24-hour rest-activity rhythms linked to rate of biological aging

Adults with stronger and more consistent daily patterns of rest and activity showed signs of slower aging, as measured by blood tests, in a study led by researchers at the Johns Hopkins Bloomberg School of Public Health.

The researchers analyzed data on 207 adults in the long-running Baltimore Epidemiologic Catchment Area (ECA) cohort study. They compared rest-activity rhythm data from wrist-worn devices with blood tests that measure biological aging.

The results showed that stronger rhythms, characterized by bigger differences between daytime and nighttime activity levels, as well as less fragmented rest-activity rhythms—meaning longer, more sustained periods of activity or rest—and greater day-to-day rhythm consistency were significantly associated with more youthful physiological age scores. These associations were present after accounting for the participants’ chronological ages and other relevant factors, including sex, education level, and certain health conditions.

The study was published online May 7 in JAMA Network Open.

“Our findings suggest rest-activity rhythms may be useful markers of the rate of physiological aging in adults. If supported by future research, these rhythms might emerge as potential targets for interventions to slow the aging process,” says Adam Spira, PhD, study co-senior author and a professor in the Bloomberg School’s Department of Mental Health.

The other co-senior author, Brion Maher, PhD, is also a professor in the Bloomberg School’s Department of Mental Health. The study’s lead author was Chunyu Liu, a PhD student supervised by Maher and Spira.

Scientists use wearable “actigraph” devices to track the rest and activity patterns of individuals going about their ordinary lives. Another recent study by Spira and colleagues linked weaker and more fragmented rest-activity rhythms to brain atrophy in older adults; other researchers have linked weaker rest-activity rhythms to greater risks of mild cognitive impairment and dementia, psychiatric disorders, and even cancers.

Rest-activity rhythms typically weaken in later life, but the chronological age of an older adult may not reflect actual biological decline. Long-term exposure to factors such as high blood sugar, systemic inflammation, and cigarette smoke accelerates the aging process throughout the body. In recent years, scientists have developed blood tests to measure the degree of this “physiological aging” by analyzing changes in epigenetic marks—small chemical modifications on DNA that can change over time.

In the new study, the researchers tracked participants’ rest-activity rhythms over approximately seven consecutive 24-hour periods. Rest could include sedentary activities such as sitting and reading a book or eating a meal, as well as daytime napping and nighttime sleep; participants also kept nap/sleep logs. The researchers then compared each participant’s rest-activity rhythms with their scores on four standard “epigenetic clocks”—physiological age estimates derived from blood samples—known as Horvath, Hannum, PhenoAge, and GrimAge.

The study participants had an average chronological age of about 68 years.

The results showed that stronger and more regular rest-activity rhythms were associated with significantly lower physiological age scores on the GrimAge and PhenoAge epigenetic clocks. A similar association was found for the Horvath and Hannum scores, though in those cases the association did not reach statistical significance. The links between rest-activity rhythms and physiological age scores were more pronounced among female and in white participants.

The study, which the researchers considered exploratory, examined only a “cross-sectional” snapshot of rest-activity rhythms and physiological aging scores at approximately the same time for each participant.

“We suspect that the associations we found in this study sample underestimate what is going on in the general population,” Maher says. “We were looking at adults who had survived to older ages and were healthy enough to participate in the research, which meant that we were not looking at adults who aged more rapidly and had already died or were too unhealthy to participate.”

“We definitely need to do longitudinal studies over time, to see whether the weakening of rest-activity rhythms precedes physiological aging acceleration or vice-versa,” Liu says.

The scientists expect that research in this field will someday enable older adults and/or their doctors to monitor markers of physiological aging or other health risks via their wearable devices.

The researchers also hope to conduct clinical trials to determine whether making rest-activity rhythms stronger and more consistent can slow the physiological aging process.

This article was originally published on Newswise: All Journal News.