Background--The clinical significance of long-term seasonal variations in self-measured home blood pressure (BP) has not been elucidated for the cardiovascular disease prevention. Methods and Results--Eligible 2787 patients were classified into 4 groups according to the magnitude of their seasonal variation in home BP, defined as an average of all increases in home BP from summer (July-August) to winter (January- February) combined with all decreases from winter to summer throughout the follow-up period, namely inverse- (systolic/ diastolic, < 0/< 0 mm Hg), small- (0-4.8/0-2.4 mm Hg), middle- (4.8-9.1/2.4-4.5 mm Hg), or large- (≥9.1/≥4.5 mm Hg) variation groups. The overall cardiovascular risks illustrated U-shaped relationships across the groups, and hazard ratios for all cardiovascular outcomes compared with the small-variation group were 3.07 (P=0.004) and 2.02 (P=0.041) in the inversevariation group and large-variation group, respectively, based on systolic BP, and results were confirmatory for major adverse cardiovascular events. Furthermore, when the summer-winter home BP difference was evaluated among patients who experienced titration and tapering of antihypertensive drugs depending on the season, the difference was significantly smaller in the early (September-November) than in the late (December-February) titration group (3.9/1.2 mm Hg versus 7.3/ 3.1 mm Hg, P < 0.001) as well as in the early (March-May) than in the late (June-August) tapering group (4.4/2.1 mm Hg versus 7.1/3.4 mm Hg, P < 0.001). Conclusions--The small-to-middle seasonal variation in home BP (0-9.1/0-4.5 mm Hg), which may be partially attributed to earlier adjustment of antihypertensive medication, were associated with better cardiovascular outcomes.
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