THE BACK PAGE RESEARCH REVIEW Is sitting the new smoking? REVIEWED BY SHAWN THISTLE Study title: Sedentary time and its association with risk for disease incidence, mortality, and hospitalization in adults Authors: Biswas A, Oh PI, Faulkner GE et al. Publication information: Annals of Internal Medicine 2015; 162(2): 123–132. D espite the health-enhanc-ing benefits of physical activity, this alone may not be enough to reduce the risk of disease and illness. Population-based studies found more than half of an average person’s work-ing day involves sedentary activities associated with prolonged sitting. Studies suggest long periods of sitting have deleterious health effects inde-pendent of adults meeting physical activity guidelines. The objective of this meta-analysis was to quantitatively evaluate the asso-ciation between sedentary time and health outcomes independent of physi-cal activity participation among adult populations. It was hypothesized that sedentary time would be independently associated with both cardiovascular and non-cardiovascular outcomes after ad-justing for participation in physical ac-tivity. A further predication was that the relative hazards associated with seden-tary times would be attenuated in those who participate in higher levels of phys-ical activity compared to lower levels. A total of 20,980 studies were identi-fied through database searching and 25 studies were added after hand-searching in-text citations. No randomized con-trolled trial met the selection criteria. Most studies used prospective cohort study designs and three studies used cross-sectional and case-control study designs. Definitions of sedentary time varied across studies. There was statistical evidence of pub-lication bias among studies reporting all-cause mortality. No statistical evi-dence of publication bias was found for cardiovascular disease mortality and cancer mortality. Publication bias was not assessed for cardiovascular disease incidence and type II diabetes incidence because the small number of studies may overestimate the effects of bias. Heterogeneity across studies report-ing all-cause mortality and cardiovascu-lar disease incidence, as outcomes, may be high. Heterogeneity was low for cardiovascular disease mortality, cancer mortality, cancer incidence and type II diabetes incidence. cent lower risk of potentially preventa-ble hospitalization [HR 0.86 (CI 0.83-0.89)]. Ten studies reported the effects of prolonged bouts of sedentary time mod-ified by the highest or lowest reported participation in physical activity and health outcomes. The relative hazards associated with sedentary time on out-comes varied according to physical ac-tivity levels and were generally more pronounced at lower levels than at higher levels. Sedentary time was asso-ciated with a 30 per cent lower relative risk for all-cause mortality among those with high levels of physical activity [pooled HR 1.16 (CI 0.84-1.59)] as compared with low levels of physical activity [pooled HR 1.46 (CI 1.22-1.75)]. This study demonstrated sedentary time was independently associated with a greater risk for all-cause mortality, cardiovascular disease incidence or mortality, cancer incidence or mortality and type II diabetes in adults. The del-eterious outcomes associated with sed-entary time generally decreased in magnitude among persons who partic-ipated in higher physical activity com-pared to lower levels. In other words, prolonged sedentary time, independent of physical activity, is positively associated with various dele-terious health outcomes. The results reaffirm the need for greater public awareness about the hazards associated with sedentary behaviours. The results also justify the necessity for further re-search to explore the effectiveness of interventions designed to target seden-tary time independently, and in addi-tion, to those targeting physical activity. The most important take home mes-sage for your practice is GET YOUR PATIENTS MOVING! www.canadianchiropractor.ca Conclusions, application Pertinent results Greater sedentary time was found to be positively associated with an increased risk of all-cause mortality, cardiovascu-lar disease mortality, cancer mortality, cardiovascular disease incidence, cancer incidence and type II diabetes inci-dence. The largest statistical effect was associated with the risk for type II dia-betes [pooled hazard ratio (HR) 1.91 (CI 1.64-2.22)]. Among studies assess-ing cancer mortality and incidence, significant associations were found for breast, colon, colorectal, endometrial and epithelial ovarian cancer. One study evaluated whether sedentary behaviour was correlated with potentially modifi-able hospitalization, revealing that self-reporting fewer than eight hours of sitting time per day resulted in a 14 per DR. SHAWN THISTLE, DC, is the founder and CEO of RRS Education (rrseducation.com), which helps busy clinicians integrate current research evidence rationally into practice. He also maintains a practice in Toronto, lectures at CMCC and provides chiropractic medicolegal consulting services. Reach him at: shawn@rrseducation. 46 Canadian Chiropractor December 2015
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