The Finnish Twin Cohort's Odd Results for the Effects of Exercise on Mortality

You might recall that the Horvath epigenetic clock did not exhibit differences in biological age when comparing twins, given one twin that is sedentary versus one twin that is active. I blamed that on the epigenetic clock at the time, and it is certainly true that these clocks do exhibit quirks. The results noted here exonerate the Horvath clock and focus instead on the study population itself, however. The observed long-term relationship between exercise and mortality in this group is not what one would expect given the dose-response curve for exercise that has been established by many other, larger epidemiological studies.

Researchers investigated the links between long-term leisure-time physical activity and mortality, as well as whether physical activity can mitigate the increased risk of mortality due to genetic predisposition to diseases. Moreover, they examined the relationship between physical activity and later biological aging. The study included 22,750 Finnish twins born before 1958 whose leisure-time physical activity was assessed in 1975, 1981 and 1990. Mortality follow-up continued until the end of 2020.

Four distinct sub-groups were identified from the data, which was based on leisure-time physical activity over the 15-year follow-up: sedentary, moderately active, active and highly active groups. When the differences in mortality between the groups were examined at the 30-year follow-up, it was found that the greatest benefit - a 7% lower risk of mortality - was achieved between the sedentary and moderately active groups. A higher level of physical activity brought no additional benefit. When mortality was examined separately in the short and long term, a clear association was found in the short-term: the higher the level of physical activity, the lower the mortality risk. In the long term, however, those who were highly active did not differ from those who were sedentary in terms of mortality.

The researchers also investigated whether following the World Health Organization's physical activity guidelines affects mortality and genetic disease risk. The guidelines suggest 150 to 300 minutes of moderate or 75 to 150 minutes of vigorous activity weekly. The study found that meeting these guidelines did not lower mortality risk or alter genetic disease risk. Even for twins who met the recommended levels of PA over a 15-year period, no statistically significant difference in mortality rates was found compared to their less active twin pair.

Link: https://www.jyu.fi/en/news/does-exercise-really-extend-life-finnish-twin-study-offers-new-insights

Comments

I interpret the study to say that although they may have initially divided the cohorts into 4 distinct activity levels, that they didn't have enough participants to get statistical significance using 4 groups, so they did the statistical analysis based on a regrouping into 2 groups (those that meet the PA guidelines and those that did not meet the guidelines).

Posted by: JohnD at March 21st, 2025 12:36 PM

This is the result you'd expect if exercise did almost nothing for you and most results you see in the literature were due to reverse causality (ie you stop exercising/exercise less when your health deteriorates).

Posted by: ale at March 21st, 2025 6:08 PM
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