This variation is apparently linked to individual biological rhythms and possibly heredity, and can vary greatly from one individual to another. Therefore, insomniacs might do well to experiment with different times of going to sleep and arising, to see if they can get a better synchronization with their natural body rhythms. Another factor that can affect sleep is age. People require less sleep as they grow older, and this becomes increasingly evident after age 55. There is sexism in tossing and turning.
Several studies indicate that women have more trouble with insomnia than men.
The question arises whether this is because, as with other physical or psychological complaints, women tend to seek help more often than men or whether there is an actual biological difference. It is known that women can be more easily roused from sleep than men and that, at an earlier age, they start requiring less sleep than men. In addition, there may be a hormonal factor, the sleepiness of early pregnancy due to progesterone release and the insomnia of premenstrual tension being two examples. Besides these factors, there are environmental variables, such as diet and exercise, which are more amenable to change. Interestingly, that old folk remedy for sleeplessness, a glass of warm milk, had some scientific basis.