Cerebral oxygenation response to postural change using continuous near-infrared spectroscopy (NIRS) and its association with falls in older adults

BACKGROUND: Impaired cerebral perfusion during postural changes may contribute to fall risk in older adults. This study used near-infrared spectroscopy (NIRS) as a proxy for cerebral blood flow to investigate the association between cerebral oxygenation responses during postural changes and falls in older adults. METHODS: We analyzed parameters of oxygenated hemoglobin (OxyHb), deoxygenated hemoglobin (DeoxyHb), total hemoglobin (tHb), and tissue saturation index (TSI) during supine-to-stand and sit-to-stand maneuvers in the PROHEALTH cohort of older adults (n = 30; 23% with positive falls history; mean age 74 ± 7 years). Associations with falls were assessed using logistic regression. RESULTS: Significant associations with falls history were observed during the supine-to-stand maneuver, despite no significant differences in orthostatic cardiovascular responses. After adjusting for age and sex, lower OxyHb nadir-to-overshoot (OR = 5.20, 95% CI 1.06-25.57), lower TSI overshoot (OR = 1.86, 95% CI 1.04-3.33), and lower TSI initial recovery amplitude (OR = 1.86, 95% CI 1.04-3.34), all within the first minute of standing, were significantly associated with falls history. In addition, lower TSI steady-state values at 60-120 s after standing (OR = 1.56, 95% CI 1.01-2.42) also showed a significant association. No significant associations were observed for any of the parameters during the sit-to-stand maneuver. CONCLUSIONS: Impaired OxyHb and TSI responses, particularly within the first minute after standing and reduced TSI during sustained impaired recovery (60-120 s), were associated with falls in older adults. Supine-to-stand testing outperformed sit-to-stand testing in identifying cerebral oxygenation impairments. These findings highlight the clinical potential of NIRS as a practical tool for identifying orthostatic cerebral hypoperfusion-related fall risk. Further validation in larger, prospective cohorts is needed.