Alzheimer's disease Brain Featured Research

When do older adults do their best thinking? It depends on the season, study suggests

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Written by Jennifer Palisoc

Did you know that our brains change from season to season? Researchers have found that most people do their best thinking at a certain time of year.

Dr. Andrew Lim is the lead investigator of a recent study published in the journal PLOS Medicine, which looked at how cognitive function, thinking and memory, changes throughout the year in older adults with and without Alzheimer’s disease.

It is the result of more than 10 years of research at Alzheimer’s centres in Canada, the United States and France, where investigators looked at data from over 3,300 older adults, including thinking and memory tests, as well as information about gene expression.

Dr. Lim shares insight into the research that found there is a big difference in how people think from season to season.

What did your study find?

What we found was that in older adults with and without Alzheimer’s disease the ability to think and concentrate — their cognition — varies quite a bit from season to season.

Our study determined that participants performed quite a bit better in the fall compared to the spring. Cognition peaked around the fall equinox. The difference between fall and the spring was actually much larger than we’d expected; it was equivalent to almost four years of aging.

Someone who had the cognitive performance of an 80 year old in the spring would perform as though they were 76 years old, by the time fall emerged. It’s quite a significant effect on cognitive performance.

We found this pattern was the same for adults with and without Alzheimer’s disease — even those with Alzheimer’s would improve from the spring to the fall.

Why does the brain change season to season?

It seems there are biological changes that happen in the brain from season to season at the gene level and at the protein level that may be related to changes in cognition.

One of the potential contributors might be that levels of the Alzheimer’s disease proteins amyloid beta and tau in the spinal fluid vary from season to season.

We’re very interested in what could be driving that.

There has been some speculation in the field that it could be related to a change in activity levels throughout the year, sleep or vitamin D levels. Light exposure is another theory from the field, but in this study, the peak cognition was in the fall, rather than the summer when daylight is longest. All of these possibilities need more research.

So we’re interested in doing some follow-up studies and measuring these and trying to find out exactly what’s driving this because if we can figure that out, then we could potentially devise approaches to take that improvement that people get from the spring to the fall and make it last all year round and thereby shave four years of cognitive aging off of everyone.

Why is this important?

It has health systems implications for care delivery, it has implications for non-drug management of cognition, and implications for future drug development.

Knowing that people’s cognition worsens in the winter and spring, may allow us to reinforce health care resources at those times. It may be that there is a greater need for resources devoted to dementia care during the winter and spring when people are most vulnerable.

This may also mean that there could be a non-drug intervention that could impact people’s thinking and concentration. From a behavioural treatment perspective, this may be related to changing a person’s level of physical activity or environmental factors such as light exposure or from a nutritional perspective, the amount of vitamin D a person receives. All of these possibilities need to be studied further.

We’re also interested in better understanding the genes and the proteins that are driving this, which may allow us to eventually develop drugs that can target these proteins and improve cognition.

What is important for families to take away from this study?

It’s important to know that the brain of a person with Alzheimer’s continues to change throughout the year. Cognitive change isn’t a one-way street – it isn’t a one-way trip down hill. Instead, cognition is changeable, even in patients with Alzheimer’s disease, and one or more seasonal factors are capable of driving dramatic cognitive improvement each year.

It isn’t that there’s so much damage that nothing can be done– something is happening across the seasons, that every year takes some of that damage and reverses it.

Finally, It’s important to recognize that the winter and spring may be accompanied by a temporary worsening of cognition and that family members or caregivers of individuals with Alzheimer’s disease may need to provide support at these times, while retaining hope that some of this may reverse by fall.

About the author

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Jennifer Palisoc

Jennifer Palisoc is a Communications Advisor at Sunnybrook.

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