The effect of magnesium supplementation on primary insomnia in elderly: a double-blind placebo-controlled clinical trial
8-week RCT in elderly with insomnia: 500mg/day magnesium significantly improved subjective insomnia score, sleep efficiency, sleep onset latency, and serum melatonin concentration.
BACKGROUND: Nearly 50% of older adults have insomnia, with difficulty in getting to sleep, early awakening, or feeling unrefreshed on waking. With aging, several changes occur that can place one at risk for insomnia, including age-related changes in various circadian rhythms, environmental and lifestyle changes, and decreased nutrients intake, absorption, retention, and utilization. The natural N-methyl-D-aspartic acid (NMDA) antagonist and GABA agonist, Mg(2+), seems to play a key role in the regulation of sleep. The objective of this study was to determine the efficacy of magnesium supplementation to improve insomnia in elderly. MATERIALS AND METHODS: A double-blind randomized clinical trial was conducted in 46 elderly subjects, randomly allocated into the magnesium or the placebo group and received 500 mg magnesium or placebo daily for 8 weeks. Questionnaires of insomnia severity index (ISI), physical activity, and sleep log were completed at baseline and after the intervention period. Anthropometric confounding factors, daily intake of magnesium, calcium, potassium, caffeine, calories form carbohydrates, and total calorie intake, were obtained using 24-h recall for 3 days. Blood samples were taken at baseline and after the intervention period for analysis of serum magnesium, renin, melatonin, and cortisol. Statistical analyses were performed using SPSS19 and P values < 0.05 were considered as statistically significant. RESULTS: No significant differences were observed in assessed variables between the two groups at the baseline. As compared to the placebo group, in the experimental group, dietary magnesium supplementation brought about statistically significant increases in sleep time (P = 0.002), sleep efficiency (P = 0.03), concentration of serum renin (P < 0.001), and melatonin (P = 0.007), and also resulted in significant decrease of ISI score (P = 0.006), sleep onset latency (P = 0.02) and serum cortisol concentration (P = 0.008). Supplementation also resulted in marginally between-group significant reduction in early morning awakening (P = 0.08) and serum magnesium concentration (P = 0.06). Although total sleep time (P = 0.37) did not show any significant between-group differences. CONCLUSION: Supplementation of magnesium appears to improve subjective measures of insomnia such as ISI score, sleep efficiency, sleep time and sleep onset latency, early morning awakening, and likewise, insomnia objective measures such as concentration of serum renin, melatonin, and serum cortisol, in elderly people.
Abstract sourced from PubMed, a database of the U.S. National Library of Medicine. Displayed in the authors’ own words for context; our critique is in the sections below.
How to read a study like this
The same questions worth asking about any research paper, not just this one. Worth a minute even if you trust the grade.
Supplement effects often depend on baseline status. Vitamin D helps people who are deficient; iron helps people who are anemic. A result in people unlike you may not apply to you.
A study that shows a blood marker moved isn't the same as a study that shows people felt or functioned better. Ask what the outcome means in practice.
'Statistically significant' only means the effect is unlikely to be zero. It doesn't tell you the effect is large enough to notice. Look for effect sizes, not just p-values.
Industry-funded trials are several times more likely to report positive results than independent ones. It's not usually fraud — it's subtle design and reporting choices. Weight accordingly.
Single positive trials are hypotheses. Replication by independent groups is what turns a hypothesis into reliable evidence. If the only positive trial is the one you're reading, wait.
Supplement marketing routinely cites trials that used 5–10× the dose in the product. If the effective dose was 2 g/day and the capsule has 200 mg, expect roughly no effect.
Not medical advice. This breakdown is for educational purposes. Nothing here constitutes an allegation of fraud or misconduct by any researcher or sponsor. Reasonable scientists can grade the same paper differently; we show our rubric and link every claim to the original study.