Obstructive sleep apnoea and Alzheimer's disease pathology: a review of plausible pathological mechanisms and potential modifying impact of hypertension.

Alzheimer's Disease (AD) is estimated to account for up to 75% of all dementia cases, of which there is a global prevalence of 50 million. There are no curative treatments available for AD dementia, therefore, early identification of risk factors is paramount. Up to 40% of all dementia cases may be attributable to modifiable risk factors. One such risk factor is poor sleep. Obstructive sleep apnoea (OSA) is a common sleep disorder characterised by repeated upper airway collapse, contributing to intermittent hypoxaemia and sleep fragmentation. Hypertension is frequently comorbid with OSA and is an established risk factor for dementia, with recent literature exploring potential mechanistic contributions to AD pathogenesis. Despite current literature exploring associations between OSA and hypertension on AD individually, little research has investigated the potential combined impact of these two pervasive disorders. To this end, this review will synthesise existing literature investigating potential pathogenic mechanisms between OSA and AD, including oxidative stress and altered sleep architecture. Further, shared pathophysiological consequences of OSA and hypertension will be reviewed in the context of AD to highlight the potential for effective management in mid-life to preserve neurological and cognitive health in late life.