Association between high nocturnal blood pressure andwhite matter change and its interaction by obstructive sleep apnoea among normotensive adults

Objectives: A reverse dipping pattern, characterized by higher night-time blood pressure (BP) than daytime BP, is associated with the increased risk for cerebrovascular disease, cardiovascular events and all-cause mortality. However, little has known about the association between white matter change (WMC) and reverse dipping pattern, particularly in normotensive adults. We aimed to examine whether WMC is associated with BP dipping patterns as measured with a 24-h ambulatory BP monitoring and whether obstructive sleep apnoea (OSA) is involved in this relationship Methods: A total of 703 normotensive adults were from an ongoing longitudinal study in a general population. WMC was measured with brain MRI. BP dipping patterns were defined as the ratio of the change in night-time and daytime SBP. OSA was categorized with the apnoeahypopnea index, as measured with polysomnography. To avoid the influence of hypertensive medications, we only included normotensive adults for the final analysis. To examine the associations between WMC and dipping patterns, we built logistic models. To elucidate the role of OSA, we also conducted both modification and mediation tests. Results: Reverse dipping pattern was significantly associated with WMC (odds ratio 1.49, 95% confidence interval 1.02-2.18). Further, OSA modified the association between dipping patterns and WMC (P=0.0118). No mediation effect of OSA was assessed. Conclusion: In 703 normotensive adults, the reverse dipping pattern showed a significant association with WMC, after adjusting for covariates. Further, according to the presence of OSA, the association between reverse dipping and WMC was varied.