for confounders, participants who had been less advantaged in childhood were epigenetically “older” as adults: In comparison with participants who had professional/managerial parents, Hannum age was 1.07 years higher (95% confidence interval: 0.20, 1.94) for participants with parents in semiskilled/unskilled occupations and 1.85 years higher (95% confidence interval: 0.67, 3.02) for those without a working parent at age 14 years. No other robust associations were seen. Results accord with research implicating early life circumstances as critical for DNA methylation age in adulthood. Since methylation age acceleration as measured by the Horvath and Hannum estimators appears strongly linked to chronological age, researchers examining associations with the social environment must take steps to avoid age-related confounding.
Highlights
Accelerated DNA methylation age is linked to all-cause mortality and environmental factors, but studies of associations with socioeconomic position are limited
To investigate the possible contribution of DNAm age acceleration to socioeconomic inequalities in health, we examined the relationship of DNAm age with a range of socioeconomic measures in 1,099 United Kingdom men and women aged 28–98 years
The analytical sample included for DNA methylation analysis (Table 1) was indirectly selected on the basis of age, since DNA methylation was profiled only for persons who had participated as adult survey respondents annually since 1999
Summary
Accelerated DNA methylation age is linked to all-cause mortality and environmental factors, but studies of associations with socioeconomic position are limited. The Horvath clock, based on 8,000 samples encompassing different tissues taken from participants aged ≤100 years of different ethnicities [1] and the Hannum clock, calculated from blood samples of 666 white or Hispanic-American adults [2], obtain linear relationships between chronological age and DNAm age in their samples. It is unclear how well this relationship holds in populations with different age distributions. If the relationship between chronological age and DNAm age is not constant during adulthood, this must be considered in analysis of possible “accelerators” which are age-patterned, to avoid age-related confounding
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