Getting enough sleep has long been considered one of the cornerstones of good health. While many health experts recommend around eight hours of rest each night, new research suggests that the ideal amount of sleep may actually be lower for some people. A long-term study has found that women who slept between five and six-and-a-half hours a night were the most likely to survive over a 14-year period, raising fresh questions about widely accepted sleep guidelines.

Debunking the Eight-Hour Sleep Myth

For decades, health advice has constantly stressed that adults will function properly if they sleep at least 8 hours at night on regular basis. However, a growing body of scientific research suggests the optimal amount of sleep may vary for different people, with different lifestyle and preferences, and this may even be lower than what is a long-held traditional belief about the recommended sleep duration.

A long-term study led by researchers at the University of California San Diego has challenged this widely accepted guideline. According to the findings, women who slept regularly at night between five and six-and-a-half hours per night showed excellent survival rates over a significant period of fourteen years.

The research adds an important point to a broader scientific debate about how much sleep people actually need and whether sleeping consistently for a longer duration is one of the primary reasons for maintaining better health.

Tracking Sleep Over More Than a Decade

The study followed 444 middle-aged and elderly women from San Diego who participated in a large observational health project. Their average age at the beginning of the research was around 67 years.

Researchers actively and vigilantly monitored the sleep patterns of the participants using wrist-worn activity monitors known as actigraphs. These devices track movement to precisely estimate when someone is asleep or awake during the most important night-time sleep.

Participants properly wore the monitors for a week during the initial phase of the study, which allowed the researchers to objectively measure their sleep pattern instead of relying on a less precise self-reported estimate. The participants were then tracked for a period of more than a decade to determine long-term survival outcomes.

Five to Six-and-a-Half Hours of Night Sleep Linked to Best Survival

When researchers analyzed the data years later, they discovered a striking pattern.

Women who slept between five and six-and-a-half hours per night had the highest survival rates after the follow-up period. On the contrary, the women who slept less than five hours or more than six-and-a-half hours were less likely to still be alive at the end of the study which was definitely not expected result of the study.

The results pretty much revealed what scientists describe as a “U-shaped relationship” between sleep duration and mortality risk. In other words, both very short and very long sleep durations had connections with higher mortality compared with moderate sleep.

Professor Daniel Kripke, a psychiatrist involved in the research, said the findings were surprising because they contradict the widespread belief that longer sleep is always healthier, and that consistently sleeping less than seven hours a night may result in bad health.

Why This Study Was Different

One key reason the study attracted attention is its methodology. Most previous sleep studies rely on the long standing tradition of questionnaires asking people how long they believe they sleep, which at times is believed to be less accurate especially when reported by aged adults not known for having good memory, but in this research study activity monitors were used to get more reliable results.

By using actigraphy, a wearable technology that records movement, researchers were able to measure sleep objectively. This approach is increasingly used in sleep science because it provides more reliable data on real-world sleep behavior.

Comparisons With Other Major Studies

The results differ somewhat from earlier large studies that found seven hours of sleep to be associated with the lowest mortality risk.

For example, analyses involving more than one million participants from the American Cancer Society’s Cancer Prevention Study showed that people sleeping around seven hours had the best survival rates, while both shorter and longer sleep durations were linked to higher mortality risk, which is not always the case as suggested by this study.

More recent population research has also suggested that very short sleep—around five hours—may increase risks of cardiovascular disease or early death. However, these studies often rely on self-reported sleep data rather than objective measurements, so the conclusions drawn from these researches are not always binding.

Why Sleep Matters for Health

Sleep plays a very critical role in maintaining the overall health of the body. During sleep, the body performs several vital functions, including repairing tissues, regulating hormones, and strengthening the immune system.

A lack of sleep has been associated with numerous health issues such as:

Elevated blood pressure Reduced glucose tolerance Increased risk of heart disease Impaired cognitive performance

Sleep deprivation is also one of the main reasons of unusual appetite and metabolic disorder, causing people to eat more and potentially gain weight.

Understanding Individual Sleep Needs

Despite the findings, scientists emphasize that sleep requirements differ from person to person. Factors such as age, genetics, lifestyle, and health conditions can all affect how much sleep someone needs to function well.

The study’s results do not necessarily mean everyone should aim for five hours of sleep. Instead, they highlight a very important point that the sleep quality and individual biology may be just as important as total sleep duration.

For some people, a shorter sleep schedule may still support good health and longevity.

Reassurance for Short Sleepers

Professor Kripke noted that many people worry about not achieving the recommended eight hours of sleep every night. However, the research suggests that moderate sleep—particularly around five to six hours—may not be harmful for some individuals.

“People who sleep five or six hours may be reassured,” he said, emphasizing that this duration appeared consistent with strong survival outcomes in the study group.

Nevertheless, researchers stress that more studies are needed to understand why different sleep durations influence health and longevity.