Short-term exposure to fine particulate matter and asthma exacerbation: a large population-based case-crossover study in Southern Thailand

Table 1 Characteristics of asthma patients

Variable	N (%)
Sex
Male	1,327 (37.9%)
Female	2,177 (62.1%)
Age group at outpatient visits (years)*
6–11	2,740 (5.3%)
12–17	1,309 (2.5%)
18–44	9,399 (18.2%)
45–64	18,290 (35.4%)
≥ 65	19,920 (38.6%)
Viral infection status at outpatient visits*
Detected	67 (0.1%)
Not detected	768 (1.5%)

* Since asthma exacerbations may recur, individuals can be counted multiple times during outpatient visits

ISSN: 1476-069X