Men are biologically older than women, study finds

A study at the University of Jyväskylä found that men are biologically older than women. The observed sex difference is partially explained by men's more frequent smoking and larger body size.

In the Western world, life expectancy rapidly increased in the twentieth century, but still women have longer life expectancy than men. In Finland, women live on average five years longer than men. The gap between the sexes was greatest in the 1970s, when life expectancy at birth was almost 10 years higher for women than for men. However, in recent decades, this gap has gradually narrowed. The difference between the sexes can also be seen in biological aging, as a recently published study reveals.

The study investigated whether there are differences in biological aging between men and women and whether the potential differences can be explained by lifestyle-related factors. These differences were investigated in young and older adults.

Several epigenetic clocks were used as measures of biological ageing. Epigenetic clocks enable studying lifespan-related factors during an individual's lifetime. They provide an estimate for biological age in years using DNA methylation levels determined from a blood sample.

We found that men are biologically older than women of the same chronological age, and the difference is considerably larger in older participants."

Anna Kankaanpää, Doctoral Researcher, Gerontology Research Center and the Faculty of Sport and Health Sciences

More frequent smoking among men explained the sex gap in aging in older but not in young adult twins. In addition, men's larger body size explained a small part of the sex gap in both age groups.

"We observed a sex difference in aging pace, which was not explained by lifestyle-related factors," says Kankaanpää.

"In our study, we also used a quite rare study design and compared aging pace among opposite-sex twin pairs. A similar difference was also observed among these pairs of twins. The male sibling was about one year biologically older than his female co-twin. These pairs have grown in the same environment and share half of their genes. The difference may be explained, for example, by sex differences in genetic factors and the beneficial effects of the female sex hormone estrogen on health," Kankaanpää continues.

The results help to understand lifestyle behaviors and sex differences related to biological aging and life expectancy. The results suggest that the decline in smoking among men partly explains why the sex gap in life expectancy has narrowed in recent decades.

The research was carried out in collaboration with the University of Jyväskylä and the University of Helsinki. The subjects were younger (21‒42 years) and older (50‒76 years) adult twins from the Finnish Twin Cohort. Lifestyle-related factors including education, body mass index, smoking, alcohol use and physical activity, were measured using questionnaires.

The AGE-X research project is led by academy researcher Elina Sillanpää. The project was conducted at the Faculty of Sport and Health Sciences, University of Jyväskylä in co-operation with the Institute for Molecular Medicine Finland (FIMM), the University of Helsinki, and the Methodology Center for Human Sciences, University of Jyväskylä. The research has been funded by the Academy of Finland, the EC GenomEUtwin project and the foundations of Sigrid Juselius, Yrjö Jahnsson and Juho Vainio.