It is not just the amount of time spent sitting but also the way in which sitting time is accumulated during the day that increases the risk of early death.
Researchers found that adults who sit for one to two hours at a time without moving have a higher mortality rate than adults who accrue the same amount of sedentary time in shorter bouts.

Researchers suggest that those who have a job or life style that involves sitting for prolonged periods of time should take a movement break every 30 minutes!!

In the largest study to link objectively measured sedentary time and sedentary patterns with mortality risk, researchers found that participants who kept most of their sitting bouts to less than 30 minutes had the lowest risk of early death
Researchers say they do not yet know precisely how much activity is optimal but advise against continuous sedentary patterns!
The Mirror-