An adult should regularly get 7-9 hours of sleep each night.
Regularly sleeping less than 7 hours is linked to various adverse health effects. Insufficient sleep is associated with weight gain and increased risk of obesity, carbohydrate metabolism disorders, lipid disorders, and elevated blood pressure.
Additionally, people sleeping less than 7 hours per day are more likely to suffer from heart disease, stroke, depression, and an increased risk of premature death. Less than 7 hours of sleep also leads to poorer immune system functioning and decreased overall physical and intellectual efficiency. Regularly sleeping more than 9 hours a day may be appropriate for young adults, those catching up on sleep deficits, and the sick. In other cases, sleeping more than 9 hours does not provide any health benefits and can even be harmful.
Although it’s often said that people need less sleep as they age, current sleep recommendations for all adult age groups are nearly identical. According to the National Sleep Foundation, individuals aged 18 to 64 should aim for seven or more hours of sleep each night, while those 65 and older should sleep seven to eight. Older individuals’ sleep patterns are shaped by many factors, from accompanying diseases to medications. For example, the body’s ability to metabolize alcohol decreases with age, which can disrupt sleep architecture and, thus, body regeneration.
The same applies to caffeine and nicotine. Both substances can make falling and staying asleep more difficult. Another factor affecting sleep problems is the lack of physical activity, which, combined with social isolation, can affect sleep quality. If you are less physically active during the day, it may be harder to maintain a regular sleep-wake rhythm. Moreover, social interactions provide essential signals for our body, helping maintain a normal sleep-wake rhythm.
Based on: https://doi.org/10.5665/sleep.4716