Increased activity in middle age and beyond may decrease the risk for death from all causes, cardiovascular disease (CVD), and cancer, according to a study published online on June 26 in BMJ.
Middle-aged study participants benefited from increased physical activity regardless of past activity levels, history of CVD or cancer, and changes in established risk factors, such as overall diet quality, body weight, blood pressure, and triglyceride and cholesterol levels.
The findings suggest that engaging in at least 150 minutes of moderate-intensity physical activity per week, as recommended by the World Health Organization (WHO), could prevent almost half of deaths linked to physical inactivity.
"These results are encouraging, not least for middle aged and older adults with cardiovascular disease and cancer, who can still gain substantial longevity benefits by becoming more active, lending further support to the broad public health benefits of physical activity," write author Alexander Mok, a PhD candidate at the University of Cambridge, United Kingdom, and colleagues with the European Prospective Investigation Into Cancer and Nutrition–Norfolk (EPIC-Norfolk) study.
"In addition to shifting the population towards meeting the minimum physical activity recommendations, public health efforts should also focus on the maintenance of physical activity levels, specifically preventing declines over mid to late life," they add.
Past research has suggested that being physically active may lower the risk for death from a variety of causes, including CVD and cancer. But most studies — over 90% from 1975 to 2016 — have evaluated physical activity at a single time point. Relatively little is known about the long-term effects of physical activity on mortality risk. Even less is known about the long-term effects of changes in physical activity and other lifestyle factors, such as diet and weight.
The researchers conducted a population-based cohort study that included 14,599 women and men from the larger EPIC-Norfolk study, a prospective study of 25,639 women and men aged 40 to 79 years who live in Norfolk, United Kingdom, and were recruited from community general practices from 1993 to 1997.
At baseline, the mean age of included participants was 58 years; 56.6% were women. Participants attended a baseline clinic visit and underwent three follow-up assessments. The first consisted of answering a validated questionnaire about occupational and leisure activity as well as other risk factors for death. It was mailed 1.7 years after baseline. The second was a clinic visit 3.6 years after baseline, and the third involved answering a similar questionnaire that was mailed 7.6 years after baseline.
Researchers estimated physical activity expenditure (PAEE) as energy expended per kg per day using an equation that had been independently validated through use of movement and heart rate monitoring data.
Information on diet came from a validated food frequency questionnaire. Researchers calculated an overall diet quality score that took into account diet components known to affect health, such as sodium, vegetables, and sugar-sweetened beverages.
To decrease risk for bias from underlying health conditions, participants who died within 1 year of the last assessment were excluded from analyses.
Participants were followed to 2016. The median follow-up was 12.5 years after the last assessment.
During the study, 3148 participants died, 950 from CVD and 1091 from cancer. During this time, mean PAEE declined by 17%.
The results were controlled for baseline activity levels, age, sex, smoking, alcohol use, education, social class, overall diet quality, body weight, medical history, and other risk factors, such as blood pressure and cholesterol level. The findings suggest that higher activity levels and long-term increases in activity were linked to lower risk for death.
Each 1 kJ/kg/day per year increase in physical activity was linked to a 24% decrease in risk for all-cause mortality (hazard ratio [HR], 0.76; 95% confidence interval [CI], 0.71 – 0.82), a 29% decrease in risk for CVD death (HR, 0.71; 95% CI, 0.62 – 0.82), and an 11% decrease in risk for cancer death (HR, 0.89; 95% CI, 0.79 – 0.99).
Such an increase is about the same as a gradual increase over 5 years from baseline inactivity to the WHO-recommended minimum requirements of 150 min/week of moderate-intensity physical activity.
Results were similar for persons who had a history of CVD and cancer.
Further analyses suggested that individuals who increased their activity levels over time had lower risk for death compared with those who remained inactive. Those with higher activity levels benefited most.
For example, compared with those who remained inactive, becoming more active was linked to 24% lower risk for all-cause death among those with low baseline activity levels (HR, 0.76; 95% CI, 0.65 — 0.88).
Compared with consistently inactive participants, those with medium baseline activity levels who increased their activity had 38% lower risk for death (HR, 0.62; 95% CI, 0.53 — 0.72), and those with high baseline levels had 42% lower risk for death (HR, 0.58; 95% CI, 0.43 — 0.78).
Population-levels estimates suggested that meeting and maintaining at least the minimum WHO-recommended physical activity levels (5 kJ/kg/day) would prevent 46% of deaths associated with physical inactivity. Individuals with medium levels of increase in activity and those who maintained medium levels may reap the greatest benefits, with 25% and 21% of deaths prevented, respectively. For those who increase their activity at a high level, 21% of deaths could potentially be prevented.
The authors mention that it was surprising that the results suggested that an increase in activity yielded benefits regardless of established cardiometabolic risk factors. Because other studies have suggested that these variables may weaken the link between activity and decreased death, further study is needed on this issue.
The study has several limitations. Because it is an observational study, results do not prove that increased activity levels in middle age cause decreased risk for death. Also, the analysis included people who completed follow-up almost a decade after they entered the study, so results may not be generalizable to a broader population.
Because the results are of broad public interest, the authors plan to make the results available to the general public via websites, participant engagement events, seminars, and conferences.
The study was funded by grants from the Medical Research Council, Cancer Research UK, the Stroke Association, the British Heart Foundation, the Department of Health, the Food Standards Agency, the Wellcome Trust, the National Science Scholarship from Singapore, and A*STAR (the Agency for Science, Technology and Research). The authors have disclosed no relevant financial relationships.
BMJ. Published online June 26 2019. Full text
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