Generally speaking, 40 years old is belong to adult, sleep need 7-9 hours, if <6 hours, belong to sleep decrease, >11 hours belong to sleep increase, this is only for most people. There are a small number of people who are particularly energetic and may have 5-6 hours enough; there are also some people who may need a long time, but the quality of sleep is not necessarily very high, mainly depending on whether the work and life on the 2nd day is affected. If the work and life on the second day are not affected and you have a lot of energy, it does not matter much if the time is a little less or a little more. All in all, 7-9 hours of sleep is suitable for most adults around 40 years old.