Long periods of sitting are associated with obesity, type 2 diabetes, some cancers and early death, although the evidence shows a link and not proof of cause.
The advice for all ages is to sit less and to break up sitting time, for example by standing up every 30 minutes.
Many adults in the United Kingdom spend most of their waking hours sitting: at desks, in cars and on public transport, and in front of screens at home. Long periods of sitting are associated with poorer health, and the official activity guidelines advise people of all ages to sit less and to break up the time they do spend seated.
The NHS links inactivity with being overweight or obese, type 2 diabetes, some types of cancer and early death. Sitting for long periods is thought to slow the metabolism, which affects the body's ability to regulate blood sugar and blood pressure and to break down fat.
The link was first noticed in the 1950s, when researchers found that the drivers of London's double-decker buses were twice as likely to have heart attacks as the conductors. The drivers sat for about nine-tenths of their shifts; the conductors climbed about 600 stairs a day.
Most of the evidence is of this observational kind. It shows an association between sitting and ill health, not proof that one causes the other, and the NHS states that there is not enough evidence to set a limit on the hours an adult should sit each day.
Sitting less and exercising more are separate recommendations. A person can meet the weekly target of 150 minutes of activity and still spend the rest of the day seated. Research suggests that high levels of activity offset much of the risk associated with sitting, but the advice remains to do both.
The NHS suggests:
Employers have a legal duty to assess the risks of work at display screens, which includes providing for breaks or changes of activity.
Some older adults spend nine hours or more a day sitting. The NHS advice is to avoid long periods in front of a television or computer, to stand up and move during advertisement breaks, to stand or walk while on the telephone, to use the stairs as much as possible, and to take up active hobbies such as gardening and walking or dance groups.
Long sitting also stiffens the hips and back and contributes to aches in the neck and shoulders; see posture. The activity targets are set out under physical activity guidelines.