In the Western world, life expectancy rapidly increased in the 20th century, but women still have longer life expectancy than men, and in Finland, 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, reports MedicalXpress.
The difference between the sexes can also be seen in biological ageing, as revealed by a study recently published in The Journals of Gerontology: Series A.
The study investigated whether there are differences in biological ageing 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,” says Anna Kankaanpää, doctoral researcher at the Gerontology Research Centre and the Faculty of Sport and Health Sciences.
More frequent smoking among men explained the sex gap in ageing 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 ageing pace, which was not explained by lifestyle-related factors,” adds Kankaanpää.
“In our study, we also used a quite rare study design and compared ageing 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 oestrogen on health.”
The results help to understand lifestyle behaviours and sex differences related to biological ageing 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 to 42 years) and older (50 to 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.
Study details
Do Epigenetic Clocks Provide Explanations for Sex Differences in Life Span? A Cross-Sectional Twin Study
Anna Kankaanpää, Asko Tolvanen, Pirkko Saikkonen, Aino Heikkinen, Eija Laakkonen, Jaakko Kaprio, Miina Ollikainen, Elina Sillanpää.
Published in The Journals of Gerontology: Series A on 9 November 2022
Abstract
Background
The sex gap in life expectancy has been narrowing in Finland over the past 4–5 decades; however, on average, women still live longer than men. Epigenetic clocks are markers for biological ageing which predict life span. In this study, we examined the mediating role of lifestyle factors on the association between sex and biological ageing in younger and older adults.
Methods
Our sample consists of younger and older twins (21‒42 years, n = 1 477; 50‒76 years, n = 763) including 151 complete younger opposite-sex twin pairs (21‒30 years). Blood-based DNA methylation was used to compute epigenetic age acceleration by 4 epigenetic clocks as a measure of biological ageing. Path modeling was used to study whether the association between sex and biological aging is mediated through lifestyle-related factors, that is, education, body mass index, smoking, alcohol use, and physical activity.
Results
In comparison to women, men were biologically older and, in general, they had unhealthier life habits. The effect of sex on biological ageing was partly mediated by body mass index and, in older twins, by smoking. Sex was directly associated with biological ageing and the association was stronger in older twins.
Conclusions
Previously reported sex differences in life span are also evident in biological ageing. Declining smoking prevalence among men is a plausible explanation for the narrowing of the difference in life expectancy between the sexes. Data generated by the epigenetic clocks may help in estimating the effects of lifestyle and environmental factors on ageing and in predicting aging in future generations.
See more from MedicalBrief archives:
Large study over decades links optimism and prolonged life
Heavy drinking and smoking linked to visible ageing
The Longevity Diet: How nutrition affects ageing and healthy lifespan – US analysis
And why the sex differences in Covid-19 susceptibility?
Good lifestyle choices improve healthy longevity by 7 years
Optimism link to longer life span of women of all races – Harvard study