The researchers noted that studies recommending longer periods of activity were based on self-reporting by the participants.
“Previous studies relied on self-reported exposure data for assessing the joint associations between physical activity and sedentary behaviours with mortality. Self-reported assessment of physical activity and sedentary behaviours is prone to misclassification and socialdesirability bias, likely underestimates sedentary time, and has limited validity for estimating both light-intensity and total amount of physical activity. Furthermore, the potential impact of these biases may be compounded when combining information from two self-reported behaviours,” the researchers wrote.
For this study, however, the researchers used activity monitors to track MVPA and sedentary time. The study found 35 minutes of moderate exercise — basically, a brisk walk — gave participants’ the biggest difference in extended life span, but that just 11 minutes also had a positive effect.
In total, 44,370 participants (69.7% women; mean age 65.8 years) were available for meta-analysis. They were followed for 4–14½ years (median 6 years), during which 3,451 (7.8%) participants died.
You can read the full study here.