Too much sleep for people between 80 and 105 years old is tied to higher mortality rates, according to a new research paper published in JAMDA.

While both too much and not enough sleep can have negative ramifications for people of all ages, like obesity, cardiovascular disease, and diabetes mellitus, sleeping too much seems to have a negative impact for the oldest age cohorts, authors said.

While cognitive impairment contributes to higher mortality in this population, the research in “The Role of Cognitive Impairment, Physical Disability, and Chronic Conditions on the Association of Sleep Duration with All-Cause Mortality Among the Very Old” said this is not the only factor.

“A possible explanation is that poor quality of sleep, such as sleep fragmentation, waking after sleep onset, sleep latency, and feelings of fatigue and lethargy after a long sleep may induce sleep extension and decrease resistance to disease,” researchers said. This, in turn, may lead to increased mortality.

The authors collected sleep data on nearly 20,000 Chinese adults between the ages of 80 and 105 for up to 10 years. They uncovered a relationship between longer periods of sleep (more than nine hours per night) and mortality, with a significant relationship between longer sleep and cognitive impairment on mortality.

However, the risk of death did not differ much for people with various physical disabilities and chronic conditions.

“These findings suggest that health practitioners and families should be aware of the potential adverse prognosis associated with long sleep,” the authors said. While getting a full night’s sleep is important for older adults and can contribute to health and quality of life, poor sleep—whether too much or too little—should be considered a red flag worth reporting to the physician or other practitioner. This is particularly true for older adults with cognitive impairment.

This study was conducted by researchers at the School of Public Health, Tianjin Medical University, Tianjin, P.R. China; Aging Research Center, Department of Neurobiology, Care Sciences and Society, Karolinksa Institute and Stockholm University; and Department of Biostatisticians, School of Public Health, Yale University, New Haven, Conn.

Click here for more information on the findings.