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This study used accelerometer data from 4,840 US adults to examine how different activity levels affect mortality risk, finding that replacing sedentary time with light or moderate-to-vigorous physical activity was associated with significantly lower mortality rates (18% and 42% respectively) among less active adults, suggesting that even light activity and reduced sitting time can provide important health benefits, particularly for inactive individuals.

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In a 16-year follow-up study of 1,960 healthy Norwegian men aged 40-59, researchers found that higher physical fitness (measured through bicycle ergometer testing) was independently associated with lower mortality risk, with the fittest quartile showing 46% lower all-cause mortality and 59% lower cardiovascular mortality compared to the least fit group, even after adjusting for conventional risk factors.

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In a 46-year follow-up study of 5,107 middle-aged employed Danish men, higher cardiorespiratory fitness (measured by bicycle ergometer testing) was strongly associated with increased longevity - those in the highest fitness category lived 4.9 years longer than those in the lowest category, and each unit increase in VO2max added 45 days to life expectancy, with similar benefits seen for cardiovascular mortality even after accounting for potential reverse causation.

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In a study of 43,356 adults followed for 14.5 years, researchers developed algorithms to estimate cardiorespiratory fitness without exercise testing using routine health metrics (age, BMI, heart rate, etc.). The estimated fitness scores showed similar predictive ability to measured fitness for mortality and cardiovascular events, with each 1-MET increase associated with 10-20% risk reduction, though measured fitness had slightly better discriminative ability.

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We studied physical fitness and risk of all-cause and cause-specific mortality in 10,224 men and 3120 women who were given a preventive medical examination. Physical fitness was measured by a maximal treadmill exercise test. Average follow-up was slightly more than 8 years, for a total of 110,482 person-years of observation. There were 240 deaths in men and 43 deaths in women. Age-adjusted all-cause mortality rates declined across physical fitness quintiles from 64.0 per 10,000 person-years in the least-fit men to 18.6 per 10,000 person-years in the most-fit men (slope, -4.5). Corresponding values for women were 39.5 per 10,000 person-years to 8.5 per 10,000 person-years (slope, -5.5). These trends remained after statistical adjustment for age, smoking habit, cholesterol level, systolic blood pressure, fasting blood glucose level, parental history of coronary heart disease, and follow-up interval. Lower mortality rates in higher fitness categories also were seen for cardiovascular disease and cancer of combined sites. Attributable risk estimates for all-cause mortality indicated that low physical fitness was an important risk factor in both men and women. Higher levels of physical fitness appear to delay all-cause mortality primarily due to lowered rates of cardiovascular disease and cancer.

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In a study of 149,077 participants followed for 8.9 years, prolonged sitting (>8 hours/day) was associated with higher mortality risk, but only among those who were physically inactive (<150 minutes/week of moderate-to-vigorous activity); meeting physical activity guidelines appeared to eliminate the mortality risks of prolonged sitting, and replacing sitting time with vigorous activity showed particularly strong benefits among high sitters (64% lower cardiovascular mortality risk per hour replaced).

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Dataset: NHANES data (1999-2014) analyzing physical activity's impact on mortality in healthy individuals using survey responses and pedometer data (2003-2006 subset), controlling for laboratory-based risk scores.

Results: Higher activity levels showed lower mortality risk (HR 0.91 per MET*hour), while sedentary time increased mortality risk (HR 1.19), with these effects being independent of laboratory risk scores.

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Dataset: Study of 34,212 patients who underwent treadmill stress testing at Henry Ford Health Systems (1991-2009), comparing 7 machine learning models for predicting 10-year mortality using cardiorespiratory fitness data.

Results: Random Forest achieved best performance (AUC=0.97) when using SMOTE sampling, while SVM showed lowest performance; all models improved with SMOTE handling of imbalanced data.

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Physical activity improves health. Different types of activity promote different types of physiologic changes and different health outcomes. A curvilinear reduction in risk occurs for a variety of diseases and conditions across volume of activity, with the steepest gradient at the lowest end of the activity scale. Some activity is better than none, and more is better than some. Even light-intensity activity appears to provide benefit and is preferable to sitting still. When increasing physical activity toward a desired level, small and well-spaced increments will reduce the incidence of adverse events and improve adherence. Prior research on the relationship between activity and health has focused on the value of moderate to vigorous activity on top of an indefinite and shifting baseline. Given emerging evidence that light activities have health benefits and with advances in tools for measuring activities of all intensities, it may be time to shift to zero activity as the conceptual starting point for study.

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Dataset: Cohort study of 2,110 adults followed for 10.8 years examining step volume and intensity's relationship with mortality among middle-aged Black and White adults.

Results: ≥7,000 steps/day associated with 50-70% lower mortality risk vs. <7,000 steps/day; step intensity showed no mortality association.

./static/swissre2020physicalactivity.pdf

Summary article around understanding the effects of physical activity on mortality and morbidity risk. Part 2 of Swiss Re's Big Six Lifestyle Factors.