Physicians' Academy for Cardiovascular Education

Various sedentary behaviours differentially affect mortality risk

Basterra-Gortari FJ et al., J Am Heart Assoc. 2014 - J Am Heart Assoc. 2014 Jun 25;3(3)

 

Television viewing, computer use, time driving and all-cause mortality: the SUN cohort

 
Basterra-Gortari FJ, Bes-Rastrollo M, Gea A et al., 
J Am Heart Assoc. 2014 Jun 25;3(3):e000864. doi: 10.1161/JAHA.114.000864.

 
Background

Epidemiological research has traditionally focussed on the effects of physical activity on health, and the benefits are well known. The absence of moderate-to-vigorous physical activities is often considered a ‘sedentary lifestyle’, although too much time spent sitting can coexist with high levels of physical activity. Thus, sedentary lifestyles deserve further consideration.
Sitting time during leisure, total sitting time or television viewing have been described to be associated with all-cause mortality, after adjustment for physical activity [1-3].A study in Dutch adults (18-28 years) described that television viewing, but not computer use, was directly associated with triglyceride levels and insulin concentrations [4], and similar distinct relationships with biomarkers for cardiovascular disease were observed in British adults (44-45 years) [5].
This study aimed to assess the association between different types of sedentary behaviours (television viewing, computer use, and time driving) and all-cause mortality, independently from physical activity levels, in the prospective SUN cohort study of Spanish university graduates (“Seguimiento Universidad de Navarra”, University of Navarra follow-up)[6].
 

Main results

  • Television viewing was positively associated with all-cause mortality, after adjustment for age, sex, smoking, total energy intake, Mediterranean diet adherence, BMI, computer use and time spent driving. Each additional 2-hours viewing per day gave a higher risk of IRR (incidence rate ratio): 1.40, (95%CI: 1.06-1.84). 
  • Time spent using a computer or driving were not significantly associated with mortality. Each additional 2 hours/day of computer use (IRR: 0.96, 95%CI: 0.79-1.18) or driving (IRR: 1.14, 95%CI: 0.90-1.44) did not affect mortality.
  • Longer total sedentary behaviour was directly associated with total mortality, after multivariable adjustment (IRR per each additional 2 hours/day: 1.17, 95%CI: 1.03-1.33).
  • 19 deaths due to cardiovascular disease occurred in 8.2 years of follow-up (multivariably adjusted IRR for each additional 2 hours/day of television viewing: 1.44, 95%CI: 0.87-2.41).
  • As a sensitivity analysis, the analysis was further adjusted for snacking and consumption of sugar-sweetened beverages. All-cause mortality IRR for each additional 2 hours/day of television viewing was 1.46 (95%CI: 1.10-1.93).
 

Conclusion

This analysis shows that total sitting time is associated with higher risks of all-cause mortality, after adjusting for physical activity and other potential confounders. Not all types of sedentary behaviour infer the same risk, as television viewing was associated with a higher mortality risk, but computer use or time spent driving were not.
The relationship between television viewing and all-cause mortality could not be explained by snacking and consumption of sugar-sweetened beverages. Also reverse causation is not likely the explanation for the findings in this relatively healthy cohort. Further studies should confirm the effect of computer use and driving on mortality, and determine the biological mechanisms underlying these associations.
 
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References

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