s stratified into subsets in which the effects of daily average temperature on BP were estimated separately. In that process, there seemed to be a linear 
trend in the medication categories but not for the age categories. As the medication of benazepril continued, the impact of temperature on SBP decreased. The fluctuation of SBP with temperature in the three years was 11.9, 8.1 and 4.9 mmHg respectively. In the DBP model, similar medication-temperature interactions existed. The gender-temperature, drinking-temperature, and BMI-temperature interactions were all significant. The regression coefficient of the medication- temperature interaction was 0.00084, so the change in DBP to the ambient temperature change was estimated to decrease by 1.3 mmHg each year. When stratified by medication duration the effect of temperature also decreased. The Linear regression was used to investigate the association between the average baseline BP of patients recruited in the same week and the mean of weekly ambient temperature. Significant inverse correlations were found for SBP, as well as DBP. The average temperature 10463589 explained 32.4% and 65.6% of the variation of SBP and DBP, respectively. To investigate the BP fluctuation of the same subjects as temperature changes, the temperature-BP relationship was also examined in the three-year follow-up dataset. Similar linear regression was implemented except that duration of benazepril medication was included to represent the effect of antihypertensive therapy. In the follow-up R-7128 price models without duration of benazepril medication, the average temperature accounted for 39.2% and 39.0% of BP variation. The full follow-up models explained 86.5% and 88.4% of SBP and DBP variation. To further confirm the 21821671 fluctuation of BP with temperature, subsets of patients recruited around October and February, when the ambient temperatures were highest and lowest in the year of recruitment, were selected separately to investigate the trends. These two groups showed opposite BP trends: at around the 50th, the 100th and the 150th week, BP of the first group reached its lowest, while the second group was at its highest. To exclude the potential influence of dihydrochlorothiazide on the results, the analyses were repeated in a dataset without the 57 subjects involved, and the results did not appreciably change. The association of daily average ambient temperature and blood pressure were examined with multilevel model, adjusted for other factors listed in the table. SBP indicates systolic blood pressure; DBP, diastolic blood pressure; BMI, body mass index. a Significant in the SBP model. b Significant in the DBP model. doi:10.1371/journal.pone.0084522.t002 hypertension, and raise public health concerns. Also, it may help explain the increased mortality of cardiovascular diseases in cold seasons. It has long been noted that BP varies in different seasons, and some studies have been conducted to examine 4 Ambient Temperature, Blood Pressure and Regulators conditioning may therefore reduce the reliability of the ambient temperature’s effect. Portable tracking device of temperature would be an optimal solution for future studies. We also investigated there are factors that modify the association of ambient temperature and BP. Alperovitch examined the interaction between antihypertensive medication and temperature, but their subjects were taking several kinds of drugs and the researchers did not find significant differences. In our study, we
