Pattern & correlates of neurocognitive dysfunction in Asian Indian adults with severe obstructive sleep apnoea.

BACKGROUND & OBJECTIVES: No published data are available on neurocognitive dysfunction in Asian Indians with obstructive sleep apnoea (OSA). We therefore, studied the pattern and correlates of neurocognitive dysfunction in Indian adults with severe OSA. METHODS: Fifty patients aged 25-65 yr with severe OSA (apnoea-hypopnoea index>30) and 25 age, sex, and education level-matched normal controls were studied. Both groups were administered a standardized battery of neurocognitive tests. RESULTS: Patients with severe OSA had significantly impaired performance on tests of alertness, working memory, response inhibition, problem solving, and executive function. However, the difference in executive function between the groups disappeared after adjusting for delayed information processing. The test scores did not correlate with apnoea-hypopnoea index, arousal index, or Epworth sleepiness score. However, the percentage of time spent at <90 per cent oxygen saturation had a weak correlation with the number of stroop errors (Spearman's rho=0.64; P=0.033), number of trials required (rho=0.05; P=0.02), and perseverative errors on Wisconsin card sorting test (rho=0.36; P=0.02). INTERPRETATION & CONCLUSIONS: Our results suggested that delayed information processing rather than impaired abstract thinking was probably the cause of impaired performance on composite tests of neurocognitive function in patients with severe OSA.