Changes in Sitting Time and Cardiovascular Mortality in Older Adults.

INTRODUCTION: Prolonged sitting time has demonstrated consistent associations with increased risk of cardiovascular disease and mortality, but most previous studies have analyzed these associations assessing sitting time at one single point and providing scarce evidence on causal links. The main objective of this study was to analyze the association of 2-year changes in sitting time with subsequent long-term cardiovascular disease mortality in older adults.

METHODS: The analyses were conducted with 2,657 individuals with complete data. Sitting time and physical activity were assessed by questionnaire. Changes in sitting time were classified into consistently sedentary (high sitting time in 2001 and 2003); newly sedentary (low sitting time in 2001 and high sitting time in 2003); formerly sedentary (high sitting time in 2001 and low sitting time in 2003); and consistently nonsedentary (low sitting time in 2001 and 2003). The associations between change in sitting time and cardiovascular disease mortality were summarized with hazard ratios and their 95% CIs obtained from Cox regression. The combined effect of changes in sitting time and physical activity on cardiovascular disease mortality was also examined.

RESULTS: Compared with consistently sedentary participants, those who were consistently nonsedentary had a 33% (hazard ratio=0.67, 95% CI=0.46, 0.96) lower risk of cardiovascular disease death. In combined analyses, consistent nonsedentariness was associated with reduced cardiovascular disease mortality in participants with physical activity less than the median (hazard ratio=0.62, 95% CI=0.39, 1.00) and greater than or equal to the median (hazard ratio=0.49, 95% CI=0.31, 0.79). Formerly sedentary participants with physical activity greater than or equal to the median had a 48% lower cardiovascular disease mortality.

CONCLUSIONS: Among older adults, maintaining low sitting time should be promoted to reduce cardiovascular disease mortality.