Prolonged Sitting Kills
That fact needs to be repeated. Regardless of how much men participated in a formal exercise program, prolonged sitting substantially increased their risk of death.
WARNING: Staring at a computer all day long kills. Mother nature simply did not design humans for prolonged periods of sitting.
While this study only looked at the time spent outside of work, sedentary jobs like truck driving or data entry operators that keep people sitting down all day long, over time will kill these hapless bread winners.
Outside of work, men who spent five or more hours a day sitting were 34 percent more likely to develop heart failure than men who spent no more than two hours a day sitting, regardless of how much they exercised.
"Too much sitting is detrimental to cardiovascular health, independent of regular physical activity." [Young 2014]
UPDATE: Sitting less, moving more
In another armchair study of American adults aged 60 years and older found that being sedentary was an independent risk factor for the inability to perform activities of daily living or the inability to live independently caring for oneself doing very basic stuff like eating, dressing, and bathing; which the researchers called a disability. What was different about this study was that it provided some hard numbers. Being sedentary dramatically increased the risk of disability only when it exceeded 64% of the awake hours of the population studied, or was greater than 8.9 hours out of a total of 14 for each day.[Dunlop 2014]
In conclusion, the Natural Health Perspective recommends that people when they retire better not plan on watching a lot of television or doing a lot of computer work. Nevertheless, whenever you do, try changing it up a bit, by standing as much as possible. As well as taking long and frequent breaks doing something physical that will at least distribute any periods of sitting more evenly throughout the day. In addition, you could try different ways of sitting, such as on an inflatable exercise ball, or even kneeling on the floor.
Health Risks of Prolonged Sitting
While this particular study only looked at men, the Natural Health Perspective sees no reason why women wouldn't be adversely affected by prolonged sitting.
The adverse health effects undoubtedly, go beyond sitting down. Prolonged bed rest during periods of illness is also very bad for your health. Remember that your immune system uses walking to pump its lymphatic fluids throughout your body. This is why hospital workers are always trying to get hospital patients to walk around.
Realistically, you are going to be awake approximately 16 hours a day. As long as you are active or standing for 50% of that time or approximately 8 hours, you can be considered active at a minimally acceptable level. While being able to live independently does not equate to heart failure, it at least provides a starting point for determining how much sitting time is acceptable.
In addition, it would be predicable that an inactive lifestyle outside of work would result in both weight gain and shortness of breath, during Middle-Age and beyond; even though this research study did statistically factor out the confounding effects of body weight.