Isolated nocturnal hypertension and subclinical target organ damage: a systematic review of the literature

Isolated nocturnal hypertension (INH) is associated with greater mortality and cardiovascular events. Subclinical target organ damage (TOD) is a prognostic marker for cardiovascular events. Our objective is to systematically summarize evidence on the association between INH and subclinical TOD. Observational population studies were considered. INH was defined as nighttime blood pressure (BP) ⩾120 and/or 70 mm Hg with daytime BP <135/85 mm Hg. We systematically searched Pubmed, EMBASE and the Cochrane Library. Abstracts were reviewed by two assessors. Potentially eligible articles were compared with inclusion criteria. The search yielded 954 titles, 13 abstracts were selected for review and four articles fulfilled inclusion criteria. INH was associated with higher ambulatory arterial stiffness index (0.4 unit vs. 0.35 unit, P<0.05), pulse wave velocity (16.2 m s−1vs. 14.7 m s−1, P<0.05), central (140.4% vs. 134.0%, P<0.05) and peripheral (82.6% vs. 76.5%, P<0.01) augmentation index in a Chinese study. In the same population there was no association with left ventricular hypertrophy documented by electrocardiogram. INH was not associated with increased arterial stiffness or left venticular mass index in a Swedish study. An American study demonstrated higher left ventricular mass (152.46 g vs. 136.16 g, P=0.01) and greater odds of left ventricular hypertrophy (odds ratio 3.03, 95% confidence interval 1.02–9.05) in unadjusted analysis. There was no association with proteinuria. Evidence is inconclusive regarding the association between INH and subclinical TOD. Future research should focus on trying to elucidate the mechanisms that generate INH and contribute to the higher mortality associated with this BP pattern.