NEW YORK (Reuters Health) – Hospitalized elderly patients appear to be protected against the development of delirium if they have participated in activity, especially regular physical exercise, according to study findings published in the August issue of the Journal of the American Geriatrics Society.

“Delirium is a common, life-threatening clinical syndrome that is preventable,” Dr. Frances M. Yang, of Harvard Medical School, Boston, Massachusetts, and colleagues write. “Given its high prevalence and incidence and its association with poor outcomes, finding mechanisms to prevent delirium remains a high priority.”

In a prospective cohort study, the researchers examined factors associated with delirium in a total of 779 newly hospitalized patients taken from two prospective studies. The subjects were at least 70 years of age and were free of dementia.

The team found a significant association between higher levels of education and a lower cumulative risk for delirium (per year of education, odds ratio (OR) = 0.92). More participation in activity was also related to a lower risk for delirium (OR = 0.65). In multivariable analysis, engagement in activity mediated the relationship between education and risk for delirium.

When each activity was considered separately, only regular exercise significantly lowered the risk for developing delirium (OR = 0.76).

The authors report that there was a dose-response relationship between exercise participation and the risk of delirium. Compared to subjects who exercised less than once per month, those who exercised between one and four times per month had an OR of 0.76. Those who exercised at least five times per months had an OR 0.57.

“The mechanism by which regular physical exercise improves cognitive functioning in older adults appears to operate through increases in gray and white matter volume in the prefrontal and temporal cortices, where age-related brain volume loss occurs,” Dr. Yang and colleagues explain. “Therefore, older patients who engage in regular exercise may experience less neural decline and higher maintenance of brain volume and may also better withstand common precipitants of delirium.”

J Am Geriatr Soc 2008;56:1479-1484.