4 Features of Summer That Cloud Your Thinking |
Summertime conditions can impair memory, thinking, and concentration.
These effects are driven by sleep disruption, heat, dehydration, and smoke exposure.
Awareness and simple habits can help protect cognitive performance.
As summer approaches, you may find yourself forgetting things, struggling to concentrate, or generally feeling cognitively slower. You may wonder, “Is this normal? Does this happen to everyone?”
In past summers, this has certainly happened to me. For instance, I’ve struggled with more tip-of-the-tongue words than usual. The ever-elusive names—but also common words. Words like…what do you call that thing you put on the dog? Not a collar—the one with four straps?(Two minutes later): Harness.
Is there something about the summer months that causes worse brain fog and a sluggish memory?
Research shows the answer is yes. In fact, scientists have identified four key factors. And, fortunately, if you’re aware of these harmful conditions, you can mitigate their effects.
Feature #1. Longer Days—And Shorter Nights
Our brains require a steady diet of quality sleep to perform optimally.
But some research has shown that sleep suffers in the summertime. A study done in the Netherlands revealed that sleep duration—measured objectively with wrist-worn activity monitors—was shorter in summer than winter.
In another study, researchers in Germany examined brain activity during sleep across 12 months of the year. Although they found that overall time asleep did not change across seasons, REM sleep did. In this study, REM sleep was reduced in spring and early summer and increased during the winter months.
And the REM periods of sleep are known to be important for some memory and thinking skills, such as consolidating emotional memories in long-term memory.
What’s causing poor sleep in the summer? A major determinant seems to be extended daylight.
For example, a study conducted in the Arctic summer—with some periods of 24-hour sunlight—showed that extremely long daylight was associated with disrupted circadian rhythms, delays in melatonin secretion onset, and worse sleep.
Feature #2. Hotter Temperatures
Here’s a sentence I never envisioned writing: Maybe Mel Tormé was right: It’s just tooooo darn hot.
Do sweltering temperatures also diminish our thinking abilities?
A group of scientists in the UK investigated this. They brought volunteers into the lab to measure their mental agility in two thermal conditions: room temperature (70 °F) and an oppressively hot environment (103 °F).
In the heat, participants showed worse performance on a computer task that required inhibitory control—the ability to ignore distractions and stay focused. That’s an ability we often take for granted—yet we rely on it constantly in daily life.
More broadly, studies show that high temperatures impair both simple and complex cognitive tasks. However, it’s much worse when doing something more demanding—activities like doing mental arithmetic, planning how to solve a problem, and driving.
Feature #3. Dehydration
Another factor in summer’s assault on thinking is dehydration. Summer brings two key risks: the aforementioned hotter temperatures and greater physical activity.
Abundant evidence shows that dehydration impairs cognition. And importantly, the drop in performance is more extreme in high-level cognitive tasks, such as those measuring attention or logical reasoning, compared to low-level tasks, such as a simple reaction time measure.
The good news is that rehydrating with water reverses dehydration-associated dips in cognitive function, including performance on memory and cognitive flexibility tasks.
Feature #4. Wildfire Smoke
I live in the Pacific Northwest. Here, as in many places, our summers are getting increasingly smoky from wildfires.
I personally seem to have more headaches on really smoky days, and I wondered if these pollutants were affecting my brain and thinking.
Unfortunately, they probably are. A recent review showed that our brains are impacted by extreme heat, wildfire smoke, and the combination of the two. Specifically, these conditions are associated with inflammation in the brain and disruptions in neuronal signaling (the basis of all thinking).
For example, Cleland and colleagues documented a link between smoke levels and reduced focused attention. They followed a large group of people for a year, tracking their scores on a test of selective attention and smoke levels. The two measures matched up. As concentrations of wildfire smoke and particulates went up, focused attention scores went down.
Maybe we’d better step up those Smokey Bear ads again.
Of course, your specific countermeasures to summer’s harmful effects on thinking will depend on where you live and your lifestyle variables (to some degree—no pun intended). But here is a buffet of advice to choose from.
Protect your sleep. Even if you live near the Arctic Circle, you can use blackout curtains or eye masks to create fake dark nights.
Stay cool. Use A/C or fans, limit outdoor time, and avoid physical activity during the blazing hot hours (isn’t it great to hear advice to exercise less?)
Stay hydrated. Your goal should be light-to-clear colored urine. That’s not a very scientific-sounding test, but it works without having to factor in multiple variables.
Minimize smoke exposure. Tips for this include using A/C and avoiding outdoor physical activity when air quality is poor. See CDC safety guidelines on wildfire smoke.
And, as a scientist, I can’t help but mention one piece of advice for a broader, long-term solution for you and your fellow Earth inhabitants: Act to reduce global warming (a main source of hotter temperatures and increased wildfires). Remember that every little bit you can do helps.
Copyright Suzanna Penningroth
An article similar to this was published on the Psychological Science Lite blog: Blog - S. L. Penningroth
Centers for Disease Control and Prevention. (2024, April 15). Safety guidelines: Wildfires and wildfire smoke. U.S. Department of Health and Human Services.https://www.cdc.gov/wildfires/safety/how-to-safely-stay-safe-during-a-wildfire.html
Cleland, S. E., Wyatt, L. H., Wei, L., Paul, N., Serre, M. L., West, J. J., Henderson, S. B., & Rappold, A. G. (2022). Short-term exposure to wildfire smoke and PM2.5 and cognitive performance in a brain-training game: A longitudinal study of U.S. adults. Environmental Health Perspectives, 130(6), Article 067006. https://pmc.ncbi.nlm.nih.gov/articles/PMC9196888/pdf/ehp10498.pdf
Garriga, A., Sempere-Rubio, N., Molina-Prados, M. J., & Faubel, R. (2022). Impact of seasonality on physical activity: A systematic review. International Journal of Environmental Research and Public Health, 19(1), Article 2. https://doi.org/10.3390/ijerph19010002
Malcolm, R. A., Cooper, S., Folland, J. P., Tyler, C. J., & Sunderland, C. (2018). Passive heat exposure alters perception and executive function. Frontiers in Physiology, 9, Article 585. https://doi.org/10.3389/fphys.2018.00585
Paul, M. A., Love, R. J., Hawton, A., Brett, K., McCreary, D. R., & Arendt, J. (2015). Sleep deficits in the High Arctic summer in relation to light exposure and behaviour: use of melatonin as a countermeasure. Sleep Medicine, 16(3), 406-413. https://www.sciencedirect.com/science/article/abs/pii/S1389945715000398
Seidler, A., Weihrich, K. S., Bes, F., de Zeeuw, J., & Kunz, D. (2023). Seasonality of human sleep: Polysomnographic data of a neuropsychiatric sleep clinic. Frontiers in Neuroscience, 17, Article 1105233. https://doi.org/10.3389/fnins.2023.1105233
Stachenfeld, N. S., Leone, C. A., Mitchell, E. S., Freese, E., & Harkness, L. (2018). Water intake reverses dehydration-associated impaired executive function in healthy young women. Physiology & Behavior, 185, 103–111. https://doi.org/10.1016/j.physbeh.2017.12.028
Taylor, L., Watkins, S. L., Marshall, H., Dascombe, B. J., & Foster, J. (2016). The impact of different environmental conditions on cognitive function: A focused review. Frontiers in Physiology, 6, Article 372. https://doi.org/10.3389/fphys.2015.00372
Walker, M. P. & van der Helm, E. (2009). Overnight therapy? The role of sleep in emotional brain processing. Psychological Bulletin, 135(5), 731–748. https://doi.org/10.1037/a0016570
Walker, M. P. (2009). The role of sleep in cognition and emotion. Annals of the New York Academy of Sciences, 1156(1), 168–197. https://doi.org/10.1111/j.1749-6632.2009.04416.x
White, A. R. (2024). The firestorm within: A narrative review of extreme heat and wildfire smoke effects on brain health. Science of the Total Environment, 922, Article 171239.https://doi.org/10.1016/j.scitotenv.2024.171239
Wittbrodt, M. T., & Millard-Stafford, M. (2018). Dehydration impairs cognitive performance: A meta-analysis. Medicine & Science in Sports & Exercise, 50(11), 2360–2368. https://doi.org/10.1249/MSS.0000000000001682
Xu, R., Yu, P., Abramson, M.J., Johnston, F.H., Samet, J.M., Bell, M.L., Haines, A., Ebi, K.L., Li, S., & Guo, Y. (2020). Wildfires, global climate change, and human health. New England Journal of Medicine, 383(22), 2173-2181. https://www.nejm.org/doi/pdf/10.1056/NEJMsr2028985
Zerbini, G., Winnebeck, E. C., & Merrow, M. (2021). Weekly, seasonal, and chronotype‐dependent variation of dim‐light melatonin onset. Journal of Pineal Research, 70(3), e12723. https://onlinelibrary.wiley.com/doi/pdf/10.1111/jpi.12723
There was a problem adding your email address. Please try again.
By submitting your information you agree to the Psychology Today Terms & Conditions and Privacy Policy