Naps are one of life’s pleasures, but as we age, they can also be an early sign of health issues we’re unaware of. These findings are thanks to a groundbreaking study of more than 1,000 people who had their daytime naps tracked for up to 19 years.
Researchers from Mass General Brigham and Rush University Medical Center monitored 1,338 US adults aged 56 years or older for nearly two decades, investigating whether daytime sleeping – essentially, naps between 9 am and 7 pm – offered clues as to whether this behavior was a sign of underlying health conditions.
As someone crossing timezones often and who has a brain that’s far too active very late at night, I’ve grown to appreciate how restorative and important daytime naps are. So this new research doesn’t state – nor did it find – that naps in general are something to worry about. However, in a rare study covering such an extensive time period, it did find that certain napping habits could be early warning signs of serious issues that increase mortality risk quite significantly.
“Excessive napping later in life has been linked to neurodegeneration, cardiovascular diseases and even greater morbidity, but many of those findings rely on self-reported napping habits and leave out metrics like when and how regular those naps are,” said the study’s lead author Chenlu Gao, an investigator in the Department of Anesthesiology at Mass General Brigham, who also works in the Division of Sleep and Circadian Disorders in the Department of Medicine. “Our study is one of the first to show an association between objectively measured nap patterns and mortality and suggests there is immense clinical value in tracking napping patterns to catch health conditions early.”
One of the most difficult aspects of health research is being able to monitor a study population for a period of time that makes it real-wold relevant. So while this work is still observational, with unavoidable variables impacting individuals in the program, patterns emerged that haven’t been identified before. What’s more, even though the cohort selected for the study was limited (Illinois-based), the researchers made adjustments in order to represent the findings as robustly as possible – something difficult to manage over longitudinal human studies.
“We conducted four sensitivity analyses to ensure the results were not driven by (1) reverse causation (by excluding participants who died within two years after baseline); (2) nap outliers (by excluding participants napping >2 hours per day); (3) comorbidity burden (by excluding participants with >2 of the seven chronic conditions or taking >2 of the five medication categories at baseline); or (4) baseline cognitive impairment (by excluding participants with mild cognitive impairment or dementia at baseline), because cognitive impairment was associated with napping in our group’s prior work,” the team explained.
“Cognitive status was determined by 19 cognitive tests, neuropsychological review, and clinician diagnosis based on National Institute of Neurological and Communicative Disorders and Stroke and Alzheimer’s Disease and Related Disorders Association criteria.”
Essentially, the researchers found that people who had longer and more regular naps – particularly in the morning – had a higher mortality rate, even after all the adjustments were made to the data. Previously, daytime sleeping has been linked to a suite of health issues in older adults, but there’s been no substantial data that’s been able to narrow it down more than this broad hypothesis. And some studies have actually found the opposite – that naps have a positive impact on cognitive function. However, the time and duration of naps – not to mention the size and period of study – doesn’t make previous findings comparable.
Ultimately, each additional hour of daytime napping each day was associated with around 13% higher mortality risk, while every extra nap per day was linked to around a 7% higher mortality risk. Meanwhile, morning nappers had 30% higher mortality risk compared to afternoon snoozers. And one for us types who have no pattern with their naps, irregular sleeping had no statistically relevant impact on mortality risk.
And this is also not the first study to suggest daytime naps could be a red flag for early signs of cognitive decline seen in Alzheimer’s disease. But as with that 2022 research, the issue isn’t napping but when it becomes “excessive.” As to what excessive is, it’s unlikely we’ll be able to put a number of minutes or hours on that.
Nor should this research frame napping as something to avoid – after all, more than half of older adults (these scientists estimate it to be around 60% of people in 56 years and over age group in their study) take some kind of daytime snooze. The study points out that it’s not the nap itself that is the issue, but how underlying chronic conditions that may be undiagnosed can cause increased fatigue, resulting in longer daytime periods of sleeping.
“We found that older individuals with longer nap duration, more frequent naps, and a tendency to nap in the morning were at greater mortality risk over up to 19 years of follow-up,” they noted. “These findings suggest that excessive and morning napping may signal late-life vulnerability.
“Cardiovascular pathways are a possible mechanism linking excessive napping to mortality,” they suggested. “Sleep disruption and circadian misalignment, which may manifest as excessive napping, can lead to increased blood pressure, attenuated endothelial function, and heightened sympathetic activation. These changes in autonomic function and vascular system may create a proinflammatory and proatherogenic state that elevates the risk for fatal events. Consistently, past research has associated long daytime naps with cardiovascular risk factors (eg, obesity and high blood pressure) and cardiovascular diseases. Moreover, excessive daytime sleepiness may be caused by underlying sleep disorders such as obstructive sleep apnea, which is associated with greater cardiovascular events and mortality.
“Notably, our intermediate models demonstrated that the associations between napping and mortality remained significant even after accounting for nighttime sleep duration and quality,” they added. “These findings suggest that daytime napping is not merely a compensatory response to nocturnal sleep disruption but may serve as an independent marker for mortality risk.”
The research was published in the journal JAMA Network Open.
Source: Mass General Brigham