Spending More Leisure Time Physically Active Can Add Years to Your Life
Abstract & Commentary
By Dónal P. O’Mathúna, PhD, Senior Lecturer in Ethics, Decision-Making & Evidence, School of Nursing and Human Sciences, Dublin City University, Ireland. Dr. O’Mathúna reports no financial relationships relevant to this field of study.
Synopsis: A pooled analysis of data from six prospective cohort studies found that more leisure time physical activity was associated with a reduced risk of mortality and increased life expectancy beyond age 40. Associations were found at all levels of body mass index. Subgroup analyses identified greater increases in life expectancy for blacks than whites, for former smokers than current smokers or those who never smoked, and for those with a history of cancer or heart disease.
Source: Moore SC, et al. Leisure time physical activity of moderate to vigorous intensity and mortality: A large pooled cohort analysis. PLoS Med 2012;9:e1001335; Epub 2012 Nov 6.
The association between physical activity and risk of mortality is well established. Numerous epidemiological studies show that physical activity reduces the risk of mortality by about 30%. One specific study found strong evidence that physical activity in adults reduces the risk of coronary heart disease, high blood pressure, stroke, type 2 diabetes, breast and colon cancers, depression, and falling.1 More specifically, between 6-10% of the worldwide disease burden for each of these diseases is due to physical inactivity. However, few studies have quantified the number of years gained with different levels of physical activity or examined how this is impacted by body mass index (BMI). Also, little is known about the impact of variables like race, smoking history, and cancer or heart disease on the association between activity and longevity. This study focused on the impact of physical activity on longevity for people older than age 40 years.
To explore these factors, the authors examined data from six prospective cohort studies that are part of the National Cancer Institute Cohort Consortium. Five were conducted in the United States and one in Sweden. Each study included members of the general population with a focus on risk factors for different diseases. To be eligible, studies had to have a prospective design, at least 5 years’ follow-up, at least 1000 deaths among non-Hispanic white participants, and assessment of height, weight, smoking status, and time spent in leisure time physical activity. The combined study population was 56% female and 96.4% white, and the median age at baseline was 61 years (range, 21-98).
The primary exposure was leisure time physical activity of either moderate or vigorous intensity. Leisure time physical activities are activities that people voluntarily engage in and that are not required for a job, housework, transportation, or other essentials of daily living. They include sports, exercising, gardening, and recreational walking. Moderate-intensity activities require moderate effort and noticeably increase the heart rate. They include brisk walking and gardening. Vigorous activity requires a large effort, and leads to rapid breathing and a substantial increase in heart rate. This includes running, cycling, and fast swimming. Participants self-reported the time spent weekly engaged in moderate and vigorous leisure time exercise.
Complete data on physical activity, BMI, and mortality risk existed for 632,091 people aged 40 years or older and who were not underweight. Among those 40 and older, 80,767 deaths occurred during a median 10-year period. Physical activity was calculated in units of metabolic equivalent hours per week (MET-h/wk). Five MET-h/wk is equivalent to about 100 minutes of brisk walking per week.
Groups were defined as those with no leisure activity, low levels of leisure activity (up to 3.74 MET-h/wk or 75 minutes brisk walking per week), and the minimum recommended physical activity level (7.5 MET-h/wk or 150 minutes brisk walking per week). With each group comparison, higher levels of moderate to vigorous leisure activity were associated with lower risk of mortality and longer life expectancy after 40. Compared with no leisure activity, low levels and minimum recommended levels increased life expectancy by 1.8 and 2.5 years, respectively (95% confidence interval [CI] 1.6-2.0 and 2.2-2.7, respectively). Those at or slightly above the minimum recommended levels increased life expectantly by 3.4 years (95% CI 3.2-3.6). Those at two or three times the minimum level had longer life expectancy of 4.2 and 4.5 years, respectively (95% CI 4.0-4.5 and 4.3-4.7, respectively). The greatest gains occurred at 15 MET-h/wk or about 300 min brisk walking per week.
When BMI was added to the analyses, low physical activity was associated with lower life expectancy and higher risk of death in all BMI groups. For example, for those with normal weight (BMI 18.5-24.9 kg/m2), those with no leisure activity had 4.7 fewer years of life than those meeting the minimum recommended levels. For those in the overweight category (BMI 25.0-29.9 kg/m2), it was 3.9 fewer years; those in obese class I (BMI 30.0-34.9 kg/m2), 3.4 fewer years; and those in obese class II+ (BMI ≥ 35.0 kg/m2), 2.7 fewer years. In each physical activity group, being obese (but not being overweight) was associated with shorter life expectancy.
The large number of pooled participants allowed a number of subgroup analyses to be performed. These found little difference according to gender, but stronger associations for black individuals, former smokers, and those with a history of cancer or heart disease. For example, for those meeting the minimum recommended leisure activity levels compared to those with no leisure activity, the years of life gained after 40 were 3.4 for whites, and 5.3 for blacks; years gained were 4.1 for former smokers, 3.0 for those who never smoked, and 2.6 for current smokers; years gained were 5.3 for cancer survivors, 4.3 for those with heart disease, and 2.8 for those with neither. Association with education was complex, possibly confounded by socioeconomic factors that were not a focus of this study. At all activity levels, those with some college or post-high school training had greater gains in life expectancy than college graduates or those with no more than high school education (the latter two groups being about equivalent).
In every category, adding even low amounts of leisure time physical activity was associated with increased longevity. The authors concluded, “This finding may help convince currently inactive persons that a modest physical activity program is ‘worth it’ for health benefits, even if it may not result in weight control.”
This study provides additional and more robust evidence to support public health efforts to increase people’s activity levels. By pooling data from a number of large studies, this analysis supports the findings of earlier, smaller studies. One of the intriguing comparisons was that being inactive and in obese class II+ (BMI ≥ 35.0 kg/m2) is associated with 7.2 years of life lost, while long-term cigarette smoking reduces life expectancy by about 10 years.
This study lends support to 2008 Physical Activity Guidelines Advisory Committee recommendations of 150 minutes per week of moderate intensity activity, or 75 min/wk of vigorous activity for adults aged 18-64 years.2 The guidelines noted additional benefits would be achieved by 300 min/wk of moderate or 150 min/wk of vigorous activity. These were based on an estimated 20% reduced risk of mortality with the minimum recommended activity and 39% risk reduction with the higher levels. The guidelines cautioned that larger studies were needed to confirm these findings, which the current study provides. This study found equivalent risk reductions of 19% and 41% with much larger numbers of participants. Similar results have been found in other North American and European studies, and also recently with a Taiwanese study, suggesting these benefits may be transcultural.3 The World Health Organization has adopted the same guidelines and makes these available in a number of languages.4
The main limitation with the current study is the reliance on self-reported data. Errors in recalling activity amounts and intensities, as well as body weight, may have impacted the findings. In addition, the focus on moderate-to-vigorous intensity activities may have missed the contribution of less-intense activities. Although statistical methods were used to account for heterogeneity in pooling the six studies, it is possible that unaccounted differences may have influenced the findings. A limitation in generalizing the results is the preponderance of white adults, with only 3% black and 1% other. This reflects the recruitment strategies in the original six studies.
Even with these limitations, this study provides further evidence of the importance and beneficial contribution of physical activities to health. It provides evidence of benefit in outcomes to which people can easily relate — years of life lost or gained. In addition, it provides evidence that particular groups of people, such as blacks, former smokers, and those with a history of cancer or heart disease, may experience additional benefit from engaging in moderate to vigorous leisure time physical activities. These findings can provide confidence in making recommendations to almost everyone to find leisure time activities they enjoy.
1. Lee I-M, et al. Effect of physical inactivity on major noncommunicable diseases worldwide: An analysis of burden of disease and life expectancy. Lancet 2012;380:219-229.
2. U.S. Department of Health & Human Services. 2008 Physical Activity Guidelines for Americans. 2008. Available at: www.health.gov/paguidelines/. Accessed Dec. 10, 2012.
3. Wen CP, et al. Minimum amount of physical activity for reduced mortality and extended life expectancy: A prospective cohort study. Lancet 2011;378:1244-1253.
4. World Health Organization. Global Recommendations on Physical Activity for Health. 2010. Available at: www.who.int/dietphysicalactivity/factsheet_recommendations/en/. Accessed Dec. 10, 2012.