Association between nocturnal variation in blood pressure and risk of acute ischemic stroke: a systematic review

Objective: Blood pressure (BP) is a dynamic parameter characterized by fluctuations during the 24-hour period. Variability of BP has been associated with cardiovascular risk and the occurrence of acute ischemic stroke (AIS). Circadian variation in BP during the night shows some basic patterns. The purpose of this study is to to correlate deviations from baseline patterns of circadian BP variation with the risk of AIS to select the optimal therapeutic intervention. Design and method: To complete our study, we systematically reviewed the literature from 1990-2022 through electronic medical databases (MEDLINE, Scopus and Cochrane). Results: During the nighttime hours, BP drops 10 - 20% in normotensive and untreated hypertensive patients - a dipping phenomenon, followed by a rapid and gradual increase during waking hours. In the studies being reviewed, patients were classified according to the rate of fall in systolic BP during 24-hour recording into four categories: the extreme-dippers drop >20%, dippers drop >10% and <20%, non-dippers drop <10% and >0%, and reverse-dippers or risers drop <0%. Deviating from standard dipping patterns is associated with an increased risk of AIS and highlights the value of chronotherapy, whereas no significant difference is observed in stroke prognosis. The extreme-dipping phenomenon is associated with the occurrence of ischemic stroke (IS), either due to under-treatment or due to subsequent morning hypertensive spike, whereas aggressive antihypertensive treatment seems to be significantly responsible. Interestingly, the occurrence of microbleeds in IS territory has been strongly associated with the reverse-dipping pattern. Conclusions: Overnight BP variation is an independent and robust predictor of cardiovascular risk, including AIS. Nocturnal BP may constitute a therapeutic target for the prevention of AIS. However, the available data on the effect of antihypertensive drugs and the implementation of chronotherapy with pre-sleep medication are conflicting in terms of improving cardiovascular risk. Therefore, at present, current guidelines for the treatment of BP do not recommend the aforementioned therapeutic approach as the best treatment in day-to-day clinical practice. More extensive and targeted studies are needed in the future to confirm the potential benefits of the application of chronotherapy in the prevention of AIS.