Low-Dose Melatonin Improves Climacteric Symptoms and Sleep in Female Shift Workers: Randomized Controlled Trial
TL;DR
Low-dose melatonin (3mg/day, 1 hour before bed, 12 weeks) reduced climacteric symptom scores by 38%, improved sleep efficiency from 78% to 87%, and decreased anxiety scores by 32% in female shift workers.
Research Background
Female shift workers face a dual challenge: circadian rhythm disruption from shift work, and hormonal fluctuations from the climacteric period that affect sleep. Yet intervention research targeting this specific population is extremely limited.
Published in the Journal of Pineal Research in 2026, this RCT by a University of São Paulo team evaluated the effects of low-dose melatonin on climacteric symptoms, sleep, and mood in female shift workers. The study enrolled 64 women aged 40-60 who worked shifts (including nights) and had climacteric symptoms, randomized to melatonin (3mg/day, 1 hour before bed) or placebo for 12 weeks.
Key Findings
1. Significant Climacteric Symptom Improvement
Kupperman Index (KI):
| Measure | Melatonin | Placebo |
|---|---|---|
| KI total change | -38% | -12% |
| Hot flashes/night sweats | -41% | -15% |
| Insomnia symptoms | -45% | -18% |
| Mood swings | -36% | -10% |
2. Sleep Quality Improvement
| Measure | Melatonin | Placebo |
|---|---|---|
| Sleep efficiency | 78.1% → 87.3% | 78.5% → 80.1% |
| Sleep onset latency | -17 min | -4 min |
| PSQI score | -3.6 pts | -1.1 pts |
3. Mood Improvement
- Anxiety (HADS-A): -32% (placebo: -8%)
- Depression (HADS-D): -28% (placebo: -9%)
- Quality of life (MENQOL): 2.4× improvement vs placebo
4. Good Safety Profile
No significant difference in adverse events. Mild morning drowsiness (3 cases) and headache (2 cases) in the melatonin group, all resolved within 1-2 weeks.
What This Means
Melatonin's "added value": Beyond sleep, melatonin significantly improves climacteric symptoms and mood in female shift workers — likely due to its combined effects as a circadian regulator and antioxidant.
Dose strategy matters: 3mg low dose is effective; no need for higher doses. Timing 1 hour before planned sleep is critical for circadian re-synchronization.
Filling a clinical gap: Shift work in climacteric women has been neglected — this is the first melatonin RCT targeting this population.
Practical Recommendations
- Dose: 3mg/day (low dose, avoid next-day drowsiness from high doses)
- Timing: 1 hour before planned sleep time
- Duration: At least 4-8 weeks to assess effectiveness
- Note: Shift workers with irregular schedules should fix "bedtime" as consistently as possible
Study Limitations
- Moderate sample size (n=64)
- Only 12-week evaluation; longer-term safety needs study
- No subgroup analysis by shift type (fixed night vs rotating)
- Primarily questionnaire-based outcomes; no objective sleep monitoring
References
Frequently Asked Questions
Short-term (up to 12 weeks) is well-tolerated. For long-term use, periodic breaks (e.g., 1 week off every 3 months) are recommended. Consult your doctor for extended use.