Relationship of respiratory symptoms and climatic seasonality at an out-patient primary health unit in Brazil

Brazilian studies have documented an association of humidity with an increase in the proportion of respiratory symptoms. However, they were based on secondary data, raising concerns of validity and reliability. The goal of this study was to evaluate the relationship between the climatic seasonality and the proportion of respiratory symptoms on subjects attending an out-patient primary health unit during each season at a Brazilian city with tropical weather. It was a cross-sectional study on subjects attending an primary health unit in relation to meteorological data daily collected. During one year, 48 observations divided by season were made. Among 3409 subjects, 15% presented with respiratory symptoms. This paper identifies the association of low levels of humidity and precipitation coinciding with an increase in the number of subjects with respiratory symptoms on winter. ANOVA test shows a significant difference between winter and spring (p=0.02).There was significant negative correlation between the number of patients with respiratory symptoms and the mean of previous three days minimum relative humidity (p=0.002). An ARMAX model shows a statistically significant coefficient (p>0.0001). These findings suggest that at a Brazilian city with tropical weather, the proportion of respiratory symptoms on subjects attending a primary health unit is increased with the reduction of relative air humidity.