TOPLINE:

Low nocturnal melatonin secretion, measured using the urinary 6-sulfatoxymelatonin-to-creatinine ratio (aMT6s/Cr), was independently associated with an increased risk for incident type 2 diabetes (T2D), suggesting its potential as a biomarker for the risk assessment of T2D.

METHODOLOGY:

• Researchers in Sweden conducted a prospective cohort study to investigate the association between nocturnal melatonin secretion and the risk for incident T2D in adults.
• They included 4491 adults (mean age, 42.6 years; 52% women) from the Malmö Offspring Study who neither had T2D nor were receiving melatonin supplements.
• Nocturnal melatonin secretion was measured using the aMT6s/Cr from the first morning urine samples and categorised into sex-specific quintiles.
• Cases of incident T2D were tracked using data from national and regional health registers.

TAKEAWAY:

• During the median follow-up of 6.5 years, 171 participants developed T2D, with a corresponding incidence rate of 5.93 per 1000 person-years.
• Participants in the lowest quintile of aMT6s/Cr showed a 54% higher risk for incident T2D than those in higher quintiles (hazard ratio [HR], 1.54; P = .01), after adjusting for several confounders.
• Those with higher nighttime melatonin levels had about a 17% lower risk of developing T2D (HR, 0.83; P = .01).

IN PRACTICE:

"Our findings suggest that low nocturnal melatonin secretion may serve as an early biomarker of T2D risk, complementing established metabolic and lifestyle predictors," the authors wrote.

SOURCE:

This study was led by Einar Sojakka Smith, MD, PhD, Department of Clinical Sciences in Malmö, Lund University, Malmö, Sweden. It was published online on December 13, 2025, in The Journal of Clinical Endocrinology & Metabolism.

LIMITATIONS:

This study relied on single morning urine samples to estimate melatonin secretion, which may not have captured day-to-day variability. The possibility of residual confounding cannot be excluded. This study lacked data on genetic information related to metabolism or T2D susceptibility.

DISCLOSURES:

Two authors reported receiving grants from the Swedish Research Council and other sources. The authors declared having no relevant conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.