Nov. 13 2020

Cool Temperatures May Blunt Cognition in Older Adults

It’s well known that older adults are more apt to feel chilly. New research finds that cooler temperatures may do more than cause discomfort. Columbia University Mailman School of Public Health researchers find that lower temperatures are associated with an elevated risk of impaired cognition among individuals age 84 and older. This relationship is further heightened in individuals with damaged mitochondrial DNA, a sign that these cellular powerplants play a role in adaptation to ambient temperature.

Study results appear in the journal Environmental Epidemiology.

Researchers analyzed data collected from 591 Boston-based men enrolled in the Veterans Affairs’ Normative Aging Study between 2000 and 2013. Cognitive function was evaluated via the Mini-Mental State Examination. Outdoor temperature was estimated at residential addresses one day before the examination using a validated temperature model. Mitochondrial DNA copy number (mtDNAcn), a representation of the mitochondria’s response to oxidative stress as well as general dysfunction, was determined through an analysis of blood samples.

In individuals age 84 or older, a 1°C decrease in temperature (1.8°F) was associated with 35 percent increased odds of cognitive impairment. These odds were higher among individuals with lower mtDNAcn, suggesting that healthy mitochondria may help people adapt to lower outdoor temperatures. Future research could shed more light on biological mechanisms of age-related declines in the body’s ability to regulate response to outside stressors.

“General cognitive function deteriorates with aging, a change that has been linked to outdoor temperature. Older individuals have reduced ability to adapt to changes in outdoor temperature than younger people,” the authors write. “Colder temperature causes vasoconstriction and this decreased blood flow may be related to worse cognitive function. In older individuals, this may be compounded by an already weakened vascular system.”

The study’s first author is Jacopo Dolcini, MD, PhD, a researcher in the Department of Environmental Health Sciences at Columbia Mailman School. The senior author is Andrea Baccarelli, MD, PhD, chair of Environmental Health Sciences at Columbia Mailman School. Co-authors are affiliated with Columbia Mailman; Polytechnic University of Marche, Ancona, Italy; Harvard T.H. Chan School of Public Health; and Boston University School of Medicine. A full list of authors is published in the study.

The research was supported by the National Institutes of Health (grants ES015172, ES021895, ES028472, ES021733, ES025225, ES027747, ES021357, ES009089, ES000002) and by the U.S. Environmental Protection Agency (RD-83479801).

Cooler Temperatures Linked to Sedentary Behavior in Children

Outdoor temperatures don’t just affect the health of older people. Even at the youngest ages, temperature variations matter, albeit in a different way. A separate study published in the journal PLoS One finds that warmer temperatures, as well as greater diurnal temperature variation, are linked to greater levels of physical activity among 4–to-6-year-old children in Mexico City.

The researchers find that these children have on average 0.26 percent less daily sedentary time (approximately 2.2 minutes) for each 1°C increase in ambient maximum temperature, 0.27 percent less daily sedentary time (approximately 2.3 minutes) for each 1°C increase in ambient mean temperature, and 0.23 percent less daily sedentary time (approximately 2.0 minutes) for each 1°C increase in diurnal variation. However, the researchers caution that their study doesn’t capture the effects of extreme heat, which would likely reverse the trend.

“Sedentary behavior is a worldwide public health concern. There is consistent and growing evidence linking sedentary behavior to mortality and morbidity,” the authors write. “Our results demonstrate that children in Mexico City are more likely to be active in warmer weather which suggests a need for interventions that discourage sedentary behavior when it is cooler outside.”

The study was led by Sandy Wong at the Ican School of Medicine at Mount Sinai. Andrea Baccarelli is a co-author. A full list of co-authors and their affiliations is published in the study. This research was supported by the National Institutes of Health (grants ES013744, ES014930, ES021357, ES028522, ES023515, HD049311, ES023450).