How much does melatonin actually improve sleep?
The short answer: melatonin helps, but the improvements are modest. In a meta-analysis of 10 randomized controlled trials in older adults with cognitive impairment, melatonin increased total sleep time by an average of 12.4 minutes [1]. That's a real, measurable gain—about the time it takes to brew a cup of coffee—but not a transformation of your sleep. Another trial in adults over 55 with insomnia found that a prolonged-release 2 mg dose shortened the time to fall asleep by about 9 minutes [5]. These effects are statistically significant, meaning they're unlikely to be due to chance, but they're small enough that many people might not notice a dramatic difference.
Higher doses may work better. A study that directly compared a low dose (0.3 mg) and a high dose (5 mg) in healthy older adults found that only the 5 mg dose significantly improved sleep efficiency—the percentage of time in bed actually spent asleep—during both nighttime and daytime sleep episodes [3]. The low dose showed only a trend toward improvement, and only during daytime sleep. So if you're considering melatonin, dose matters: 5 mg appears more effective than 0.3 mg for improving sleep quality.
Is melatonin safe for older adults, and does it have downsides?
Melatonin appears safe in the short term, with no major side effects reported in these studies. The 5 mg dose trial noted no adverse effects on next-day cognition or falls [3], and the prolonged-release 2 mg study found that daytime psychomotor performance (like reaction time and coordination) was actually better with melatonin than placebo [5]. That's important because many prescription sleep aids can cause morning grogginess or increase fall risk in older adults—melatonin seems to avoid those problems.
However, the evidence is limited to short-term use (weeks to a month). None of these studies tracked long-term safety for months or years. Also, melatonin is not a cure-all: the meta-analysis found no significant improvement in sleep efficiency, depression, or daily functioning [1], and a separate study showed that even with melatonin, sleep quality after surgery was still much worse than before surgery [2]. So while melatonin is a reasonable option, it's not a substitute for good sleep hygiene or treating underlying sleep disorders.
Who benefits most from melatonin, and what else can improve sleep?
Melatonin seems most helpful for older adults whose sleep problems are linked to low natural melatonin levels—for example, after surgery or in people with dementia. The surgery study found that patients who had surgery in the afternoon had higher melatonin levels and better sleep than those who had morning surgery, suggesting that timing matters because melatonin production follows a daily rhythm [2]. For older adults with cognitive impairment, melatonin also produced a small improvement in thinking skills (about 1.8 points on a 30-point mental status test) [1], which is a bonus.
But melatonin isn't the only lever. A large population study in Brazil found that people who did leisure walking were 34% more likely to get adequate sleep, and those who met physical activity guidelines were 16% more likely to report good sleep quality [4]. That's a bigger effect than melatonin's 12-minute sleep increase. So combining melatonin with regular physical activity—even just a daily walk—may give you the best chance of better sleep.
About These Sources
This answer is built on 5 peer-reviewed studies — published from 2009 to 2025, 1 from 2024 or later, 1 in Q1 journals, collectively cited 63 times — selected as the most relevant from 5 studies that passed quality screening, drawn from 53 papers retrieved from a database of over 500 million.
Sources used in this answer
Melatonin for sleep and cognitive outcomes in older adults with cognitive impairment: a meta-analysis of randomised controlled trials.
A meta-analysis of 10 RCTs (n=516) in older adults with cognitive impairment found melatonin increased total sleep time by 12.4 minutes and improved cognition by 1.8 points on the MMSE, but effects on sleep efficiency and depression were not significant.
The Impact of Morning Surgery or Afternoon Surgery on Postoperative Sleep Quality and Melatonin Levels of Elderly Patients: A Prospective, Randomized Study
A randomized trial of 60 elderly hip surgery patients found that afternoon surgery led to better sleep quality and higher melatonin levels than morning surgery, but both groups had much worse sleep than before surgery.
High dose melatonin increases sleep duration during nighttime and daytime sleep episodes in older adults
In a crossover study of 24 healthy older adults, 5 mg melatonin significantly improved sleep efficiency during both day and night, while 0.3 mg only showed a trend toward improvement during daytime sleep.
Physical Activity and Sleep in Adults and Older Adults in Southern Brazil
A cross-sectional study of 820 adults in Brazil found that leisure walking was associated with 34% higher likelihood of adequate sleep duration, and meeting physical activity guidelines with 16% higher likelihood of good sleep quality.
The effect of prolonged-release melatonin on sleep measures and psychomotor performance in elderly patients with insomnia.
A randomized trial of 40 older adults with insomnia found that prolonged-release 2 mg melatonin shortened sleep onset by 9 minutes and improved perceived sleep quality, with no impairment of daytime psychomotor performance.