IJCS | Volume 32, Nº6, November / December 2019

616 Escosteguy et al. Temperature variation in blood pressure Int J Cardiovasc Sci. 2019;32(6):615-622 Original Article during winter and that blood pressure decreases in summer due to blood vessel dilation, associatedwith loss of salt and water through perspiration, so that lower BP values are recorded during that season. Considering that the city of Porto Alegre, capital of the state of Rio Grande do Sul, Brazil, is characterized by quite different climatic conditions during the year, the aim of the present study was to verify the correlation between the seasonal variation of temperature and relative humidity of the air during the year 2016 and the systemic arterial pressure variation in a sample assessed through ambulatory blood pressure monitoring (ABPM) of 902 patients from a private Cardiology Service of the aforementioned city. Methods This was a retrospective longitudinal study of a convenience sample, in which we analyzed 902 results of patients submitted to ABPM, after indication of their attending physicians, from January to December 2016, in a private Cardiology Service in the city of Porto Alegre/RS. The sample consisted of individuals older than 18 years of age, of both genders, divided into three groups: the first group included all 902 patients in the sample; the second group included 186 patients using one or more antihypertensive drugs of different classes, and the third group included 716 patients who did not use any type of antihypertensive medication. We analyzed the diagnostic and follow-up examinations of all patients who underwent ABPM at the clinic during the specified period. ACardios ABPMdevice was used. The values ​for systolic and diastolic blood pressure levels were obtained from the respective ABPM of each individual, and the daily values for temperature and relative humidity of the air were obtained from INMET (National Institute of Meteorology) website from December to January 2016 and were divided by the four seasons of the year (summer, fall, winter and spring). Statistical analysis The collected data were organized into a database using the software Statistical Package for Social Sciences (SPSS). 22 For the continuous variables, mean, standard deviation and 95%confidence intervals were used, as well as minimum and maximum values of each variable after assessment of their normality using the Shapiro-Wilks test. Pearson’s Correlation Coefficient was applied to correlate the mean awake systolic and diastolic blood pressure (MASBP/MADBP) and the mean resting systolic and diastolic blood pressure (MRSBP/MRDBP), minimum (MIN SBP) andmaximum (MAX SBP) systolic blood pressure, 24-hour mean systolic and diastolic blood pressure (24HMSBP/24HMDBP), systolic and diastolic dipping in relation to theminimum, mean andmaximum temperature values, and relative humidity of the air stratified by the users of antihypertensive medication (Table 2) or non-use of medication (Table 3). The analysis of variance (one-way ANOVA) was applied to compare the levels of SBP obtained in ABPM, age, temperature and relative humidity between the 4 seasons of the year 2016. For statistical significance, an alpha error < 0.05 and a 95% confidence interval were admitted. Results The results of 902 ABPM from different individuals were included in the study. The data obtained regarding the mean, standard deviation and 95% confidence interval, as well as minimum and maximum values of the patient’s age, the results related to the systolic and diastolic blood pressure levels, temperature and relative humidity are shown in Table 1. No significant associations were found when the variables obtained through ABPM were correlated with the minimum, mean and maximum values of temperature and relative air humidity, both in group 2, which used antihypertensive medications and in group 3, which did not use antihypertensive medications (Table 2 and Table 3, respectively). Also, no significant differences were found when all three patient groups (total of patients, users and non-users of antihypertensive drugs) were compared with each of the continuous obtained variables – age, minimum, mean and maximum values ​of MASBP, MADBP, MRSBP, MRDBP, MIN SBP, MAX SBP, 24HMSBP, 24HMDBP, systolic and diastolic dipping, temperature and relative humidity (Table 4) (Figures 1 and 2). Discussion Hypertension is an important factor for cardiovascular morbidity and mortality, being an independent risk factor for myocardial infarction, chronic kidney disease,