Mortality risks in different subtypes of masked hypertension in the Spanish ambulatory blood pressure monitoring registry.

Objective: We aimed to evaluate the risks of death and cardiovascular death of different subtypes of masked hypertension, defined by either isolated daytime or nighttime blood pressure (BP) elevation, or both, compared with patients with normal both office and 24-h BP.

Methods: We selected 4999 patients with masked hypertension (normal office BP and elevated 24-h BP). They were divided in three different categories: isolated daytime masked hypertension (elevated daytime BP and normal nighttime BP, 800 patients), isolated nighttime masked hypertension (elevated nighttime BP and normal daytime BP, 1069 patients) and daytime and nighttime masked hypertension (elevation of both daytime and nighttime BP, 2989). All-cause and cardiovascular death (median follow-up 9.7 years) were assessed in each of these subtypes in comparison to 10 006 patients with normal both office and 24-h BP. Hazard ratios from Cox models after adjustment for clinical confounders were used for such comparisons.

Results: Compared with patients with normal both office and 24-h BP, isolated daytime masked hypertension was not associated with an increased risk of death in models adjusted for clinical confounders [hazard ratio 1.07; 95% confidence interval (CI): 0.80-1.43]. In contrast, isolated nighttime masked hypertension (hazard ratio: 1.39; 95% CI 1.19-1.63) and daytime and nighttime masked hypertension (hazard ratio: 1.22; 95% CI 1.08-1.37) had an increased risk of death in comparison to patients with BP in the normal range. Similar results were observed for cardiovascular death.

Conclusion: The risk of death in masked hypertension is not homogeneous and requires nocturnal BP elevation, either isolated or with daytime elevation. Isolated daytime masked hypertension is not associated with an increased risk of death.