Alzheimer's Disease and Melatonin
Melatonin is a natural hormone that regulates sleep. At night, the pineal gland stops producing serotonin and instead makes melatonin. This melatonin release helps trigger sleep. Studies have shown that melatonin, along with light therapy (exposure to bright light during daylight hours) may help Alzheimer's patients with quality of sleep and mood.
Effect of Melatonin on Alzheimer's Disease
The combination of melatonin and light therapy (bright light exposure during daylight hours) has shown to improve both mood and quality of sleep, which can be significant part of Alzheimer's symptoms.
Research Evidence on Melatonin
In a sizable Danish trial, researchers investigated the effects of melatonin and light therapy (bright light exposure during daylight hours) on mood, sleep, and cognitive decline in elderly patients, most of whom suffered from dementia.85 They found that melatonin 2.5 mg, given nightly for an average of 15 months, slightly improved quality of sleep, but it worsened mood. Melatonin apparently had no significant effect on cognition. On the other hand, light therapy alone slightly decreased cognitive and functional decline and improved mood. Combining melatonin with light therapy improved mood and quality of sleep.
Side Effects and Warnings
A safety study found that melatonin at a dose of 10 mg daily produced no toxic effects when given to 40 healthy males for a period of 28 days. ^ However, this does not prove that melatonin is safe when taken on a regular basis over the long term. Keep in mind that melatonin is not truly a food supplement but a hormone. As we know from other hormones used in medicine, such as estrogen and cortisone, harmful effects can take years to appear. Hormones are powerful substances that have many subtle effects in the body, and we're far from understanding them fully. While in one small study, use of melatonin over an 8-day period by healthy men did not affect natural release of melatonin or levels of pituitary or sex hormones, ^ another study found effects on testosterone and estrogen metabolism in men and possible impairment of sperm function. ^ Also, a small study in women found possible effects on the important female hormone called LH (luteinizing hormone). ^ Melatonin appears to cause drowsiness and decreased mental attention for about 2 to 6 hours after using it and may also impair balance. ^ For this reason, you should not drive or operate machinery for several hours after taking melatonin. In a study of healthy middle-aged and older adults, however, an extended release version of melatonin, which is said to more closely mimic natural fluctuations of the hormone in the body, did not impair mental ability or driving skills 1 to 4 hours later compared to placebo. ^ In either case, melatonin does not appear to have any "hangover" effects the following day. ^ Based on theoretical ideas of how melatonin works, some authorities specifically recommend against using it in people with depression, schizophrenia, autoimmune diseases, and other serious illnesses. One study in postmenopausal women found evidence that melatonin might impair insulin action and glucose tolerance, suggesting that people with diabetes should not use it. ^ However, another study found melatonin safe and effective for people with diabetes. ^ Because of these contradictions, we suggest that individuals with diabetes seek physician supervision before using melatonin.
Two exceedingly preliminary studies reported by one research group has led to publicized concerns that use of the supplement melatonin might increase night-time asthma. ^ However, one double-blind study of melatonin in people with asthma found evidence of improved sleep without worsening of symptoms. ^ Again, at the current state of knowledge, caution must be advised for people with night-time asthma who wish to try melatonin.
There is some evidence that melatonin may interfere with the ability of blood to clot normally, at least in healthy volunteers, ^ though the clinical significance of this finding is at yet unknown.
Maximum safe dosages for young children, pregnant or nursing women, or those with serious liver or kidney disease have not been established.