Interaction of obstructive sleep apnoea and cognitive impairment with slow gait speed in middle-aged and older adults.

Objective to investigate whether slow gait speed is associated with cognitive impairment and further whether the association is modified by obstructive sleep apnoea (OSA). Methods in total, 2,222 adults aged 49-80 years, free from dementia, stroke and head injury were asked to walk a 4-m course at fast and usual gait speeds. The time taken to walk was measured. All participants completed the Korean Mini-Mental State Examination, which was validated in the Korean language, to assess cognitive function. Additionally, the participants completed a polysomnography test to ascertain OSA (defined as an apnoea-hypopnoea index ≥15). Multivariable linear regression models were utilised to test the associations. Results time taken to walk 4 m showed significant inverse associations with cognitive scores (P value = 0.001 at fast gait speed and P = 0.002 at usual gait speed). Furthermore, a significant interaction according to OSA on the association between time to walk and cognitive impairment was found (P value for interaction = 0.003 at fast gait speed and P value for interaction = 0.007 at usual gait speed). Conclusion we found that the inverse association between the time taken to walk 4 m and a cognitive score became significantly stronger, if an individual had OSA.