Clinical Manifestations

Area of Science:

• Chronobiology
• Neuroendocrinology
• Gerontology

Background:

• Nocturnal melatonin secretion is hypothesized to influence core body temperature (Tc) drop and cognitive function.
• Prior research has not investigated sex differences in the relationship between melatonin, Tc, and cognition.
• Understanding these sex differences is crucial for elucidating melatonin's potential pro-cognitive effects.

Purpose of the Study:

• To examine sex differences in the associations of melatonin (AUC and DLMO) with nocturnal core body temperature drop (Tdrop).
• To investigate sex differences in the associations of melatonin and Tdrop with cognitive function in older adults.

Main Methods:

• Sixty-five cognitively unimpaired older adults (32 females, 33 males) underwent a 60-hour laboratory study with sleep deprivation.
• Core body temperature (Tc) was continuously monitored, and salivary melatonin (AUC, DLMO) was measured hourly.
• Melatonin parameters were correlated with Tdrop (Tc_waking - Tc_sleep) and neurocognitive outcomes assessed later.

Main Results:

• Greater melatonin AUC correlated with greater Tdrop in both sexes, but with earlier timing in females.
• Earlier dim light melatonin onset (DLMO) correlated with greater Tdrop in both sexes.
• Melatonin AUC was linked to better memory and visuospatial function in females only; Tdrop was associated with executive function and attention in females, and language in males.

Conclusions:

• Melatonin release is strongly coupled to nocturnal Tdrop, with sex-specific differences in timing and strength.
• Elevated melatonin and Tdrop may offer cognitive protection, particularly for older females.
• Further research is needed to explore how aging-related changes, like menopause, influence these sex differences.