A synoptic approach to weather conditions discloses a relationship with ambulatory blood pressure in hypertensives.

Background: Higher blood pressure (BP) values in cold than in hot months has been documented in healthy and hypertensive adults. These changes may potentially contribute to the observed excess winter cardiovascular mortality in the general population. However, the effects of weather have always been investigated by considering the effects of a single variable rather than considering the combination of ground weather variables characterizing a specific weather pattern (air mass). Methods: We retrospectively investigate the relationship between BP and specific air masses in hypertensive subjects (n=540) referred to our Hypertension Unit for 24-h ambulatory BP monitoring during the period of the year characterized by the highest weather variability (winter). Five different winter daily air masses were classified according to the combination of ground weather data (air temperature, cloud cover, relative humidity, atmospheric pressure, wind speed and direction). Results: Multivariate analysis selected the air mass as a significant predictor of mean 24-h BP (p<0.01 for DBP and p<0.05 for SBP), daytime DBP (p<0.05) and nighttime BP (p<0.01 for both SBP and DBP), with higher BP values observed in cyclonic than in anticyclonic days. When the effects of a two-day sequences of air masses was considered an increase in ambulatory BP followed a sudden day-to-day change of weather pattern going from settled, cloudless and cold days, to perturbed, cloudy and mild days. Conclusion: The weather may affect BP particularly in the elderly. The forecast of a sudden change of air mass could thus provide important information especially helpful for hypertensive people during winter.