Excess of children's outpatient consultations due to asthma and bronchitis and the association between meteorological variables in Canoas City, Southern Brazil.

The southern Brazilian city of Canoas, situated in the metropolitan region of Porto Alegre, is subject to several annual meteorological phenomena, such as cold fronts and squall lines. Here, we assess the relationship between meteorological conditions and outpatient consultations for asthma or bronchitis in children from Canoas City. Data from outpatient consultations of children (below 9 years), between January/2005 and September/2008, were combined with daily meteorological data from 12UTC (morning) and 18UTC (afternoon). We identified 42 days with an excess of outpatient consultations (peaks). Consultations were negatively correlated with temperature and human thermal comfort index (HTCI) from the 3 previous days based on consultation data at 12 and 18UTC, and positively correlated with atmospheric pressure. A positive correlation with relative humidity was significant only at 12UTC. The highest correlations occurred on the day of consultation (12UTC) with temperature, relative humidity, and atmospheric pressure, as well as 2 days previous to the HTCI. The sensation of cold was associated with about 55% of the days of the period at 12UTC: considering only the peaks of consultations, this association exceeds 90% of days. The highest frequencies of respiratory complications (June, July, and August) were associated with negative temperature anomalies, wind speed and direction, and positive anomalies in relative humidity and atmospheric pressure. Nearly half (45%) of the air masses associated with respiratory complications arrived at Canoas from a SW direction, 19% from the south and 14% from the west. In summary, observed increases in respiratory complications were mainly associated with the presence of cold and humid air (and/or falling temperature with increasing humidity) in the morning.