Disturbed Rest-Activity Rhythms Strongly Associated With Mortality Rates In Older Men

The study, funded by the National Institute on Aging and authored by Misti L. Paudel, of the University of Minnesota-Twin Cities in Minneapolis, focused on 3,053 community-dwelling men aged 67 years and older. Rest/activity biological rhythms were obtained, and specific measures of these rhythms included the time of the peak of the rest/activity rhythm (acrophase), the height of the rest/activity rhythm (amplitude) and the robustness or strength of the rest/activity rhythm (F-value). Each was expressed as quintiles (i.e., the data were distributed into five equal parts, each containing a fifth of the sample population).

All models were controlled for multiple potential confounders, including age, race, alcohol, health status, impairments in activities of daily living scale, and common medical conditions. The results showed that men with the lowest amplitude (i.e., lowest quintile) had higher mortality rates than men with the highest amplitude (i.e. highest quintile). A similar association was observed between men with less robust rhythms and higher rates of mortality. There was a U-shaped association between mortality rates and timing of peak activity (acrophase), with mortality rates greatest in men with the earliest and latest time of peaks of the rest/activity rhythms (furthest from the mean).

"The association between rest/activity rhythm disruptions and mortality has been studied in cancer patients and older, institutionalized adults with Alzheimer disease," said Paudel. "However, our study is the first to report strong associations between characteristics of rest-activity rhythms and death in older, community-dwelling (non-institutionalized) men. It is uncertain whether the relationship between rest/activity circadian rhythms and mortality in older people is causal, or whether rest/activity circadian rhythms represent a potent biomarker related to increased risk of death. More research is needed in order to understand the physiologic and biological mechanisms underlying these associations, as well as the contribution of poor health."

Not sleeping well can lead to a number of problems. Older adults who have poor nighttime sleep are more likely to have a depressed mood, attention and memory problems, excessive daytime sleepiness, more nighttime falls and use more over-the-counter or prescription sleep aids. In addition, recent studies associate lack of sleep with serious health problems such as an increased risk of obesity, cardiovascular disease and diabetes.