Is sitting for a long time so bad?

Is sitting for a long time so bad?

Sitting for prolonged period can affect health even in those who follow the physical activity guidelines. It is still worse in those who do not follow the guidelines for physical activity. In fact, sitting for more than five hours a day has been considered to carry a risk equivalent to that of smoking. But heavy smoking of more than 40 cigarettes per day carries a relative risk of death of 4.08, while sedentary behaviour has a hazard ratio of 1.22. So sitting cannot be considered as ‘new smoking’ though sedentary behaviour is not desirable. Sitting time would include sitting at work, television viewing time and similar static leisure activities as well as time spent traveling in automobiles. Any situation with low energy expenditure like sitting, reclining or lying posture is called sedentary behaviour.

An interesting study evaluated the physical activity, sedentary time and heart health risk in heavy goods vehicle drivers. It involved 329 heavy goods vehicle drivers from United Kingdom. Nearly 90% of the drivers were overweight or had obesity. Pre-diabetes or diabetes was found in about 12 % and high blood pressure in about 30%. Increased levels bad cholesterol (LDL) was noted in over 80%. The drivers had 12 hours/day of sitting on workdays. They had about 2 hours/day of light physical activity and nearly 10 minutes/day of moderate to vigorous physical activity. This should be considered in the background of the recommended minimum of 30 minutes of moderate to vigorous physical activity per day.

A study using CT coronary angiography enrolled about 200 persons at annual medical check ups. Sitting time was classified as short if less than 5 hours/day, moderate if between 5 to 9 hours and long if 10 hours or more. Increased sitting was associated with higher amounts of fat deposits in the blood vessels of the heart. This was noted even after accounting for age, gender, associated diseases, body mass index and blood fat levels.

A review of 47 studies assessed sedentary behaviour in adults adjusted for physical activity. They concluded that prolonged sedentary time was independently associated with deleterious health results regardless of physical activity. The results evaluated were heart disease, diabetes, cancer and all-cause deaths. Significant risk was found for all-cause deaths, heart disease deaths, occurrence heart disease, cancer deaths and occurrence of diabetes. The effects were generally more pronounced at lower levels of physical activity than at higher levels.

Another review had over 700 000 participants with long follow up. They found that sedentary time increased risk of heart disease only at very high levels. Highest sedentary time group in their analysis was sedentary time of 12.5 hours/day while the lowest sedentary time group was 2.5 hour/day.

An earlier report of six studies had information on nearly 600 000 persons. They also found that the association between daily total sitting time and all-cause deaths was not a steady increase. They estimated a 34% higher mortality risk for adults sitting 10 hours/day, after taking physical activity into account. They also noted that moderate to vigorous physical activity appeared to reduce the risk of high amounts of daily sitting time in relation to all-cause deaths.

Sitting for a long time can lead to obesity, mostly over the tummy, with increased blood pressure, chance for type 2 diabetes mellitus and high blood fat levels, constituting what is called as metabolic syndrome. Standing desks at work are being promoted to avoid prolonged sitting. This is in addition to methods of enhancing physical activity at work like using stairs instead of lift and having the parking slot a bit away to mandate walking. Prolonged sitting can also be linked to back pain, tortuous enlarged blood vessels in the legs (varicose veins) and even dangerous clots in blood vessels of the legs (deep vein thrombosis) in situations like long haul flights. Working for long periods on a computer in an ergonomically unfavourable posture can get you pain in the neck as well.