Thanks to advances in cancer screening and treatment technologies, the number of cancer survivors worldwide has increased dramatically. Therefore, the prognosis management of cancer survivors is particularly important.
Recently, a new study from lin Yang's team at the University of Calgary in Canada showed that cancer survivors' active physical activity was associated with a 66% lower risk of all-cause death compared with cancer survivors who lacked physical activity; compared with cancer survivors who spent less than 6 hours a day sedentary, sitting for more than 8 hours a day was associated with an 81% increased risk of all-cause death; and cancer survivors who were sedentary for more than 8 hours a day and had the highest risk of death. The findings were published in JAMA Oncology, a top journal in the field of oncology[1].
Due to technological advances in early cancer screening and treatment, coupled with an aging population, the global population of cancer survivors is growing rapidly [2]. Many cancers and cancer treatments have adverse effects, shortening the life expectancy of cancer patients [3]. Therefore, there is an urgent need to develop viable strategies to improve the long-term health of cancer survivors.
Physical activity has long been considered a healthy lifestyle, and many studies have shown that physical activity is associated with a reduced risk of common chronic diseases [4] and can also improve cancer survival before and after diagnosis [5]. Physical activity may improve cancer survival through three pathways: one is to have a direct impact on tumor growth and metastasis, the second is to improve the completion rate of treatment, and the third is to improve the effectiveness of treatment [6].
There is evidence that the health effects of physical activity in cancer survivors are more pronounced than before cancer diagnosis [7]. However, levels of physical activity among cancer survivors are very low—more than one-third sit for long periods of time with little or no physical activity [8].
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In healthy people, adequate physical activity has been shown to counteract the negative effects of sedentary behavior [9-10]. Cancer survivors may be more likely to remain sedentary due to comorbidities and functional degradation associated with cancer and cancer treatment. However, epidemiological evidence between sedentary time and physical activity and the risk of death in cancer survivors remains sparse.
Therefore, the main purpose of Yang's research is to explore the independent and joint associations between sedentary and physical activity in cancer survivors and the risk of all-cause death, cancer and non-cancer death.
The researchers used data from the National Health and Nutrition Survey (NHANES) cohort, which included 1535 cancer survivors, 60.1 percent of whom were women, with an average age of 65.1 years. During a median follow-up period of 9.0 years, 293 cancer survivors died, of whom 114 died of cancer, 41 from heart disease and 138 from other causes of death.
After adjusting for a range of confounding factors, the findings showed that sitting for more than 8 hours a day in cancer survivors was associated with an 81% increased risk of all-cause death and a 127% increased risk of cancer death compared to less than 4 hours a day. Each hour increase in daily sedentary time was associated with a 7% and 9% increased risk of all-cause death and cancer death (Table 1).
Table 1: Sedentary, physical activity and all-cause and exogenous death
The researchers grouped physical activity, defining more than 150 minutes per week as the active physical activity group and less than 150 minutes per week as the lack of physical activity. The results showed that cancer survivors who were actively physically active were associated with a 66% lower risk of all-cause death and a 68% lower risk of cancer death compared to the inactive group. These associations are significant in both male and female, obese and non-obese cancer survivors.
The researchers then performed a hierarchical analysis of physical activity, and the results showed that among cancer survivors who were actively physically active, sedentary behavior was not found to be associated with the risk of death. However, in cancer survivors who lack physical activity, longer sedentary behavior was significantly associated with an increased risk of death, in a dose-response relationship, i.e., every 1 hour increase in sedentary time was associated with an 8% increase in the risk of all-cause death and a 9% increase in the risk of cancer death.
In the joint analysis, the researchers found that cancer survivors with inactive inactivity had the highest risk of death from sitting for more than 8 hours a day, with a risk ratio of 5.38 (95% CI: 2.99-9.67) compared with cancer survivors who were actively physically active and sedentary for less than 6 hours (Table 2). Subsequently, the researchers excluded cancer survivors who died within 2 years of the follow-up period and got the same results.
Table 2: Combined effects of sedentary and physical activity on the risk of death
Finally, Yang's research team also illustrates several limitations of the study. First, sedentary and physical activity information in the study was obtained through patient self-reporting rather than objective measurements through wearable devices; second, sedentary behavior and physical activity were measured at baseline and did not reflect dynamic changes in patient behavior during follow-up; and finally, NHANES did not collect tumor staging and treatment information from cancer patients, which could create reverse causation.
Overall, in this prospective cohort study of a nationally representative sample of cancer survivors in the United States, the researchers found that sedentary and physical inactivity in cancer survivors were associated with an increased risk of all-cause and cancer death. Future studies need to further elucidate these associations and require substantial evidence to quantify the timing, dose, limits, and types of sedentary behavior and physical activity to increase survival among cancer survivors.
bibliography:
[1] Cao C, Friedenreich CM, Yang L. Association of Daily Sitting Time and Leisure-Time Physical Activity With Survival Among US Cancer Survivors [published online ahead of print, 2022 Jan 6]. JAMA Oncol. 2022;10.1001/jamaoncol.2021.6590. doi:10.1001/jamaoncol.2021.6590
[2] Global Burden of Disease Cancer Collaboration, Global Burden of Disease Cancer Collaboration. Global, regional, and national cancer incidence, mortality, years of life lost, years lived with disability, and disability-adjusted life-years for 29 cancer groups, 1990 to 2017: a systematic analysis for the Global Burden of Disease study. JAMA Oncol. 2019;5(12): 1749-1768. doi:10.1001/jamaoncol.2019.2996
[3] Jensen RE, Potosky AL, Moinpour CM, et al. United States Population-Based Estimates of Patient-Reported Outcomes Measurement Information System Symptom and Functional Status Reference Values for Individuals With Cancer. J Clin Oncol. 2017;35(17):1913-1920. doi:10.1200/JCO.2016.71.4410
[4] Janssen I, Clarke AE, Carson V, et al. A systematic review of compositional data analysis studies examining associations between sleep, sedentary behaviour, and physical activity with health outcomes in adults. Appl Physiol Nutr Metab. 2020;45(10 (Suppl. 2)):S248-S257. doi:10.1139/apnm-2020-0160
[5] Friedenreich CM, Stone CR, Cheung WY, Hayes SC. Physical activity and mortality in cancer survivors: a systematic review and meta-analysis. J Natl Cancer Inst Cancer Spectr. 2019;4(1):pkz080. doi:10.1093/jncics/pkz080
[6] Yang L, Morielli AR, Heer E, et al. Effects of Exercise on Cancer Treatment Efficacy: A Systematic Review of Preclinical and Clinical Studies. Cancer Res. 2021;81(19):4889-4895. doi:10.1158/0008-5472.CAN-21-1258
[7] Schmitz KH, Campbell AM, Stuiver MM, et al. Exercise is medicine in oncology: Engaging clinicians to help patients move through cancer. CA Cancer J Clin. 2019;69(6):468-484. doi:10.3322/caac.21579
[8] National Cancer Institute. Cancer survivors and physical activity. 2021. Accessed July 16, 2021. https://progressreport.cancer.gov/after/physical_activity
[9] 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 [published correction appears in Ann Intern Med. 2015 Sep 1;163(5):400]. Ann Intern Med. 2015;162(2):123-132. doi:10.7326/M14-1651
[10] Ekelund U, Steene-Johannessen J, Brown WJ, et al. Does physical activity attenuate, or even eliminate, the detrimental association of sitting time with mortality? A harmonised meta-analysis of data from more than 1 million men and women [published correction appears in Lancet. 2016 Sep 24;388(10051):e6]. Lancet. 2016;388(10051):1302-1310. doi:10.1016/S0140-6736(16)30370-1
Responsible editor 丨 Wang Xuening