Seasonal variation in meteorological parameters and office, ambulatory and home blood pressure: predicting factors and clinical implications.

This study investigated the relationship between seasonal variations in blood pressure (BP) and the corresponding changes in meteorological parameters and weather-induced patients' discomfort. Hypertensives on stable treatment were assessed in winter-1, summer and winter-2 with clinic (CBP), home (HBP) and 24-hour ambulatory BP (ABP). Discomfort indices derived from temperature, humidity and atmospheric pressure that reflected subjects' discomfort were evaluated. Symptomatic orthostatic hypotension was assessed with a questionnaire. Sixty subjects (mean age 65.1±8.8 [s.d.], 39 men) were analyzed. CBP, HBP and daytime ABP were lower in summer than in winter (P<0.01). Nighttime ABP was unchanged, which resulted in a 55% higher proportion of non-dippers (P<0.001). All the discomfort indices that reflected weather-induced subjects' discomfort were higher in summer (P<0.05) and systolic daytime ABP was <110 mm Hg in 15 subjects (25%). Seasonal changes in temperature and the discomfort indices were correlated with BP changes (P<0.05). Multivariate analyses revealed that winter BP levels, seasonal differences in temperature, female gender and the use of diuretics predicted the summer BP decline. In conclusion, all aspects of the BP profile, except nighttime ABP, are reduced in summer, resulting in an increased prevalence of non-dippers in summer with unknown consequences. Seasonal BP changes are influenced by changes in meteorological parameters, anthropometric and treatment characteristics. Trials are urgently needed to evaluate the clinical relevance of excessive BP decline in summer and management guidelines for practicing physicians should be developed.