Physical inactivity and death

Clinical bottom line

Physical inactivity in patients with multiple chronic conditions is associated with approximately twice the risk of death, compared with a minimum of 30 minutes a day, once a week.

The association between physical inactivity and ill health is unequivocal. This paper examines the impact of physical inactivity on death, in patients with chronic disease.

Reference

BC Martinson et al. Physical inactivity and short-term all-cause mortality in adults with chronic disease. Archives of Internal Medicine 2001 161: 1173-1180.

Study

Participants were 1,832 members of a US health plan, aged at least 40 years (with an average age of 63 years), with two or more chronic health conditions (hypertension, coronary heart disease, diabetes mellitus or dyslipemia; classified using the International Classification of Diseases, Ninth Revision). There were approximately equal numbers of men and women. In 1995, participants completed mailed questionnaires on demographics, health status and health-related behaviours. They were followed for three and a half years. Deaths were confirmed using the Minnesota Death Index.

Physical activity was assessed with two questionnaires:

measured how many times a week participants reported engaging in mild, moderate or strenuous exercise for more than 15 minutes (and were categorised into tertiles);
measured how many days in the previous week participants reported engaging in physical activity for 30 minutes or more.

Results

There were 197 deaths during the three and a half year follow-up period.

Results were adjusted for age, gender, smoking, functional impairment and co-morbidity (19 chronic conditions, scored as a sum of their weights).

Older age was associated with higher mortality; with 11.4 years more than doubling the likelihood of death. Women were less likely than men to have died during the follow-up period. Current smokers were about twice as likely to die as non-smokers. Being functionally impaired was associated with an approximate 70% increased risk of death. A high co-morbidity score was associated with a significantly higher likelihood of death.

Similar results were obtained with both measures of physical activity.

The risk of death was doubled for those in the lowest tertile of activity compared with those in the middle or highest tertiles (mortality rate ratio 2.01).
Less than 30 minutes physical activity in the previous week was associated with twice the risk of death, compared with 30 minutes or more (mortality risk ratio 2.15).

Comment

There are several details worth noting about this study.

As participants had multiple chronic conditions their activity level was generally low, so it shows a benefit of activity at low-intensity levels.
It examined the risk of mortality in the short term, i.e. just over three years.
Inactivity in these patients may, to some extent, be associated with other factors that increase mortality risk. While some were considered (e.g. functional impairment, co-morbidity), others were not (e.g. dietary factors), so there is the possibility that these explain some of the association observed between inactivity and mortality.
It measured present activity levels; it did not measure lifetime activity or changes in activity during the study period, so the observed relationship between activity and mortality could be the result of previous years' exercise. However, there is plenty of evidence that recent activity results in many beneficial physiological changes.

Finally, some older adults, particularly those with medical conditions and those who have been sedentary for a long time, are fearful of exercise. This study may help to allay those fears. Even a minimum amount of a low level activity, such as walking, can produce substantial health benefits.