A Meta-Analysis of the Ability of Exercise to Reduce Age-Related Mortality

Exercise improves health, and that statement continues to be the case throughout life, even into late old age, and while suffering from age-related conditions that impact the ability to exercise. Exercise exhibits a dose-response curve, just like any other intervention to improve health. More is better for near all people: one has to undertake a great deal of physical activity indeed to come to the point of diminishing returns or self harm. One of the interesting findings of the past twenty years, achieved after it became cost-effective to measure activity more precisely via the use of wearable accelerometers, is that even very modest levels of exercise make a sizable difference to mortality rates in older people. Becoming sedentary is a fate to be avoided.

The current evidence for the general population regarding physical activity and mortality is comprehensive and unambiguous. Numerous large cohort studies have consistently demonstrated an inverse relationship between physical activity levels and mortality. Compared with the lower physical activity groups, the risk of premature death was remarkably reduced in the higher physical activity groups. One meta-analysis revealed that per 1 hour increment of moderate-intensity physical activity per week, the relative risk of mortality was reduced by 4%.

In the updated physical activity guidelines for healthy adults from the U.S. Department of Health and Human Services, a clear dose-response association between the volume of physical activity and mortality rates has been shown. The shape of the dose-response curve is characterized by a regressive, non-linear effect, where the greatest difference in mortality rates occurs among inactive and minimally active individuals. For higher physical activity levels, the dose-response curve flattens out. This means that the relative risk of mortality continues to decline with higher volumes of physical activity with no adverse effects on mortality, even at very high levels of physical activity.

The objective of this study was to conduct a systematic review and dose-response meta-analysis of physical activity and mortality in people with selected non-communicable diseases (NCDs). We aimed to define the dose-response relationship between post-diagnosis physical activity and mortality rates for nine NCDs with a high global burden of disease, including low back pain, type 2 diabetes (T2D), osteoarthritis, depressive disorder, chronic obstructive pulmonary disease (COPD), breast cancer, lung cancer, stroke, and ischemic heart disease (IHD).

In total, 28 studies were included in the meta-analysis: 12 for breast cancer, 6 for type 2 diabetes, 8 for ischemic heart disease and 2 for COPD. The linear meta-analysis revealed that each 10 metabolic equivalent task hours increase of physical activity per week was associated with a 22% lower mortality rate in breast cancer patients, 12% in ischemic heart disease patients, 30% in COPD patients, and 4% in type 2 diabetes patients. There was indication of a non-linear association with mortality risk reductions even for low levels of activity, as well as a flattening of the curve at higher levels of activity. Thus higher levels of post-diagnosis physical activity are associated with lower mortality rates in breast cancer, type 2 diabetes, ischemic heart disease, and COPD patients, with indication of a no-threshold and non-linear dose-response pattern.

Link: https://doi.org/10.1186/s12966-020-01007-5

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