Why do we work and play during the day and sleep at night? It seems like an easy question to answer. But the truth is that it has little to do with social patterns or habits. In fact, scientists are just beginning to understand sleep cycles and how they are affected by daylight and darkness.
Of particular concern to scientists is the role of naturally produced hormones in the body and how they can either wake us up or put us to sleep. One hormone that has been studied extensively is called melatonin .
Melatonin is produced by the pineal gland and it is not released until the sun goes down. Once it enters the blood, melatonin works as a natural soporific that lowers the heart rate and makes people feel more relaxed. This process often begins about an hour after sundown.
The effectiveness of melatonin goes a long way to explaining why people feel tired much earlier during the winter months, when the days are shorter. It also explains why people generally sleep better during the winter than they do in the summer months.
The pineal gland continues to produce melatonin all night long. It is believed that higher levels of the hormone in the blood actually encourage longer and deeper sleep. By daybreak, melatonin levels return to normal.
Studies have shown that melatonin production naturally decreases with age, which may have an effect on normal sleep patterns. For this reason, melatonin is a popular supplement/sleep aid for elderly people.