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.