Dementia symptoms peak in winter and spring, study finds

Adults both with and without Alzheimer's disease have better cognition skills in the late summer and early fall than in the winter and spring, according to a new study published this week in PLOS Medicine by Andrew Lim of Sunnybrook Health Sciences Centre and the University of Toronto, Canada, and colleagues.

There have been few previous studies concerning the association between season and cognition in older adults. In the new work, researchers analyzed data on 3,353 people enrolled in three different cohort studies in the U.S., Canada, and France. Participants had undergone neuropsychological testing and, for some participants, levels of proteins and genes associated with Alzheimer's disease were available.

The authors found that average cognitive functioning was higher in the summer and fall than the winter and spring, equivalent in cognitive effect to 4.8 years difference in age-related decline. In addition, the odds of meeting the diagnostic criteria for mild cognitive impairment or dementia were higher in the winter and spring (odds ratio 1.31, 95% CI: 1.10-1.57) than summer or fall. The association between season and cognitive function remained significant even when the data was controlled for potential confounders, including depression, sleep, physical activity, and thyroid status. Finally, an association with seasonality was also seen in levels of Alzheimer's-related proteins and genes in cerebrospinal fluid and the brain. However, the study was limited by the fact that each participant was only assessed once per annual cycle, and only included data on individuals from temperate northern-hemisphere regions, not from southern-hemisphere or equatorial regions.

"There may be value in increasing dementia-related clinical resources in the winter and early spring when symptoms are likely to be most pronounced," the authors say. "By shedding light on the mechanisms underlying the seasonal improvement in cognition in the summer and early fall, these findings also open the door to new avenues of treatment for Alzheimer's disease."

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Peer-reviewed / Meta-analysis / People

Research Article

Funding:

This study was funded by National Institutes of Health (http://www.nih.gov; P30AG10161, R01AG052488, R01AG043379, R01AG15819, R01AG17917, R01AG36042, R01AG36836, U01AG046152, RF1AG022018, R01AG042210, and R01NS078009); Canadian Institutes of Health Research (http://www.cihr-irsc.gc.ca/; MOP125934, and MSH136642); Alzheimer's Association (http://www.alz.org) and Brain Canada (http://www.braincanada.ca; AARG501466); National Sciences and Engineering Research Council of Canada (http://www.nserc-crsng.gc.ca; RGPIN-2017-0692); Agence Nationale de la Recherche (http://www.agence-nationale-recherche.fr; MALZ grant 2013); Agence Publique Hopitaux de Paris (http://fondationrechercheaphp.fr/); Institut National de la Sante et de la Recherche Medicale (http://www.inserm.fr/en); the Illinois Department of Public Health (http://www.dph.illinois.gov/); the Alzheimer Society of Canada (alzheimer.ca/); the Heart and Stroke Foundation of Canada (http://www.heartandstroke.ca/); and the Robert C. Borwell Endowment Fund. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interests:

I have read the journal's policy and the authors of this manuscript have the following competing interests: SEB has ad-hoc consultancies with the following: GE Healthcare, Boehringer Ingelheim, Novartis, Merck, Eli Lilly, Pfizer. Continuing medical education from: Novartis, Eisai, Medscape/Biogen, Eli Lilly. SEB receives grants to her institution from: Elan, Roche, GE Healthcare, Eli Lilly, Pfizer, Lundbeck, Transition Therapeutics, Biogen Idec, Novartis, Genentech, and Optina. CP is a consultant for FUJIRIBIO laboratory.

Citation:

Lim ASP, Gaiteri C, Yu L, Sohail S, Swardfager W, Tasaki S, et al. (2018) Seasonal plasticity of cognition and related biological measures in adults with and without Alzheimer disease: Analysis of multiple cohorts. PLoS Med 15(9): e1002647. https://doi.org/10.1371/journal.pmed.1002647

Image Credit: Staff Sgt. Jason McCasland, U.S. Air Force

Author Affiliations:

Division of Neurology, Department of Medicine, Hurvitz Brain Sciences Program, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada

Rush Alzheimer Disease Center, Rush University Medical Center, Chicago, Illinois, United States of America

Department of Neurological Sciences, Rush University, Chicago, Illinois, United States of America

Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario, Canada

Centre de Neurologie Cognitive, Hôpitaux Saint-Louis Lariboisière Fernand-Widal, Assistance Publique-Hôpitaux de Paris, University of Paris Diderot, Paris, France

Inserm U942, Paris, France

Department of Behavioral Sciences, Rush University Medical Center, Chicago, Illinois, United States of America

Center for Translational & Computational Neuroimmunology, Department of Neurology, Columbia University Medical Center, New York, New York, United States of America

In your coverage please use this URL to provide access to the freely available paper:

http://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1002647