Use of Melatonin to Promote Sleep in Older People

Abstract

Many older Americans purchase the hormone melatonin and take it orally, nightly, to promote sleep onset and to help them fall back asleep after the frequent nocturnal awakenings associated with aging. This need for exogenous melatonin reflects the fact that the progressive calcification of the human pineal diminishes the organ’s ability to secrete its hormone, so that instead of plasma melatonin levels rising normally by 10-fold or more around bedtime the rise may be only by twofold, or even less. The quantity of melatonin that most aging people need to restore nocturnal plasma melatonin levels to what they are in youth—and, concurrently, to promote sleep—is tiny, only about 0.2–0.5 mg. However, this dosage is generally unavailable, so patients may take doses 10-fold greater, or more, producing side-effects (e.g., hypothermia; hypoprolactinemia; morning grogginess) and ultimately desensitizing melatonin receptors in the brain. The reasons that low-dose melatonin is generally unavailable are described and a strategy is proposed for enabling patients to consume the correct dosage even when preparations containing that dosage cannot be obtained.