Older men who regularly take long daytime naps may want to pay attention to their brain health, according to striking research published in Alzheimers & Dementia.

Scientists at renowned research institutions tracked the sleep habits and cognitive function of thousands of older men for more than a decade, uncovering an unmistakable link between lengthy naps and a higher risk of cognitive decline over time. This isn’t just another story about sleep. It’s a wake-up call about the subtle signals our bodies might send before memory problems or dementia emerge.

The study zeroed in on over 2,700 men aged 65 and above, living independently. Researchers used a clever device—a wrist actigraph—to objectively measure periods of inactivity, which reliably signalled actual sleep rather than just moments of rest with eyes closed. Forget self-reports or patchy memory about napping habits; this was sleep science at its most precise. Participants wore the device for several days, providing robust data on daily nap patterns. Their thinking skills were tested multiple times over twelve years.

The findings? Men who napped for at least two hours each day were significantly more likely to experience cognitive impairment as they aged. In fact, their odds were 66 percent higher compared to peers who napped for less than half an hour.

This was no fluke. The association held firm even when scientists considered other factors—age, education, health history, depression, physical activity, smoking habits, use of sleep medicines, as well as the quality and quantity of their night-time sleep.

What’s more, this connection didn’t waver when experts accounted for sleep apnoea and other breathing problems at night. Long daytime napping emerged as a strong predictor of future memory and thinking trouble. It’s a finding that has potential implications for anyone caring for older relatives, as well as for doctors and nurses monitoring patients’ overall health.

The study’s design deserves attention. Instead of relying on subjective reports—how sleepy someone feels during the day or what they recall about their nap schedule—this research tapped into hard data. The actigraph recorded every minute of movement (or lack thereof), giving scientists an accurate picture of true nap duration. This approach cuts through the fog that often surrounds sleep studies in older adults, who may forget or misreport their habits.

Over the course of twelve years, researchers tracked two key aspects of cognition: global thinking skills (measured by the Modified Mini-Mental State exam) and executive function (tested by the Trail Making Test Part B). These tests are well-established in medical research; they check memory, orientation, attention, processing speed and the ability to adapt to new tasks.

The results painted a clear picture. Men who took longer naps experienced more dramatic drops in their cognitive scores. The steepest declines were seen in those napping two hours or more each day. Executive function also suffered, with slower completion times on complex tasks.

But here’s where things get even more interesting: the impact of napping seemed to depend on how well participants slept at night. Among those with decent night-time sleep—between six and eight hours, with good sleep efficiency—long naps spelled bigger trouble for their future cognitive health. For men with poor night-time sleep or those sleeping too little or too much at night, lengthy daytime naps weren’t linked to increased risk.

What does this mean? Napping might be compensatory in those who struggle to sleep overnight. If your night is filled with tossing and turning or frequent waking, grabbing some extra shut-eye during the day could help keep your thinking sharp. But if you’re sleeping soundly at night and still dozing off for hours during the day, it may be time to ask why.

Science offers several possible explanations for the link between long naps and brain decline. Some researchers point to disruptions in circadian rhythms—the body’s natural clock that governs the sleep-wake cycle. Frequent daytime sleeping can throw off these rhythms, which has been connected to neurodegenerative conditions in previous studies.

Others highlight vascular and metabolic factors. Studies have shown links between daytime napping and higher risks of diabetes, heart disease and inflammation. All these conditions can harm small blood vessels in the brain or trigger processes that speed up cognitive decline.

Another idea involves sleep inertia—the grogginess and mental sluggishness that can follow waking from deep sleep. Longer naps often mean waking from deeper stages of sleep, increasing the chances of persistent cognitive fog after rising.

Some experts suggest a genetic predisposition towards excessive sleepiness and prolonged napping may overlap with vulnerabilities in brain health. In these cases, lengthy naps could be both a symptom and a marker of underlying changes in the nervous system.

What should you do with this information? For older adults and their families, paying attention to nap habits is wise. A short nap after lunch—ten to thirty minutes—can refresh you without interfering with night-time rest. But if you regularly find yourself sleeping for two hours or more during the day, especially when your night-time sleep seems adequate, consider discussing it with your GP.

Clinicians can use nap patterns as part of routine health assessments in older patients. Tracking changes over time—gradual increases in nap length or frequency—may offer early clues about shifts in cognitive function or underlying medical conditions.

It’s not just about memory loss or dementia. Long naps can signal changes in mood, medication effects, pain levels or other health issues that deserve attention. By sharing details about daily routines—including nap timing and length—patients help build a fuller picture for healthcare providers.

The study’s strengths stand out. Its large sample size, objective sleep measurement and repeated cognitive assessments make its findings compelling. Adjusting for a wide range of confounding factors lends credibility to the results.

Yet limitations remain. The participants were mostly older men living independently; results might not fully apply to women, younger people or those in different settings. The actigraph measures inactivity rather than brain waves; while it closely matches actual sleep, it can sometimes misclassify periods of quiet wakefulness as naps—especially in very sedentary individuals.

Researchers didn’t diagnose specific types of dementia or pinpoint exactly when cognitive impairment started. Instead, they used robust criteria—diagnosis by a doctor, confirmed use of Alzheimer’s medications and significant drops in cognitive test scores—to define clinically meaningful decline.

Categories for night-time sleep duration and efficiency reflected the reality of older men’s typical sleep patterns; they may not apply elsewhere. The study focused on total daily nap duration but didn’t tease apart whether frequent short naps differ from one long nap in terms of brain impact.

Experts at leading institutions call this study a milestone in understanding how sleep habits relate to ageing brains. They emphasise that daytime naps aren’t inherently harmful—short naps can sharpen alertness and mood—but persistent long naps deserve attention as a possible warning sign.

For carers watching loved ones age, this research offers guidance: keep an eye out for changes in sleep routines. Is grandad suddenly spending more time asleep during daylight hours? Did his nap habit shift from brief dozes to marathon afternoon slumbers? These changes can spark important conversations about health and wellbeing.

For clinicians, the message is clear: ask about nap patterns as part of routine checks. Combine this information with details on night-time sleep quality, mood, medication and physical health to guide next steps.

Always be mindful but not alarmed. A short siesta is perfectly normal—and may even have benefits for alertness and mood. But if you notice your daytime naps stretching longer and longer without clear reason, especially alongside good night-time rest, don’t ignore it.

Future research will look at whether nap frequency and timing play roles distinct from total duration. Scientists hope to unravel biological mechanisms linking sleep behaviour with brain changes—circadian rhythms, inflammation, amyloid build-up and vascular damage are all under scrutiny.

Wearable devices make it easier than ever to track sleep patterns objectively. As technology becomes part of our daily lives, simple measures like nap length could help spot risks early—long before more serious symptoms appear.

This study shines a spotlight on a simple behaviour that could hold clues to brain health years before problems surface. Long daytime naps—especially two hours or more—may signal higher risk for cognitive decline in older men who otherwise sleep well at night. The findings underscore the importance of viewing sleep holistically—not just focusing on hours spent in bed after dark but considering total daily sleep patterns.

Caring for our brains means paying attention to these subtle signals. Take note of changes, talk openly with healthcare providers and use new technologies wisely. With vigilance and awareness, we can catch warning signs early and support healthy ageing for ourselves and those we love.