If you watch TV daily for at least 2 to 3 hours your risk of developing diabetes type 2, having nonfatal cardiovascular disease and dying from any cause is higher, researchers from the University of Southern Denmark and Harvard School of Public Health revealed in JAMA (Journal of the American Medical Association.
In many parts of the world, watching TV, working and sleeping are the three most commonly reported daily activities. Americans watch TV for an average of 5 hours each day.
The authors wrote as background information:
"Beyond altering energy expenditure by displacing time spent on physical activities, TV viewing is associated with unhealthy eating (e.g., higher intake of fried foods, processed meat, and sugar-sweetened beverages and lower intake of fruits, vegetables, and whole grains) in both children and adults. Physical inactivity, various dietary factors, and smoking are well-established independent risk factors of type 2 diabetes, cardiovascular disease, and all-cause mortality. Because TV viewing is the most prevalent and pervasive sedentary behavior, there is a great deal of interest in quantifying its independent association with health outcomes. However, a systematic and quantitative assessment of published studies is not available."
Anders Grontved, M.P.H., M.Sc., and Frank B. Hu, M.D., Ph.D., gathered data from several published prospective cohort studies that investigated possible links between time spent watching TV and diabetes type 2 incidence, as well as nonfatal and fatal cardiovascular disease, and all-cause mortality. The published material dated from 1970 through March 2011.
They eventually included 8 studies in their analysis:
- Four studies, involving 175,938 people focused on diabetes type 2 - there were 6,428 incident cases during an 8.5-year follow-up (average).
- Four studies focused on non fatal cardiovascular disease and involved 34,253 people - there were 1,052 incident cases during a 10.4-year follow-up.
- Three studies looked at all-cause mortality, and involved 26,509 individuals - there were 1,879 deaths during a 6.8-year follow-up.
The authors wrote:
"While the associations between time spent viewing TV and risk of type 2 diabetes and cardiovascular disease were linear, the risk of all-cause mortality appeared to increase with TV viewing duration of greater than 3 hours per day."
Based on US incidence rates, the investigators calculated that the absolute risk difference (cases per 100,000 people annually) per 2 hours watching TV each day was 104 for all-cause mortality, 38 for fatal cardiovascular disease, and 176 for type 2 diabetes.
The authors wrote:
"It is biologically plausible that prolonged TV viewing is associated with type 2 diabetes, cardiovascular disease, and all-cause mortality. Numerous prospective studies have reported associations of TV viewing with biological risk factors for these outcomes including obesity, adverse lipid levels, and clustered cardiovascular risk; however, some studies did not report these associations. Furthermore, associations of sedentary behaviors analogous to TV viewing (e.g., sitting during work or while driving) with type 2 diabetes, fatal or nonfatal cardiovascular disease, and all-cause mortality have been reported in cohort studies.
Additional research quantifying the mediating influence of diet and physical inactivity is warranted. Future research also should assess the association of prolonged daily use of new media devices on energy balance and chronic disease risk."
Written by Christian Nordqvist