By Ellen Feldman, MD
Altru Health System, Grand Forks, ND
Summary Points
- Data from 4,840 adults using accelerometers to track exercise intensity over one week was used to compare quantity of moderate-to-vigorous physical activity (MVPA) to mortality rate of the group over the following nine to 12 years.
- Adjusting for multiple variables and using advanced statistical techniques, results indicated that increasing MVPA by 10 minutes daily was associated with a 6.9% decrease in deaths/year, 20 minutes daily was associated with a 13.0% decrease in deaths/year, and 30 minutes daily was associated with a 16.9% decrease in deaths/year.
- Looking at results from a different perspective, adjusting for multiple variables, results indicate that increasing MVPA by 10 minutes daily results in an estimated 111,174 fewer deaths/year, 20 minutes daily results in estimated 209,459 fewer deaths/year, and 30 minutes daily results in an estimated 272,297 fewer deaths/year in the United States.
SYNOPSIS: This large cohort study using objective measurement of exercise intensity approximates that potentially 110,000 U.S. deaths/year can be prevented by a 10-minute daily increase in moderate-to-vigorous physical activity in adults ages 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 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
With a goal of estimating the health effect of increased physical activity 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 physical activity. Data from the National Health and Nutrition Examination Survey (NHANES) met these needs. This Centers for Disease Control and Prevention (CDC) survey beginning in the 1960s and evolving 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 a seven-day period. 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
Saint-Maurice et al used responses of 4,840 of the 6,355 adults aged 40-85 years with accelerometer results, excluding participants who, for a variety of reasons (including device failure), did not have sufficient data for this study. Eight physical activity categories based on minutes of moderate-to-vigorous physical activity (MVPA) were created, with a baseline of 0-19 minutes daily and > 140 minutes daily as the maximum. In order 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 towards determining an estimation of the number of deaths per year avoided by increasing physical activity. 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.
Results
Mean follow-up time was 10.1 years; 1,165 of the 4,840 participants died during this period. Hazard ratios (adjusted for multi-variables) for death dropped from 0.69 to 0.28 across the eight physical activity categories as shown in Table 1.
Table 1. Hazard Ratios for Death Across MVPA Levels as Measured by One Week of Accelerometer Data
|
|
Number of Respondents (%)
|
Hazard Ratio
|
Number (%) of Study Group Needing Assistive Equipment for Mobility
|
|
0-19 minutes MVPA
|
548 (7.9%)
|
1.00 (reference)
|
280 (49.4%)
|
|
20-39 minutes MVPA
|
616 (10%)
|
0.69 (95% CI, 0.55-0.85)
|
164 (26.3%)
|
|
40-59 minutes MVPA
|
635 (11.8%)
|
0.51 (95% CI, 0.42-0.63)
|
94 (12.4%)
|
|
60-79 minutes MVPA
|
614 (12.7%)
|
0.40 (95% CI, 0.29-0.55)
|
66 (9.5%)
|
|
80-99 minutes MVPA
|
633 (14.4%)
|
0.34 (95% CI, 0.25-0.47)
|
42 (5.1%)
|
|
100-119 minutes MVPA
|
508 (12.1%)
|
0.32 (95% CI, 0.21-0.48)
|
31(4.7%)
|
|
120-139 minutes MVPA
|
384 (9.3%)
|
0.30 (95% CI, 0.19-0.48)
|
20 (2.9%)
|
|
> 140 minutes MVPA
|
902 (21.7%)
|
0.28 (95% CI, 0.18-0.42)
|
35 (2.7%)
|
|
MVPA: moderate-to-vigorous physical activity; CI: confidence interval
|
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. (See Table 2.)
Table 2. Effect of Increasing MVPA on Deaths Yearly and Estimated Effect at Population Level
|
|
Adding 10 Minutes MVPA Daily
|
Adding 20 Minutes MVPA Daily
|
Adding 30 Minutes MVPA Daily
|
|
Deaths/year (national database)
|
6.9% decrease
|
13.0% decrease
|
16.9% decrease
|
|
Estimated preventable deaths/year (population level)
|
111,174
(95% CI, 79,594-142,754)
|
209,459
(95% CI, 146,299-272,619)
|
272,297
(95% CI, 177,557-367,037)
|
|
MVPA: moderate-to-vigorous physical activity; CI: confidence interval
|
COMMENTARY
This prospective cohort study showed an association between a modest increase in MVPA among individuals 40-85 years od age with the prevention of an estimated 110,000 deaths/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 whether the activity levels and intensity from the monitored week reflect ongoing activity patterns.
In addition, there was no control (such as a sham week) for the effect on activity level and intensity of just wearing an accelerometer. Nevertheless, the use of accelerometer data provides valuable objective information regarding intensity of physical activity.
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 physical activity (such as gardening or biking on level terrain at speeds < 10 miles/hour). During vigorous intensity activity, it should be difficult to say more than a few words without stopping to catch a breath (such as jumping rope or hiking uphill).6
Saint-Maurice et al conclude with the statement (emphasis added), “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 physical activity for adults was addressed in a recent Journal of the American Medical Association (February 2022) issue. Nakamura et al presented a cohort study looking at the association between aging satisfaction and health and noted that an individual’s beliefs about aging (aging satisfaction) is associated with improvement in some health behaviors, including engaging in more physical activity.7 An editorial in this same issue addressed structural ageism and the effect of societal beliefs and policies on individual and population health. Specifically, in this editorial, Dr. Levy noted that older persons who experience age discrimination (on multiple levels) are less likely to engage in physical activity.8
A focus on the distribution of respondents among the eight accelerometer groups provided some encouraging news in this regard (see Table 1), 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 physical activity. 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. Updated March 31, 2022. https://www.cdc.gov/nchs/nhanes/index.htm
- Medical Research Council. Accelerometers. https://dapa-toolkit.mrc.ac.uk/physical-activity/objective-methods/accelerometers
- Centers for Disease Control and Prevention. Measuring physical activity intensity. Updated Sept. 17, 2020. https://www.cdc.gov/physicalactivity/basics/measuring/index.html
- 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.
