Age differences in overnight breath hydrogen dynamics and their association with sleep physiology

Oxidative stress increases with aging and may influence both sleep physiology and gut microbial activity. Molecular hydrogen, produced by intestinal fermentation, acts as an endogenous antioxidant and can be measured noninvasively in exhaled breath. However, age- and sex-related differences in nocturnal changes of breath hydrogen remain unclear. We analyzed breath hydrogen and methane levels in 166 healthy adults aged 20-85 years. Participants self-collected end-alveolar breath samples at home before sleep and immediately after waking. Breath hydrogen and methane levels were determined by gas chromatography. The older group (n= 91) showed significantly lower breath hydrogen levels after waking compared with the non-older group (n= 75), despite no differences before sleep. No significant sex-related differences were observed. The older group also reported more frequent nocturnal awakenings. These findings suggest that age-related changes in hydrogen dynamics may be associated with sleep-related physiological processes. The overnight change in breath hydrogen was significantly greater in the older group compared with the non-older group, indicating a larger overnight reduction in hydrogen levels in older adults. No significant differences in breath methane levels were observed between groups. Age-related alterations in gut microbiota, gastrointestinal motility, and redox balance may contribute to reduced morning hydrogen levels. Breath hydrogen measurement represents a simple, noninvasive biomarker for assessing physiological changes associated with aging and sleep.