A population Japanese study suggested that a diminished nighttime decline in blood pressure (BP) (non-dipper pattern) is a risk factor for cardiovascular mortality independent of the 24 h mean BP level [J Hypertens. 2002;20:2183–9]. We compared the relative influence of the BP level and the sleep-time relative BP decline as contributing factors for cardiovascular morbidity and mortality in the MAPEC study, designed to investigate whether increasing the sleep-time relative BP decline results in reduced cardiovascular risk.
This prospective study investigated 3344 subjects (1718 men), 52.6 ± 14.5 years of age. At baseline, BP was measured every 20-min from 07:00 to 23:00 h and every 30-min at night for 48 h. Subjects were classified as having elevated BP if the awake mean was >135/85 mmHg for systolic/diastolic BP or the asleep mean >120/70 mmHg, and of normal BP otherwise. The Cox proportional-hazard model was used to estimate relative risks of cardiovascular events associated to elevated BP and/or diminished sleep-time relative BP decline.
After a median time of follow-up of 5.6 years and with adjustment for significant confounding factors including gender, age, antihypertensive treatment and diabetes, the relative hazard ratio of cardiovascular events for dipper subjects with elevated BP as compared to dipper subjects with normal BP was 1.57 (95% confidence interval [1.03–2.39]; P = 0.036). Subjects with a non-dipper BP pattern had higher cardiovascular risk, whether BP was within the normotensive range (1.95 [1.33–2.87]; P < 0.001; P = 0.218 compared to dipper subjects with elevated BP) or above it (4.01 [2.89–5.56]; P < 0.001).
Cardiovascular risk is more closely related to a diminished sleep-time relative BP decline than to an elevated BP. Among subjects with BP in the normotensive range, non-dippers have twofold cardiovascular risk than dippers. Moreover, cardiovascular risk was 40% higher for non-dippers with normal BP (who would not be treated according to current guidelines) than for dippers with elevated BP. ABPM is a diagnostic technique that should be extended and recommended for proper cardiovascular risk assessment.
1University of Vigo, Vigo, Spain
2Urgencias Sanitarias 061 Galicia, Santiago, Spain