• Ramón C Hermida, Diana E Ayala, Artemio Mojón, and José R Fernández.
• Bioengineering and Chronobiology Laboratories, University of Vigo, Campus Universitario, Vigo, Pontevedra, Spain. rhermida@uvigo.es
• Chronobiol. Int. 2013 Mar 1; 30 (1-2): 328-39.

AbstractSeveral previous studies found that too great a reduction of clinic blood pressure (BP) by treatment increased cardiovascular disease (CVD) risk, whereas moderate reduction decreased it. Thus, it has been suggested that the relationship between BP and CVD events is J-shaped, with CVD risk decreasing as BP is lowered, and then rising as BP is further decreased. Correlation between BP level and CVD risk, however, is stronger for ambulatory BP monitoring (ABPM) than clinical BP measurements. We previously established that the hypertension treatment-time regimen, upon awakening versus at bedtime, exerts differential effect on BP control during the day and nighttime, which translates into a differential degree of CVD risk prevention. We, therefore, investigated the role of hypertension treatment-time scheme on the nature of the relationship between achieved clinic and ambulatory BP and CVD risk in the MAPEC (Monitorización Ambulatoria para Predicción de Eventos Cardiovasculares, i.e., Ambulatory Blood Pressure Monitoring for Prediction of Cardiovascular Events) study, a prospective, open-label, blinded-endpoint trial on 2156 hypertensive patients (1044 men/1112 women), 55.6 ± 13.6 (mean ± SD) yrs of age, randomized to ingest all prescribed once-a-day hypertension medications upon awakening or the entire daily dose of ≥1 of them at bedtime. Ambulatory BP was measured for 48-h at baseline and annually thereafter, and more frequently (quarterly) when adjustment of treatment was necessary. After a median follow-up of 5.6 yrs, a J-shaped relationship was detected between total CVD events and clinic as well as awake BP mean, but only for the group of patients ingesting all medications upon awakening. The relationship was different in the group of patients who ingested ≥1 medications at bedtime; the risk of CVD events progressively diminished in a linear, rather than J-shaped, manner with treatment-induced decrease in awake BP mean. The adjusted hazard ratio of CVD events was significantly lower with the progressive reduction in the asleep BP mean, independent of the hypertension treatment-time regimen. There was no single major event, i.e., CVD death, myocardial infarction, or stroke, in patients who achieved an asleep systolic BP mean <103 mm Hg. Our findings indicate that bedtime hypertension treatment is not associated with a J-shaped relationship between achieved BP and CVD risk. The decreased CVD risk associated with the progressive reduction in asleep BP, more feasible by bedtime than morning hypertension treatment, has clinical implications, in particular, the need to consider the proper timing of hypertension medications, in conjunction with ABPM for proper assessment of BP control, as an improved and potentially safer means of reducing CVD risk of hypertensive patients.

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