As we age, our bodies secrete lesser amounts of substances which help our bodies to decide when to sleep and when to wake up.
Levels of growth hormone which promotes deep sleep, and melatonin which regulates our sleeping and waking cycle decrease as we age. As a result, our circadian rhythm — the internal clock that tells us to go to sleep at night and wake up in the morning — changes. We find ourselves going to bed earlier and waking up earlier (sigh...).
Sometimes, we have our days and nights mixed up. Sleep cycle gets disrupted. We feel sleepy during days and can't sleep at nights (sigh...).
Therefore, people are taking melatonin in re-setting their normal sleep cycles. It supplements our melatonin levels and help to reset our biological clocks. So that, we can sleep better at night.
