WINTER SUMMER DIFFERENCES IN THE EFFECTS OF EMOTION, POSTURE AND PLACE OF MEASUREMENT ON BLOOD-PRESSURE

The purpose of this study was to assess whether the effects of emotional state, posture, situation of measurement, and sex on daily blood pressure variation were different in subjects measured during summer months (May-September) and winter months (November-March). The subjects of the study were 157 patients from the Hypertension Center of New York Hospital-Cornell Medical Center in New York, who had ambulatory blood pressure monitoring performed between February 1984 and April 1985. Individual pressures taken with the monitor over the day in each subject were transformed to z-scores using the subject's daily mean pressure and standard deviation in order to assess differences in intraindividual variation. The z-scores were examined in separate but identical analyses of variance models (one for the winter months and one for the summer months) which included emotional state (happy, angry, anxious), posture (sitting, standing), situation of measurement (home, work, elsewhere) and sex as factors. The results showed that more factors had greater effects (as reflected in R2) on blood pressure during the winter months than summer months. In particular, the relative effect of anxiety, sitting, and being at work or home on blood pressure was significantly greater (P < 0.05) in the winter months than summer months. In addition, pressure elevation during happiness was also more accentuated in winter than summer for diastolic pressure (P < 0.05). These findings may have important implications for the interpretation of population studies examining the relationship between blood pressure and psychosocial stressors. © 1990.