Effects of saffron supplementation on improving sleep quality: a meta-analysis of randomized controlled trials

To compare the efficacy of different dosage regimens of saffron supplementation on improving sleep quality among healthy adults, patients with insomnia or type 2 diabetes and patients under Methadone maintenance treatment (MMT).

PubMed, Embase, The Cochrane Library and other databases were searched from inception until October 2021. Randomized controlled trials (RCTs) investigating the efficacy saffron supplementation on sleep quality were included. Data were extracted independently by 2 investigators and assessed the study quality by the Cochrane risk-of-bias tool. The measurements include Pittsburgh Sleep Quality Index (PSQI), Insomnia Severity Index (ISI) and Restorative Sleep Questionnaire (RSQ).

The pooling of the effect sizes showed that saffron group achieve a notable treatment effect on PSQI (MD: -2.14; 95% CI: -2.86 to -1.42; P < 0.01), ISI (MD: -2.63; 95% CI: -3.70 to -2.55; P < 0.01) and RSQ (MD: 7.05; 95% CI: 1.48 to 12.62; P = 0.01) compared with placebo group.

Saffron supplementation as a treatment for improving sleep quality have promising clinical application as its great improvement on all efficacy outcomes and no serious adverse advents occurred as the dose was increased. The dose of 100 mg saffron supplementation per day was proved to achieve excellent and more stable curative effect on improving sleep quality in our subgroup analysis. However, further investigation is necessary to confirm the efficacy and long-term safety of different doses of saffron for insomnia.