One of the more interesting results from the study of health and lifestyle choices in recent years is the finding that time spent sitting correlates with increased mortality and a shorter life expectancy regardless of whether or not individuals also exercised. As for all such statistical investigations, there is a lot of room to speculate as to the web of related associations and which of them are actually contributing meaningfully to differences in health. This metastudy expands on the picture by looking specifically at cancer risk:
Sedentary behavior is emerging as an independent risk factor for chronic disease and mortality. However, the evidence relating television (TV) viewing and other sedentary behaviors to cancer risk has not been quantitatively summarized. We performed a comprehensive electronic literature search for published articles investigating sedentary behavior in relation to cancer incidence. Because randomized controlled trials are difficult to perform on this topic, we focused on observational studies that met uniform inclusion criteria.
Data from 43 observational studies including a total of 68936 cancer cases were analyzed. Comparing the highest vs lowest levels of sedentary time, the relative risks (RRs) for colon cancer were 1.54 for TV viewing time, 1.24 for occupational sitting time, and 1.24 for total sitting time. For endometrial cancer, the relative risks were 1.66 for TV viewing time and 1.32 for total sitting time. A positive association with overall sedentary behavior was also noted for lung cancer. Sedentary behavior was unrelated to cancers of the breast, rectum, ovaries, prostate, stomach, esophagus, testes, renal cell, and non-Hodgkin lymphoma.
[We conclude that] prolonged TV viewing and time spent in other sedentary pursuits is associated with increased risks of certain types of cancer.