By Traci Pantuso, MD
Adjunct Faculty, Research Investigator, Bastyr University, Seattle
SYNOPSIS: In a prospective cohort study of older U.S. adults, replacing sedentary behavior with physical activity was associated with a lower cancer mortality risk.
SOURCE: Gilchrist SC, Howard VJ, Akinyemiju T, et al. Association of sedentary behavior with cancer mortality in middle-aged and older U.S. adults. JAMA Oncol 2020;6:1210-1217.
Cancer is the second leading cause of death in U.S. adults.1 Physical activity is associated with reductions in both the risk of incident cancer and the risk of death from cancer.2,3 There is conflicting evidence regarding the relationship between physical activity and cancer mortality.3,4 Most studies of that relationship have relied on self-reported physical activity measurements, which are known to contain reporting bias and measurement error.4-6
To further understand the effects of physical activity and cancer mortality, Gilchrist et al investigated the relationship between physical activity measured with an accelerometer (wearable device) and cancer mortality in participants of the Reasons for Geographic and Racial Differences in Stroke (REGARDS) Study.7 The REGARDS Study includes 30,239 Black and white U.S. adults age 45 years or older, recruited between 2003 and 2007 from across the contiguous states. During study enrollment, participant cardiovascular disease risk factor data and demographic information were collected through a phone interview, and an in-home physical assessment was conducted. Physical activity was measured using the Actical accelerometer that participants wore on a nylon belt over their right hip. Participants were instructed to wear the device for seven consecutive days during waking hours. The Actical accelerometer used in this study is validated for the measurement of physical activity and sedentary behavior.
Participants from the REGARDS Study were included if they had accelerometer data from active REGARDS participants from May 12, 2009, to Dec. 31, 2012. Participants undergoing active cancer treatment were excluded from this study. In total, 8,002 participants were included in the data analysis because each one had adherent accelerometer wear and had follow-up data for mortality.
The data analysis was performed from April 18, 2019, to April 21, 2020. Accelerometer wear was defined as wearing the accelerometer greater or equal to 10 hours for four days or more. Cancer mortality was identified through a variety of ways, including at the biannual follow-up appointments, Social Security Death Index, the National Death Index, and death information from participants’ proxies. Time to death was identified based on death certificates, Social Security Death Index and National Death Index data, and the final cause of death was defined after adjudication by REGARDS clinical investigators. Cancer deaths through Dec. 31, 2016, were included in this study.
Of the 8,002 adult participants, 45.8% were men, and the average age was 69.8 (standard deviation = 8.5) years. Over the 5.3-year mean follow-up period, 268 participants died of cancer. Participants who died of cancer were, on average, older, more likely to be men, current smokers, and had history of coronary heart disease. The participants who died of cancer also logged higher levels of total mean sedentary time, longer sedentary bout duration, fewer sedentary time breaks, lower mean levels of light-intensity physical activity (LIPA) and moderate-to-vigorous-intensity physical activity (MVPA).
The physical activity data, when expressed in tertiles, demonstrated a significant relationship with cancer mortality. The total sedentary time and sedentary bout duration in tertile 3 had an 82% (HR, 1.82; 95% CI, 1.27-2.60) and 61% (HR, 1.61; 95% CI, 1.16-2.24) higher risk of cancer mortality, respectively, compared with participants in tertile 1. Once the authors adjusted for additional covariates and MVPA, these associations decreased, but, for total sedentary time, participants in the middle and uppermost tertiles still had a significantly greater risk of cancer mortality compared with those in the lowest tertile (tertile 3 vs. tertile 1; HR, 1.52; 95% CI, 1.01-2.27).
Total sedentary time was significantly associated with the risk of cancer mortality in a linear, dose-response fashion (HR per 1 hour/day increase in total sedentary time: 1.16; 95% CI, 1.03-1.31; P = 0.01). A trend for an association was observed for mean sedentary bout duration and risk of cancer mortality (HR per 1 minute/bout increase in mean sedentary bout duration: 1.01; 95% CI, 1.00-1.02; P = 0.06). To further understand interactions between sedentary time, LIPA, and MVPA, the authors expressed each activity category in 30-minute units and used a partition model that mutually adjusted for all activity categories simultaneously to understand the association with cancer mortality. LIPA and MVPA were associated with a lower risk of cancer mortality, and sedentary time was associated with an increased risk of cancer mortality.
When the authors used isotemporal substitution models replacing 30 minutes of sedentary time with 30 minutes of MVPA, MVPA was associated with a 31% (HR, 0.69; 95% CI, 0.48-0.97) lower risk of cancer mortality. Replacing 30 minutes of sedentary time with 30 minutes of LIPA was associated with an 8% (HR, 0.92; 95% CI, 0.86-0.97) lower risk of cancer mortality.
COMMENTARY
This study adds to the body of research demonstrating less sedentary activity and more physical activity measured with a wearable device are associated with a lower risk of cancer mortality. In particular, replacing sedentary behavior with either MVPA or LIPA by 30 minutes is associated with a lower risk of cancer mortality in a national cohort, including both Black and white participants. The results of this study are similar to a 2015 meta-analysis that revealed sedentary time was associated with a 13% increased risk of cancer mortality (HR, 1.13; 95% CI, 1.05-1.21).4
In contrast, the 2018 Physical Activity Guidelines Advisory Committee determined there was limited evidence suggesting a direct association between sedentary behavior and cancer mortality, with only five of the 13 studies identified in their systematic review reporting a significant association.6 Owing to the fact that many of the studies investigating physical activity and cancer mortality have relied on self-reported physical activity data, the use of accelerometers and other wearable devices in future research studies may help clarify the association between physical activity and cancer mortality.
However, there were a number of limitations to this study. Participants in the larger REGARDS Study who agreed to complete the accelerometer protocol live at a higher socioeconomic status than those who did not agree or were not adherent to wearing the device. Participants who did not agree or were nonadherent with accelerometer use also tended to be older, had a higher frequency of diabetes diagnoses, and had lower survival rates. Thus, the participants included in this study were likelier to reflect a healthier sample. Meanwhile, the accelerometer used in the study did not distinguish between sitting and standing postures, so the authors defined sedentary behavior in relation to intensity of activity. Therefore, sedentary behavior may have been overmeasured. Also, data on tumor characteristics and treatment were not collected, and cancer deaths with site-specific tumors were unavailable. This is important because research demonstrates physical activity and sedentary behavior affect the risk for some, but not all, cancers. This study also had a relatively short follow up period of 5.3 years, with baseline risk factors assessed approximately six years before accelerometer capture. The baseline risk factors may have changed in that time prior to accelerometer measurement, affecting the results of this study.
Although this study has added to the larger body of research, it does not change the current exercise prescriptions that providers should be making to patients with cancer that have been cleared for physical activity. A 2019 International Multidisciplinary Roundtable Consensus Statement recommended an exercise prescription that includes moderate-intensity aerobic training at least three times per week for at least 30 minutes for at least eight to 12 weeks consistently to address health-related outcomes experienced because of a cancer diagnosis and treatment.8 Adding resistance training to aerobic training at least two times per week using at least two sets of eight to 15 repetitions at least 60% of one repetition maximum appears to result in similar benefits, although resistance training alone does not appear to be as effective.8 At this time, there is not enough data on individual types of cancer and treatments to give more precise exercise recommendations.8 Recommending 150 minutes of MVPA weekly for the primary and secondary prevention of cancer is a good recommendation for most patients who have been medically cleared for exercise.9 Patients diagnosed with cancer also should engage in physical activity to tolerance. According to the 2019 International Multidisciplinary Roundtable Consensus Statement, an exercise prescription that includes moderate-intensity aerobic training at least three times per week for at least 30 minutes is important for physical functioning, improving symptoms of depression, anxiety and fatigue, and improving health-related qualify of life.8
REFERENCES
- Siegel RL, Miller KD, Jemal A. Cancer statistics. CA Cancer J Clin 2020;70:7-30.
- Moore SC, Lee IM, Weiderpass E, et al. Association of leisure-time physical activity with risk of 26 types of cancer in 1.44 million adults. JAMA Intern Med 2016;176:816-825.
- Matthews CE, Moore SC, Arem H, et al. Amount and intensity of leisure-time physical activity and lower cancer risk. J Clin Oncol 2020;38:686-697.
- Arem H, Moore SC, Park Y, et al. Physical activity and cancer-specific mortality in the NIH-AARP Diet and Health Study cohort. Int J Cancer 2014;135:423-431.
- Biswas A, Oh PI, Faulkner GE, et al. Sedentary time and its association with risk for disease incidence, mortality, and hospitalization in adults: A systematic review and meta-analysis. Ann Intern Med 2015;162:123-132. Erratum in: Ann Intern Med 2015;163:400.
- Katzmarzyk PT, Powell KE, Jakicic JM, et al; 2018 Physical Activity Guidelines Advisory Committee. Sedentary behavior and health: Update from the 2018 Physical Activity Guidelines Advisory Committee. Med Sci Sports Exerc 2019;51:1227-1241.
- Diaz KM, Howard VJ, Hutto B, et al. Patterns of sedentary behavior and mortality in U.S. middle-aged and older adults: A national cohort study. Ann Intern Med 2017;167:465-475.
- Campbell KL, Winters-Stone KM, Wiskemann J, et al. Exercise guidelines for cancer survivors: Consensus statement from international multidisciplinary roundtable. Med Sci Sports Exerc 2019;51:2375-2390.
- Katzmarzyk PT, Lee IM, Martin CK, Blair SN. Epidemiology of physical activity and exercise training in the United States. Prog Cardiovasc Dis 2017;60:3-10.
In a prospective cohort study of older U.S. adults, replacing sedentary behavior with physical activity was associated with a lower cancer mortality risk.
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