Seasonal variability in exercise test responses in Ghana

Abstract

Exercise-induced bronchospasm (EIB) is widely used in epidemiological studies to investigate the prevalence of asthma. We aimed to determine seasonal variations in the prevalence of EIB in Ghanaian school children from urban-rich (UR), urban-poor (UP), and rural (R) schools. We have previously reported the prevalence of EIB in 9-16-year-old children to be 3.1% in the dry season, with UR children having a significantly higher prevalence of both EIB and atopy compared to UP or R children. In the current study, the prevalence of EIB was assessed in the same 1,095 children in the wet season (5 months following the initial study) using the same methodology. Exercise provocation consisted of free running outdoors for 6 min. In the wet season, 17/1,095 children [mean 1.55%, 95% confidence interval (CI): 0.91-2.47] had a positive response to exercise, compared to our previous report of 34 children (mean 3.1%, 95% CI: 2.15-4.32) with EIB in the dry season (dry vs. wet season, difference 1.55, 95% CI: 0.41-2.69). The proportion of children with a positive response to exercise in the UR school fell from 4.2% (25/599) to 1.3% (8/599) (difference 2.9, 95% CI: 1.2-4.5). In the wet season, there was no difference in the prevalence of EIB among the UR, UP, and R children. Only five of 1,095 subjects (mean 0.5%, 95% CI: 0.15-1.07) demonstrated EIB in both seasons. In conclusion, although exercise challenge remains a useful tool for determining asthma prevalence in epidemiological studies, seasonal variations in the pattern of responses may occur and the results should be interpreted with caution.

Differences in both prevalence and titre of specific immunoglobulin E among children with asthma in affluent and poor communities within a large town in Ghana

“…In contrast, all but one child with documented EIB were classified as cases. Such a discrepancy between the two could reflect either an over-diagnosis of asthma in the population or the fact that exercise challenge results are influenced by poor expiratory effort, and can be reduced by environmental factors including air temperature or humidity [16]. …”

“…Five and 8 min following exercise, PEFR was again measured and the lower of the two readings recorded. Based on previously established criteria [1, 10, 16], EIB was defined as >12.5% reduction in PEFR following exercise challenge.…”

Association of air humidity with incidence of exercise‐induced bronchoconstriction in children

“…[22][23][24][25][26] However, there are only two studies assessing the relation between probability of EIB and outdoor conditions during free running test. One study in children from Ghana using peak expiratory flow rate measurements showed more EIB reactions during dry season than wet season, 27 and another study from Finland showed partial correlation between the change in R5 measured with IOS and outdoor temperature. 11 Absolute humidity (AH) is the mass of water vapor divided by the mass of dry air in a volume of air at a given temperature.…”

“…The previous studies assessing the relation between physical properties of inhaled air and probability of EIB have not consistently taken into account temperature and both AH and RH. 11,[22][23][24][25][27][28][29] These three factors are closely related ( Figure SE1), and their relative importance in provoking EIB is not known.…”

Exercise‐induced bronchospasm related to different phenotypes of rhinitis without asthma in primary schoolchildren: the French Six Cities Study

“…This low prevalence may be explained, first, by recent, substantial changes in treatment, with the use of inhaled bronchial and nasal corticosteroids , which decrease the occurrence of EIB and may protect asthmatic children from non‐specific BHR, and, second, by the exclusion of children who were unable to attain 70% of the PEFR predicted and who had used bronchodilators or other antiasthma drugs in the 48 h preceding the test. Thirdly, seasonal variability in the pattern of response may occur, as observed in Ghana (4.2% in the dry season vs. 1.3% in the wet season in urban rich children). As shown in Table , the prevalence of EIB was highest in winter, when the air was dry and cold.…”