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Sleep needs vary across ages and are especially impacted by lifestyle and health. Thus, to determine how much sleep you need, it's important to assess not only where you fall on the "sleep needs spectrum," but also to examine what lifestyle factors are affecting the quality and quantity of your sleep such as work schedules and stress. To get the sleep you need, you must look at the big picture.
Though research cannot pinpoint an exact amount of sleep need by people at different ages, the preceding table identifies the "rule-of-thumb" amounts most experts have agreed upon. Nevertheless, it's important to pay attention to your own individual needs by assessing how you feel on different amounts of sleep. Are you productive, healthy and happy on seven hours of sleep? Or does it take you nine hours of quality ZZZs to get you into high gear? Do you have health issues such as being overweight? Are you at risk for any disease? Are you experiencing sleep problems? Do you depend on caffeine to get you through the day? Do you feel sleepy when driving? These are questions that must be asked before you can find the number that works for you.
Not only do different age groups need different amounts of sleep, but sleep needs are also individual. Just like any other characteristics you are born with, the amount of sleep you need to function best may be different for you than for someone who is of the same age and gender. While you may be at your absolute best sleeping seven hours a night, someone else may clearly need nine hours to have a happy, productive life. In fact, a 2005 study confirmed the fact that sleep needs vary across populations, and the study calls for further research to identify traits within genes that may provide a "map" to explain how sleep needs differ among individuals.
Another reason there is "no magic number" for your sleep results from two different factors that researchers are learning about: a person’s basal sleep need – the amount of sleep our bodies need on a regular basis for optimal performance – and sleep debt , the accumulated sleep that is lost to poor sleep habits, sickness, awakenings due to environmental factors or other causes. Two studies suggest that healthy adults have a basal sleep need of seven to eight hours every night, but where things get complicated is the interaction between the basal need and sleep debt. For instance, you might meet your basal sleep need on any single night or a few nights in a row, but still have an unresolved sleep debt that may make you feel more sleepy and less alert at times, particularly in conjunction with circadian dips , those times in the 24-hour cycle when we are biologically programmed to be more sleepy and less alert, such as overnight hours and mid-afternoon.