Is sitting the new smoking? It has long been known that exercise positively impacts our overall health and well-being, but what effect does a lack of exercise have on it? Increasingly, many modern-day conveniences make our lives as convenient and comfortable as possible, but at what cost? While there are many advantages of modern-day living, one unfortunate side effect is the increasingly sedentary lifestyles and behaviors. One-third of the global population aged 15 yrs and older have inadequate physical activity. The increase in physical inactivity is of huge concern as the literature shows that a sedentary lifestyle is directly linked to adverse health outcomes. According to Park et al. (2020), “A sedentary lifestyle has an array of adverse health effects, including elevated all-cause mortality, CVD mortality, cancer risk, risks for metabolic diseases such as DM, HTN, dyslipidemia, and musculoskeletal diseases such as knee pain and osteoporosis.”
Passive Vs. Active Sedentary Behaviors
Increases in TV watching, cell phone usage, and sedentary work environments contribute to the widespread prevalence of sedentary behaviors and the duration of the behaviors. According to Patterson et al. (2018), American adults are sedentary on average 7.7 hours per day, which makes up approximately 55% of our waking hours. In a study analyzing the mortality rates of people with >10 hours and <5 hours of sitting times a day, the sitting time directly correlates with all-cause mortality. It also found that people who watch >6 hours of TV per day have a two-fold increase in all-cause mortality compared to those who watch <2 hours (Hamer et al., 2017). There was some evidence that showing depression correlates with increased sedentary behavior. Passive sedentary behaviors, such as watching TV, were associated with a higher risk of depression than active sedentary behaviors, such as reading or sewing, which did not increase risk (Park et al., 2020).
The prevalence of CVD, hypertension, obesity, and Type 2 DM increase as the duration of sedentary time increases. Dempsey et al. (2018) explain that “prolonged sedentary time reduces the metabolic demands and systemic blood flow, and by stimulating the sympathetic nervous system, it decreases insulin sensitivity and vascular function while increasing the oxidative stress and promoting the low-grade inflammatory cascade.” They also found that non-interactive sedentary behaviors, such as watching TV and sleeping, further increase the risk of hypertension compared to interactive behaviors, such as sitting at a computer or commuting.
Sedentary Time Increases Cancer Risk By 20%
Prolonged sitting is also associated with an increased risk of colorectal, endometrial, ovarian, breast, and prostate cancer and has been shown to increase cancer mortality, particularly in women (Park et al., 2020). In a study by Biswas et al. (2015) that investigated the correlation between sedentary behavior and cancer prevalence, the cancer risk was 13% higher in the group with the longest sedentary time compared to that with the shortest sedentary time. It also reported that sedentary time increased cancer risk by 20%. The increase in hormone-related cancers such as breast and endometrial are linked to the altered circulation levels of sex hormones caused by sedentary behaviors. It also causes a decrease in bone mineral density, increasing the risk of osteopenia or osteoporosis.What
What You Can Do to Off-Set The Impact of Sedentary Behavior
When discussing the importance of physical activity on health, education should emphasize increasing the amount and type of physical activity and reducing the amount of sedentary time per day. Multiple studies show promising that increasing physical activity can offset some of the negative impacts of sedentary behavior. According to Park (2020), “A meta-analysis reported that mortality was not elevated in the people engaging in high levels of moderate-intensity physical activity (60– 75 minutes of moderate-intensity physical activity a day) even when they had >8 hours of sedentary time a day. However, television viewing for >3 hours a day increased the mortality regardless of physical activity, and the people who watched television for ≥5 hours a day showed markedly high mortality.” Additionally, in those with the least physical activity, replacing 30 minutes of sitting time each day with light physical activity reduced the all-cause mortality risk by 14%, and replacing it with moderate to vigorous physical activity reduced the mortality risk by 45%. In a study by Gilchrist et al. (2020), individuals in the top 1/3 of the sedentary group showed a substantially higher cancer mortality risk than those in the bottom 1⁄3. However, replacing 30 minutes of sedentary time with low-intensity physical activity reduced cancer mortality by 8%, and replacing it with moderate to vigorous physical activity reduced it by 31%.
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References:
Hamer M, Yates T, Demakakos P. Television viewing and risk of mortality: Exploring the biological plausibility. Atherosclerosis. 2017 Aug;263:151-155. DOI: 10.1016/j.atherosclerosis.2017.06.024. Epub 2017 Jun 9. PMID: 28645071.
Park JH, Moon JH, Kim HJ, Kong MH, Oh YH. Sedentary Lifestyle: Overview of Updated Evidence of Potential Health Risks. Korean J Fam Med. 2020 Nov;41(6):365-373. doi: 10.4082/kjfm.20.0165. Epub 2020 Nov 19. PMID: 33242381; PMCID: PMC7700832.
Patterson R, McNamara E, Tainio M, de Sa TH, Smith AD, Sharp SJ, et al. Sedentary behaviour and risk of all-cause, cardiovascular and cancer mortality, and incident type 2 diabetes: a systematic review and dose-response meta-analysis. Eur J Epidemiol. 2018;33:811–29.
Rillamas-Sun E, LaMonte MJ, Evenson KR, Thomson CA, Beresford SA, Coday MC, et al. The influence of physical activity and sedentary behavior on living to age 85 years without disease and disability in older women. J Gerontol A Biol Sci Med Sci. 2018;73:1525–31.
Biswas A, Oh PI, Faulkner GE, Bajaj RR, Silver MA, Mitchell MS, 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;162:123–32
Dempsey PC, Larsen RN, Dunstan DW, Owen N, Kingwell BA. Sitting less and moving more: implications for hypertension. Hypertension. 2018;72:1037–46.