The best time when your body rests and heals is when you sleep. As you sleep you pass through various stages of sleep, each having a unique purpose. A good night’s sleep can give you a chance to spend enough time in the deep sleep stage as it offers a lot of benefits. How much sleep is right for you? How much deep sleep do you need by age?
Let us look at deep sleep and its requirement as per age in detail.
How Much Deep Sleep Do You Need By Age?
Your sleep requirements often vary as you age. How much deep sleep you need by age depends on many factors. But it is known that the need to sleep more is high during infancy and childhood. Later as you grow up your overall sleep decreases. By adulthood, most healthy people need about seven to eight and a half hours of sleep per day.1
Experts believe that how much sleep you need varies depending on genetic factors, age, and other factors, including an individual’s health. Hence, although sleep recommendations give a general guideline a person’s individual needs can be assessed with the advice of a doctor.2
How much deep sleep do you need by age? This is a commonly asked question.
Sleep duration recommendations2 include
- Newborns – 14 to 17 hours
- Infants – 12 – 15 hours
- Toddlers – 11 – 14 hours
- Preschoolers – 10- 13 hours
- Children – 9 – 11 hours
- Teenagers – 8 – 10 hours
- Young adults – 7 – 9 hours
- Adults – 7 – 9 hours
- Older adults (more than 65 years) – 7 – 8 hours
To understand how much deep sleep you need by age, it is necessary to know about the sleep stages. There are two phases of sleep – non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. A sleep episode begins with NREM sleep, passing through short periods of stages 1 and 2, then progressing into stages 3 and 4, which is the deep sleep stage, and finally into the REM sleep.3 This cycle continues during the entire night and the average length of the NREM-REM sleep cycle is about 70 to 100 minutes.3
Sleep stages 3 and 4 together form the slow wave deep sleep stage and most of it occurs during the first third of the night. Stage 3 last for a few minutes making about 3 to 8% of your sleep and stage 4 lasts for 20 to 40 minutes in the first cycle and accounts for 10 to 15% of sleep. Thus, you spend about 75% of your sleep in the NREM stage, which includes the deep sleep stage, which accounts for about 13 to 23%.3
Your body heals during the deep sleep stage, repairs tissues, restores energy, builds bones, strengthens the immune system, and promotes good health. The sleep architecture changes with age as how sleep is initiated, and maintained, the time spent in each sleep stage, and sleep efficiency varies from infancy to old age.
Deep Sleep Needs In Children
At birth, sleep time is distributed throughout the day without any specific rhythm. Circadian rhythms begin to take action from the age of 2 to 3 months when wakefulness during the day and longer periods of sleep at night begin to increase. After 3 months, the sleep cycles become more regular, and spends more time in deep sleep. By 6 months the longest sleep period increases to around 6 hours.
In ages 2 to 5 years the total sleep time decreases by 2 hours. Studies have shown that children spend more time during deep sleep stages than adolescents. Also, it is noted that the deep sleep needs gradually decrease with advancing pubertal development, and the time spent in stage 2 sleep increases.
Deep Sleep Needs In Adults
With advancing age, between 20 to 60 years, the rate of deep sleep or slow wave sleep stages decreases at the rate of about 2% per decade. This also results in episodes of frequent waking in older adults. However, experts believe that the ability to sleep becomes a challenge but the need to sleep does not decrease with age.3
Deep Sleep Need In Women
Some variations that may determine how much deep sleep you need by age also include gender differences. Women of 70 years and older spend about 15 to 20 % of total sleep time in deep sleep stages as compared to men of the same spending around 5%.3
Thus, it is clear that you may spend about two hours in deep sleep during adulthood.
Why Deep Sleep Is Important?
A 2000 study reported that the percentage of deep sleep, shown by slow wave decreased from 18.9% during early adulthood (16 – 25 years) to 3.4 % during middle age (36 – 50 years). The deep sleep was replaced by light sleep stages with no significant changes in sleep fragmentation or reduction in REM sleep. It also showed that there was no significant decrease in the slow wave deep sleep during the transition from middle age to older ages (71 – 83 years). But there was an increase in the wake time of 28 minutes per decade in both light sleep and REM sleep stages.
Further, the study also concluded the relationship between hormone secretion during the deep sleep stages and their impact on advancing age. As deep sleep declined from early adulthood to middle age, the secretion of growth hormones reduced to a great extent. However, there was not much difference from middle age to old age. Increasing age is also linked with rising cortisol levels, which was more significant after 50 years of age, when sleep became more fragmented and REM sleep reduced, although deep sleep was not much affected.4
The secretion of these hormones is linked with the increasing risk of metabolic disorders like weight gain, diabetes, chronic stress, and heart-related conditions with increasing age. When considering how much deep sleep you need with age, it is important to understand that good quality sleep can provide deep sleep and its benefits, which are more essential as you age.
It is commonly thought that older adults do not need to sleep for long as young adults. But in fact, older adults need adequate sleep or about seven to eight hours during the day. It is possible that as age advances, many older adults are not able to sleep for long during the night. Also, some may feel tired during the day. Many older adults may be light sleepers or tend to wake up early in the morning. This means that they may need a short nap in the afternoon to make up for the recommended hours of sleep 24 hours.
Sleep duration recommendations have ranges of optimal sleep and sleep durations that are too short or too long have been associated with negative effects on health. Long sleep hours may be due to the inability to fall asleep on time or not being able to sleep well throughout the night. However, studies have confirmed that regularly sleeping for long hours can be equally harmful to your health. Long sleep is associated with health problems like depression and chronic pain.2 Hence, sleeping for optimum hours is necessary.
You will be able to understand if you are not getting as much deep sleep as needed if you experience complaints like sleep disturbances at night, waking up unrefreshed, or feeling fatigued during the day. For sleep concerns, you can seek a medical opinion and plan a sleep test to determine the quality of your sleep, breathing rate, heart rate, oxygen levels, and brain waves during your sleep period.
Sleep health is largely based on sleep quality and sleep timing, in addition to the number of hours slept and sleep must receive attention as an important parameter for healthy living. How much deep sleep you need depends on your health but generally, younger people need more deep sleep as it promotes growth and development. However, aging people also need enough deep sleep to maintain good health but some may face difficulty in sleeping during the night when medical help can be sought.