Catching a few z’s lasting longer than 30 minutes throughout the day is linked to adverse health effects.

Many people have the habit of taking afternoon naps. While a short nap can help restore energy and improve work efficiency, napping too long can make one feel groggy and more fatigued. Recent research has found that excessive napping can cause long-term harm, such as increasing the risk of cardiovascular disease, Alzheimer’s disease, and death.

According to 2022 survey data from the National Sleep Foundation, 30.5 percent of adults in the United States take afternoon naps more than once per week. Additionally, 42.7 percent of full-time workers regularly nap during their workday breaks.

Previous studies on the long-term health effects of napping have primarily focused on its benefits, such as promoting brain health and improving cognitive function. However, some of these studies did not account for the duration of naps, leading to limitations in their conclusions. Although there is still debate about the impact of nap duration on health and the optimal nap duration, many studies suggest that keeping naps under 30 minutes can enhance their benefits while reducing the potential adverse effects of longer naps.

The Vicious Cycle Between Long Naps and Alzheimer’s

The longer and more frequent the naps in older adults, the higher their risk of developing Alzheimer’s disease. Conversely, as Alzheimer’s symptoms worsen, nap duration and frequency tend to increase. This suggests a bidirectional relationship between excessive napping and Alzheimer’s. In a press release, researchers described this as a “vicious cycle,” a conclusion drawn from a 2022 study conducted by Harvard Medical School.

The researchers conducted a 14-year follow-up study on 1,401 participants (average age of 81) from the Rush Memory and Aging Project. The results indicated that the relationship between Alzheimer’s dementia and excessive napping appears to be bidirectional: Excessive napping (longer or more frequent naps) was associated with cognitive decline a year later, and cognitive decline was linked to more excessive napping the following year.

The study also found that older adults who napped for more than an hour each day had a 40 percent higher risk of developing Alzheimer’s disease compared to those with stable cognitive function.

Dr. Aron Buchman, a co-author of the study and a neurologist at Rush University Medical Center, emphasized in a press release that this was an observational study. Therefore, it cannot be concluded that napping causes Alzheimer’s disease or vice versa. However, it can be confirmed that “they unfold at the same time, and it’s possible that the same pathologies may contribute to both.”

Alzheimer’s disease is caused by the buildup of two proteins in the brain: amyloid beta and tau. While cognitive decline is the most recognizable symptom, these proteins can accumulate in various parts of the brain, brainstem, and spinal cord, leading to a range of symptoms. The researchers suggest that a persistent increase in the frequency and duration of daytime naps could be one of these symptoms.

Another study conducted by the University of California–Los Angeles, which tracked the cognitive abilities of 2,751 community-dwelling older men over 12 years, found that those who napped for 120 minutes or more each day had a 66 percent higher likelihood of developing cognitive impairment compared to those who napped for less than 30 minutes daily.

Excessive Napping Increases Cardiovascular Disease Risk

In recent years, more attention has been paid to the impact of nap duration on cardiovascular disease, with many studies using 30 minutes as the cutoff for defining nap duration.

A 2022 study involving 12,000 older people in Sweden found that compared to those who never nap, individuals who nap for 30 minutes had an 11 percent higher risk of cardiovascular disease. If the nap duration exceeds 30 minutes, the risk increases to 23 percent. Particularly, individuals who sleep less at night (less than seven hours) but nap for longer durations (more than 30 minutes) had the highest risk of cardiovascular disease—47 percent higher than those with optimal sleep duration (seven to nine hours) who do not nap.

In a press release, Weili Xu, the lead author and a senior researcher at the Karolinska Institutet in Sweden, emphasized that “even if sleep is lost during the night, excessive napping is not suggested during the day.”

In addition to cardiovascular diseases, dedicated studies on the effects of napping on atrial fibrillation and heart failure have also reached similar conclusions.

A 2023 study presented at the European Society of Cardiology Preventive Cardiology 2023 session involving nearly 20,000 middle-aged individuals (average age of 38) in Spain over almost 14 years indicated that people who nap for 30 minutes or longer had a 90 percent higher risk of developing atrial fibrillation (a type of heart arrhythmia) compared to those who nap for less than 30 minutes. Heart arrhythmia can, in turn, increase the risk of stroke and heart failure.

A study conducted by Harvard University in 2021, with a 14-year follow-up period, examined 1,140 community-dwelling older adults (average age of 80.7 years) and found a positive correlation between nap duration and frequency and the risk of heart failure. Individuals who napped for longer than 44.4 minutes (with 43 minutes being the average nap duration for Americans over 55) had a 1.73 times higher risk of heart failure compared to those who napped for less. Additionally, those who napped frequently each day (more than 1.7 times per day) had a 2.2 times higher risk of heart failure compared to those who napped less frequently (less than 1.7 times per day).

Compared to those who nap for less than 30 minutes per day, individuals who nap for 30 to 60 minutes and those who nap for more than 60 minutes had a 68 percent and 111 percent higher risk of heart failure, respectively.

A 2023 study on risk factors for cardiovascular disease, including metabolic syndrome and obesity, showed that excessive napping significantly increases the risk of these conditions.

The study, which focused on 3,275 adults from a Mediterranean population, indicated that those who regularly napped for 30 minutes or less had a 21 percent lower likelihood of developing high blood pressure. In contrast, individuals who napped for more than 30 minutes had a 41 percent higher chance of developing obesity and metabolic syndrome (characterized by higher values of blood pressure, blood sugar, waist circumference, body mass index, and weight) compared to those who napped for less than 30 minutes. Metabolic syndrome and obesity, in turn, increase the risk of heart disease, stroke, and Type 2 diabetes.

Excessive Napping Linked to Higher Mortality Risk

Early research has yielded contradictory results regarding the relationship between napping and all-cause mortality in older adults, possibly due to an insufficient focus on nap duration. A 2014 study tracked over 16,000 people in the United Kingdom for 13 years and found a correlation between nap duration and increased all-cause mortality risk. Specifically, napping for less than one hour per day was associated with a 14 percent increase in all-cause mortality, while napping for one hour or longer was associated with a 32 percent increase. Notably, the association between napping and death from respiratory diseases was more pronounced, with a 40 percent increase in mortality risk for those napping less than one hour and a 156 percent increase for those napping one hour or longer.

The researchers highlighted that the association between napping and all-cause mortality was particularly evident in individuals under 66 years old. Additionally, this association persisted even among those without preexisting health conditions.

Another meta-analysis from 2014 also found a positive linear relationship between nap duration and all-cause mortality. By employing a one-hour threshold, this study revealed that napping for more than one hour was linked with a 27 percent increase in all-cause mortality risk, whereas shorter naps did not exhibit this correlation.

The Optimal Nap Duration for Maximum Benefits

Short naps have been shown to offer benefits such as reducing fatigue, improving memory, and enhancing alertness while also benefiting brain and cardiovascular health. So how long should a nap be? As suggested by the National Sleep Foundation and the American Heart Association, the optimal duration is 20 minutes, with a maximum of 30 minutes.

Dr. Abhinav Singh, a member of the Sleep Foundation’s medical review panel and the medical director of the Indiana Sleep Center, explained that a 20- to 30-minute nap, known as a “power nap,” neither plunges individuals into a deep sleep that makes waking up difficult nor leaves them feeling groggy after being awakened. Instead, it gives a nice boost of energy.

A 2020 meta-analysis found a J-curve relationship between nap duration and the risk of incident cardiovascular disease, with the optimal nap duration being 25 minutes. Dr. Jesus Diaz-Gutierrez, the author of the study from Spain, also suggested, “Our study indicates that snoozes during the day should be limited to less than 30 minutes,” adding that “the optimal napping duration is 15 to 30 minutes.”

The National Sleep Foundation also recommends napping between 1 and 3 p.m., as this time coincides with the natural dip in alertness many people experience after lunch, which is related to our circadian rhythms. Taking a short nap during this time can help alleviate afternoon drowsiness.

Important Notice: This article was originally published at www.theepochtimes.com by Ellen Wan where all credits are due.

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