Today I noticed an open access paper in which the authors examine mortality data for Polish Olympic athletes over the past 90 years or so, and compare it with established historical data for the general population. This blends two topics that are occasionally covered here at Fight Aging!: firstly, the growth in human life expectancy in recent history and its causes, and secondly the topic of how regular exercise and life expectancy interact. It is the present consensus that elite athletes, those at the top of their profession, live longer than the rest of us, but it remains open to debate as to whether this is because more exercise is better, or because very robust people who would have lived longer anyway are more likely to enter the world of professional athletics. Researchers want to map the dose-response curve for exercise, in other words. Even though there is very good, very solid evidence for the benefits of regular moderate exercise versus being sedentary, going beyond that to a more nuanced view of what more or less exercise does for health is a challenging goal given the starting point of statistical snapshots of data from various study populations.
Studying the history of life expectancy isn't much easier, though there the challenges tend to revolve around the ever-decreasing quality of data as you look further back in time. The 20th century marked transitions from hopeful aspiration to solid accomplishment in all fields of medicine, too many profound advances in the capabilities of medical science and practice to list here. As the decades passed, this important progress focused ever more on treatments for age-related conditions. An individual born in the US in 1900 suffered through the end of the era of poor control of infectious disease, prior to modern antibiotics and antiviral drugs, and likely benefited little from later progress towards better control of heart disease and other common age-related diseases. An individual born in the US in 1950, on the other hand, enjoyed a youth with comparatively little fear of disease, and is probably still alive today, with access to far more capable therapies than existed even a couple of decades ago.
Given all of this, one of the interesting things to note in the analysis of the Polish data is that the elite athletes born in the early 20th century appear to have a lower rate of aging than the general population, as determined by a slower rise in mortality over time, but that this difference between athletes and the average individual is greatly diminished for people born in the latter half of the 20th century. This suggests, roughly, that advances in medicine from 1900 to 1950 had a leveling effect, bringing up the average, preventing early deaths, but doing little to address age-related disease. That said, there is a large variation in results across the range of similar studies, both those that look at the history of longevity, and those that look at populations of athletes at a given time. It is wise to consider epidemiological studies in groups rather than one by one, and look for common themes. Still, this one is a fascinating data set for the way in which it combines historical trends and exercise in the study of aging.
A sedentary lifestyle is associated with the onset of chronic diseases including ischaemic heart disease, type-II diabetes and neurodegenerative diseases. Frequent exercise is perceived as a major behavioural determinant for improved life expectancy and a slower rate of ageing. There is little doubt that frequent exercise is beneficial for individuals' well-being, and an active lifestyle reduces the risk for chronic diseases. However, it is still uncertain whether the rate of ageing decelerates in response to frequent and intense physical exercise. Our attempt is the first empirical study to show the application of a parametric frailty survival model to gain insights into the rate of ageing and mortality risk for Olympic athletes.
Our participants for this parametric frailty survival analysis were Polish athletes who had participated in the Olympic Games from 1924 to 2010. We assumed that these athletes were elite in their preferred sports expertise, and that they were engaged in frequent, if not intense, physical exercise. The earliest recorded year of birth was 1875, and the latest was in 1982; total N=2305; male=1828, female=477. For reliable estimates, mortality improvements by calendar events and birth cohort had to be taken into consideration to account for the advancements made in medicine and technology. After the consideration of mortality improvements and the statistical power for parametric survival analysis, we restricted our analysis to male athletes born from 1890 to 1959 (M=1273). For reliable estimates, we preassigned recruited athletes into two categorical cohorts: 1890-1919 (Cohort I); 1920-1959 (Cohort II).
Our findings suggest that Polish elite athletes in Cohort I born from 1890-1919 experienced a slower rate of ageing, and had a lower risk for mortality and a longer life-expectancy than the general population from the same birth cohort. It is very unlikely that these survival benefits were gained within a short observational time. Therefore, we argue that participation in frequent sports from young adulthood reduces mortality risk, increases life-expectancy and slows the rate of ageing. The age-specific mortality trajectories of Cohort I elite athletes also suggest frequent exercise can decelerate the rate of ageing by 1% with an achievement of threefold risk reduction in mortality. In comparison with those of the general population, the differences in energy expenditure, behavioural habits, body mass and sports expertise were likely to be the contributing factors to the higher variance in lifespan among elite athletes.
In Cohort II, the estimated rate of ageing is highly similar between elite athletes and the general population, which contradicts our estimates for Cohort I. This may be attributed to mortality improvements from year 1920 onwards in Poland. These mortality improvements have changed individuals' susceptibilities for different causes of death, which has resulted in an increased variation in lifespan both in the general population and for elite athletes. Interestingly, the comparison of the rate of ageing of elite athletes in Cohort I and II shows a similar rate of ageing. Among the elite athletes, the estimates suggest that Cohort II individuals benefited from a 50% mortality risk reduction as compared with individuals born in Cohort I. The estimated overall mortality risk of the Polish general population is 29% lower in Cohort II than in I.