By Ellen Feldman, MD
Altru Health System, Grand Forks, ND
SYNOPSIS: Using objective measurements of exercise intensity, researchers approximated 110,000 U.S. deaths/year could be prevented by a 10-minute daily increase in moderate-to-vigorous physical activity in adults age 40-85 years.
SOURCE: Saint-Maurice PF, Graubard BI, Troiano RP, et al. Estimated number of deaths prevented through increased physical activity among U.S. adults. JAMA Intern Med 2022;182:349-352.
Increasingly, studies have pointed to an association between physical activity (PA) and longevity.1,2 However, many of these investigations are hampered by factors such as self-report of activity level and intensity, small number of participants, or nonrandomized samples, leading to “dosage recommendations” and other specifics of this intervention that are difficult to generalize.1-3
To estimate the health effect of more PA at a population level, Saint-Maurice et al cited the need for a large, population-based pool of respondents and an objective tool to measure PA. Data from the National Health and Nutrition Examination Survey (NHANES) met these needs. This CDC survey, which began in the 1960s and has evolved over time, has remained true to the mission of monitoring the “health and nutritional status” of U.S. children and adults. Typically, NHANES combines interviews and periodic on-site examinations and uses 5,000 nationally representative respondents across the country each year.4 From 2003 to 2006, NHANES asked respondents to wear an accelerometer for seven days. Notably, accelerometers differ from other devices that collect movement-based data, such as pedometers, in that accelerometers measure a change in velocity of an object over time and, thus, allow inference of intensity of action.5 Researchers used responses of 4,840 of the 6,355 adults age 40-85 years with accelerometer results, excluding participants who, for a variety of reasons (including device failure), did not produce sufficient data for this study. The authors created eight PA categories based on minutes of moderate-to-vigorous PA (MVPA), with a baseline of 0-19 minutes daily and > 140 minutes daily as the maximum. To determine longevity of the participants, mortality follow-up until the end of 2015 was monitored via a national death database.
Statistical analysis of the data was pointed toward determining an estimation of the number of deaths per year prevented by increasing PA. Included in the process was adjustment for confounding factors, such as age, sex, race and ethnicity, education level, body mass index, diet, substance use (e.g., smoking, alcohol), and general health. Mean follow-up time was 10.1 years; 1,165 of the 4,840 participants died during this period. Hazard ratios (adjusted for variables) for death dropped from 0.69 to 0.28 across the eight PA categories, from highest to lowest. An additional statistical analysis showed increasing MVPA by 10 minutes daily was associated with a corresponding decrease in number of deaths yearly. An estimated effect of increasing MVPA at population level reflects an increasing number of preventable deaths with each 10-minute raise in MVPA.
COMMENTARY
The authors showed an association between a modest increase in MVPA among individuals age 40-85 years with the prevention of an estimated 110,000 deaths per year in the United States, and an increasing effect with further raises in MVPA. Perhaps the most glaring limitation of this study is the reliance on a single week of unblinded accelerometer data. There is no evidence indicating whether the activity levels and intensity from the monitored week reflect ongoing activity patterns. In addition, there was no control (e.g., a sham week) for the effect on activity level and intensity of just wearing an accelerometer. Nevertheless, using accelerometer data provided valuable objective information regarding intensity of PA.
There is clinical relevance when MVPA is translated into practical terms, usable by patients. According to the CDC, an individual should be able to talk but not sing while engaging in moderate PA (such as gardening or biking on level terrain at speeds slower than 10 miles/hour). During vigorous intensity activity, it should be difficult to say more than a few words without stopping to catch a breath (e.g., jumping rope or hiking uphill).6 Saint-Maurice et al concluded with the statement, “These findings support implementing evidence-based strategies to improve physical activity for adults and potentially reduce deaths in the U.S.” As death is inevitable for all individuals, this statement may be more accurately phrased as either a reduction in death rate or an increase in lifespan (rather than “reduce deaths”).
Coincidentally, the issue of improving PA for adults was addressed in another recently published paper. Nakamura et al presented a cohort study of the association between aging satisfaction and health. They noted an individual’s beliefs about aging satisfaction is associated with improvement in some health behaviors, including engaging in more PA.7 The author of an accompanying editorial addressed structural ageism and the effect of societal beliefs and policies on individual and population health. Specifically, the author noted older patients who experience age discrimination (on multiple levels) are less likely to engage in PA.8 A focus on the distribution of respondents among the eight accelerometer groups provided some encouraging news in this regard, since slightly more than 20% of the total group participants fell into the highest MVPA category. The smallest percentage of respondents in any one category was 7.9%; these individuals fell into the lowest MVPA category at 0-19 minutes of MVPA.
The primary care provider is well-positioned to use findings from the Saint-Maurice et al cohort study. The results point to increased longevity associated with 10- to 30-minute incremental increases in MVPA. This strengthens the argument to encourage patients to implement more PA. The guidelines from the CDC regarding MVPA may be used to assist patients to self-assess the intensity of exercise and adjust accordingly.
REFERENCES
- Carlson SA, Adams EK, Yang Z, et al. Percentage of deaths associated with inadequate physical activity in the United States. Prev Chronic Dis 2018;15:E38.
- Zhao G, Li C, Ford ES, et al. Leisure-time aerobic physical activity, muscle-strengthening activity and mortality risks among US adults: The NHANES linked mortality study. Br J Sports Med 2014;48:244-249.
- Love R, Adams J, van Sluijs, et al. A cumulative meta-analysis of the effects of individual physical activity interventions targeting healthy adults. Obes Rev 2018;19:1164-1172.
- Centers for Disease Control and Prevention. National health and nutrition examination survey. Page last reviewed April 28, 2022.
- Medical Research Council. Accelerometers.
- Centers for Disease Control and Prevention. Measuring physical activity intensity. Updated Sept. 17, 2020.
- Nakamura JS, Hong JH, Smith J, et al. Associations between satisfaction with aging and health and well-being outcomes among older U.S. adults. JAMA Netw Open 2022;5:e2147797.
- Levy BR. The role of structural ageism in age beliefs and health of older persons. JAMA Netw Open 2022;5:e2147802.
Using objective measurements of exercise intensity, researchers approximated 110,000 U.S. deaths/year could be prevented by a 10-minute daily increase in moderate-to-vigorous physical activity in adults age 40-85 years.
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