During sleep, the body regulates essential functions, consolidates memory, and carries out repair and recovery processes. Sufficient, high-quality rest is linked to better cardiovascular and metabolic health, a more balanced immune system, and a lower risk of developing certain long-term health problems. In short, sleep is key to active longevity.
When we think of a "good night's sleep," we mostly associate it with the number of hours we have slept. However, the body also pays attention to our schedules: when we go to bed, when we wake up, and how much these times change from one day to the next.
Science is beginning to suggest that sleeping consistently could be just as important as getting the right number of hours. It is not about going to bed every night with a clock in your hand, but rather providing the body with sufficiently constant signals so it can organize rest, hormonal activity, and the repair processes that take place while we sleep.
How many hours do you need to sleep to live longer?
In general terms, adults need between seven and nine hours of sleep each night. This need does not disappear with age. According to the National Institute on Aging, although older adults tend to have lighter sleep and wake up more often, they still need around seven to nine hours.
When analyzing the relationship between sleep duration and mortality, studies find a “U”-shaped curve. The risk is lowest in the central zone, around seven or eight hours, and increases at both extremes: when we sleep too little and when we habitually sleep much more. A 2025 meta-analysis on sleep duration and mortality gathered 79 follow-up studies. Compared to sleeping between seven and eight hours, sleeping less than seven was associated with a 14% higher risk of all-cause mortality. Sleeping nine hours or more was linked to a 34% increase.
What are the risks of sleeping less than 7 hours?
Sleeping less than seven hours on an occasional basis does not have the same meaning as doing so almost every night. Problems begin when insufficient sleep becomes the norm and the body loses part of the time it needs to recover, day after day. In the short term, lack of sleep can affect attention, memory, mood, and reaction time. It can also increase appetite and make emotional regulation difficult. In the long term, habitually sleeping too little is linked to an increased risk of hypertension, cardiovascular disease, and diabetes.
Furthermore, tiredness does not always accurately reflect a lack of sleep. It is possible to get used to functioning on six hours and stop feeling particularly sleepy, even though attention, metabolism, and physical recovery continue to be affected.
Sleep regularity as a determining factor
Sleep regularity describes the extent to which we maintain a similar sleep-wake pattern from one day to the next. It includes the time we fall asleep, the time we wake up, naps, and nightly interruptions.
A person can sleep eight hours every night and still have an irregular pattern. For example, they might sleep from 11:00 p.m. to 7:00 a.m. on weekdays and from 2:00 a.m. to 10:00 a.m. on the weekend. The duration is the same, but the schedule has shifted by three hours. This difference matters because sleep is not an isolated block within the day. It is part of a system of biological rhythms that also organizes body temperature, appetite, hormone release, blood pressure, and alertness levels.
Differences between sleep duration, quality, and regularity
Although they are related, duration, quality, and regularity describe different aspects:
- Sleep duration is the total time we spend sleeping.
- Sleep quality indicates whether the rest has been continuous and restorative. It takes into account aspects such as difficulty falling asleep, nighttime awakenings, or feeling tired upon waking.
- Sleep regularity reflects how similar our schedules and rest patterns are from one day to the next.
Is it more important to sleep regularly than to sleep eight hours?
Duration remains fundamental, but some research indicates that regularity may predict certain health risks better than the average number of hours slept.
Sleep regularity and mortality risk
In the study on sleep regularity published in the journal Sleep, participants with more regular patterns showed between 20% and 48% less relative risk of all-cause mortality than the group with the most irregular sleep. Favorable associations were also observed with mortality from cancer and cardiometabolic causes, which include cardiovascular and metabolic diseases.
Another study with 88,975 participants from the UK Biobank reached a similar conclusion. People in the most irregular schedules showed a 53% higher relative risk of mortality than those in the middle range of regularity. At the opposite extreme, very regular patterns were associated with an additional reduction of nearly 10%.
These percentages must be interpreted correctly. These are observational studies: they find a relationship, but they do not prove that changing one's sleep schedule will automatically reduce a person's risk by that same proportion. Those who sleep with greater regularity may also have more stable jobs, exercise more, maintain more consistent meal times, or be in better health. Even so, the researchers adjusted the results to account for numerous health and lifestyle factors, and the association remained. The consistency across independent studies reinforces the idea that regularity is a dimension of sleep health in its own right and not a minor detail.
How do irregular sleep schedules affect health?
The body does not wait for us to look at the clock to know what time it is. It uses cues such as light, darkness, meals, exercise, and our routines to anticipate when it should be active and when it should prepare to rest.
When these signals arrive at a different time each day, internal rhythms can lose coordination. It does not mean that a late dinner or a night out celebrating will harm our health. The problem is sustained irregularity: frequent changes that force the body to readjust over and over again.
Circadian rhythm: the internal clock that regulates sleep
The circadian rhythm is the approximately 24-hour biological cycle that organizes numerous body functions. It is coordinated by an area of the brain that receives information about ambient light and uses that signal to synchronize sleep and wakefulness.
Going to bed and waking up at very different times alters the relationship between these signals and our behaviors. It is somewhat like experiencing small time zone changes without having traveled. This is why the term “social jet lag” is used to describe the difference between the schedule on workdays and the one on days off. Maintaining some stability, especially in the wake-up time, helps the internal clock receive a clearer daily reference. Natural light in the morning, eating at similar times, and regular exercise also contribute to reinforcing that signal.
What is the relationship between melatonin and the circadian rhythm?
Melatonin is a hormone that the body produces mainly when light decreases. Its function is not to "turn off" the brain suddenly, but to signal that the nighttime phase has arrived and it should prepare to sleep.
Normally, its levels begin to rise in the evening, remain elevated during part of the early morning, and fall as morning approaches. Exposure to intense light at night, especially when combined with changing schedules, can delay this signal.
Melatonin works together with another mechanism: sleep pressure. This pressure accumulates as the hours of wakefulness pass and explains why we feel a greater need to sleep at the end of the day. To fall asleep well, it is best for both signals to coincide: that we have been awake long enough and that the circadian clock recognizes that night has arrived.
For this reason, a regular routine facilitates the process. If we change our bedtime significantly every night, fatigue and the circadian signal may stop occurring at the same time.
Deep sleep, cellular repair, and growth hormone
Throughout the night, we go through several sleep cycles. One of their components is non-REM deep sleep, a phase in which brain activity slows down and the body carries out part of its physical recovery processes. Deep sleep is closely linked to the release of growth hormone. Although its name is usually associated with childhood, this hormone is also important in adulthood because it participates in the maintenance of muscles and bones, tissue repair, and the regulation of metabolism.
Research published in the journal Cell identified the brain circuit in mice that connects sleep phases with the release of this hormone. The researchers observed a feedback system: sleep influenced the secretion of growth hormone, and this, in turn, participated in the regulation of sleep and wakefulness. As this was an animal study, its results cannot be directly applied to people. However, it helps biologically explain something that has long been observed: sleeping is not remaining inactive, but entering an organized state in which the brain and body perform essential maintenance functions.
What sleep habits help with active longevity?
There is no single habit capable of guaranteeing healthy aging. What seems to make the difference is the sum of various behaviors maintained over time. A healthy pattern for sleep could be built as follows:
- Wake up at a similar time every day, including weekends.
- Get exposed to natural light during the morning.
- Exercise regularly.
- Create a quiet routine before going to bed.
- Reduce caffeine during the second half of the day.
- Avoid using alcohol as a sleep aid, as it can fragment rest.
- Keep the bedroom dark, quiet, and at a comfortable temperature.
- Consult a professional if you experience intense snoring, breathing pauses, persistent insomnia, or daytime sleepiness that is difficult to control.
What is melatonin for and when can it help with sleep?
The melatonin produced by the body acts as a time signal: it informs the body that night is coming. It can also be taken as a supplement when there is difficulty falling asleep or when the internal clock needs to adapt to a time change.
The European Food Safety Authority recognizes that melatonin contributes to reducing the time needed to fall asleep. This claim can be used on products that provide 1 milligram of melatonin per serving, and the beneficial effect is obtained by taking that amount shortly before bedtime.
At Mr. Loris, we have just added a new melatonin to accompany the nightly routine when it is hard to fall asleep. You can check its composition, usage instructions, and warnings here before deciding if it fits your needs. Because the basis remains the same: it is not just about sleeping more, but about helping the body recognize when the time for sleep has arrived. Melatonin can support that routine, but regularity is what gives it structure.
