Memory and concentration peak in the late summer for adults in their 70s, 80s, and 90s according to a new study co-led by Columbia neurologist Philip De Jager, MD, PhD, published September 4 in PLOS Medicine. The findings suggest that cognitive function in older adults varies over the course of the year as the seasons change, even among those who have Alzheimer’s disease.

Further research to understand the mechanism by which these seasonal changes occur may lead to new ways to treat memory loss and improve cognitive performance in patients with Alzheimer’s disease.

Why do this study?

“We had previously discovered that the change in seasons causes large-scale alterations in the nucleus and function of brain cells in older individuals,” says De Jager, who is the Weil-Granat Professor of Neurology at Columbia University Vagelos College of Physicians and Surgeons.

“We hypothesized that, if brain cell function was changing so much, cognitive function, which is the expression of brain cell function, might also be affected by seasonal rhythms.”

How was the study conducted?

The study looked at more than 3,300 older adults from multiple ethnic groups living in the United States, Canada, and France.

Participants had annual evaluations that included 19 different cognitive tests—measuring, for example, working memory, perceptual speed, and visuospatial ability. The scores were averaged to create a composite cognitive score.

The researchers also looked for seasonal variations in gene activity and in diagnoses of mild cognitive impairment (MCI), Alzheimer’s, and dementia.

What did the study find?

Among older adults, cognitive performance peaked just before the fall equinox (this year, Sept. 22 in the Northern Hemisphere) and reached a low point near the spring equinox. The effect was strongest for working memory and perceptual speed.

“The seasonal difference is significant,” says De Jager. “Cognitive function normally declines with age, and the seasonal difference we found is roughly equivalent to 4 years of aging. This means that an older person functioned as if they were 4 years older in the winter, compared to how they functioned in the summer.”

The fluctuations were seen in both healthy adults and adults diagnosed with Alzheimer’s, though seasonal differences were smaller in those with dementia.

The effect did not change when other factors that can influence cognitive function were considered. These included symptoms of depression, self-reported hours of sleep and physical activity, and thyroid activity (measured by hormone levels).

What does the study mean?

The presence of robust seasonal variation in cognition among people with Alzheimer’s suggests that identifying the underlying mechanisms could lead to new ways to improve cognitive performance in dementia patients and in people at risk of cognitive decline.

The findings also suggest that Alzheimer’s patients may need more care in the winter and early spring than in the summer.

Seasonal changes in cognition may account for the observation that some individuals diagnosed with MCI can regain normal cognition when they are re-evaluated at a later date.

The study did not examine younger adults, but previous studies have not found any association between season and cognition. “We think that an abundance of cognitive reserve in younger adults may account for the age difference,” De Jager says.

What’s next?

This strong seasonal effect needs to be confirmed by larger studies, De Jager says.

In parallel, the researchers are looking for the molecules in the brain that are driving this seasonal effect, so that drugs could be developed to mimic the effect of improved cognitive performance in the summer. Exposure to light is another possible approach to modulate these changes in brain function, and, if true, phototherapy may be effective at maintaining peak cognition year-round.