Study reveals that meeting physical activity guidelines has a stronger impact on reducing mortality risk with age, while the influence of other health factors diminishes over time.

In a recent study published in JAMA Network Open, researchers pooled over 2 million adults from 4 large cohort studies to examine whether the association between physical activity (PA) and all-cause mortality varies by age.

They found that meeting PA recommendations was consistently associated with lower mortality risk across all ages, with a stronger effect in older adults. In contrast, the benefits of other health factors diminished with age.

PA is strongly linked to a reduced risk of death, but whether this association varies with age remains unclear. While PA levels tend to decrease with age, the risk of death increases, and leading causes of death shift from infectious diseases and injuries in younger adults to noncommunicable diseases like cancer and cardiovascular conditions in older adults.

Despite these differences, current PA guidelines recommend the same levels of activity for all adults: 150–300 minutes of moderate-intensity or 75–150 minutes of vigorous-intensity PA weekly, though even lower amounts provide benefits.

Given the physiological and mortality risk changes across age groups, understanding how PA impacts mortality at different ages is critical. This could help refine age-specific PA recommendations to maximize health benefits throughout adult life.

Therefore, in the present study, researchers analyzed data from multiple large cohorts to investigate how the associations between physical activity, other health factors, and mortality potentially change with age.

Researchers pooled data from four large cohorts (National Health Interview Survey, United Kingdom Biobank, China Kadoorie Biobank, and Mei Jau) with 2,011,186 participants aged 20–97 years. The mean age of participants was 49.1 years, and 55% were women. Participants self-reported leisure-time PA, which was measured in metabolic equivalents [MET]-hours per week, and their PA levels were categorized as meeting or not meeting PA guidelines. Mortality data were obtained through linkage to national death registries, with a median follow-up period of 11.5 years.

Covariates such as education, smoking, alcohol use, body weight, diabetes, and hypertension were harmonized for consistency. PA and these health factors were analyzed to assess their associations with all-cause mortality across different age groups. The study aimed to understand how the benefits of meeting PA guidelines and the influence of other health factors on mortality vary by age. Statistical analysis involved the use of Cox proportional hazards regression, restricted cubic splines, likelihood ratio tests, odds ratios, stratified cohort-specific models, and sensitivity analyses.

According to the study, a total of 177,436 deaths (8.8%) occurred during the study period. The study found a nonlinear dose-response relationship between PA and all-cause mortality, with greater reductions in mortality risk observed at higher PA levels. Meeting the recommended 7.5 MET-hours per week of PA was associated with a 14% lower mortality risk while engaging in up to four to five times the recommended level (22.5 – 30 MET-hours per week) provided the largest risk reduction (26%). Even half the recommended PA level (3.75 MET-hours per week) was associated with an 8% all-cause mortality risk reduction.

Age was found to modify this association, with older adults benefiting more significantly from higher PA levels than younger adults. Adhering to PA guidelines was associated with a 22% reduction in mortality risk in the total sample, with the effect becoming more pronounced with increasing age. Other modifiable health factors, including education, nonsmoking, healthy weight, and absence of hypertension or diabetes, were also associated with lower mortality risk, but these associations were observed to diminish with age. Sensitivity analyses confirmed the robustness of the findings.

The study is strengthened by its large sample size, multinational cohorts, detailed harmonization of data, and robust sensitivity analyses confirming consistent findings across diverse subgroups and contexts. However, the study is limited by self-reported data for PA and modifiable health factors, a single time-point assessment of PA, the inability to assess all PA domains or modes, and potential biases such as recall bias, reverse causation, and residual confounding, restricting causal inference.

In conclusion, the study found that PA consistently reduces mortality risk across all adult age groups, unlike other modifiable health factors (education, smoking, alcohol, weight, hypertension, and diabetes), whose impact lessens with age. The findings emphasize the importance of promoting regular PA throughout life.