Table 2.

Poisson and negative binomial regression analyses of ambient PM2.5 and weekly RTD-related outpatient visits

Outcome category	Outcome	Model	IRR per 10 µg/m³ increase in PM2.5 (95% CI)	p-value
Respiratory Tract Diseases (RTDs)a	Total RTD-related outpatient visits	Negative binomial	1.139 (1.059,1.225)	< 0.001*
	Common cold	Negative binomial	1.164 (1.082,1.252)	< 0.001*
	Allergic rhinitis	Negative binomial	1.240 (1.126,1.365)	< 0.001*
	Acute laryngitis	Negative binomial	0.923 (0.509,1.671)	0.79
	Sinusitis	Poisson	1.168 (1.017,1.342)	0.028*
	Epistaxis	Poisson	1.182 (0.734,1.904)	0.492
	Bronchitis	Poisson	1.009 (0.867,1.174)	0.909
	Asthma	Poisson	1.429 (1.003,2.037)	0.048*
	Influenza	Negative binomial	0.981 (0.953,1.010)	0.200
	Pneumonia	Poisson	0.719 (0.379,1.365)	0.314
	Othersb	Poisson	0.971 (0.817,1.155)	0.742
Respiratory Tract Symptoms (RTSs)	Shortness of breath	Poisson	1.234 (1.018,1.494)	0.032*
	Sore throat	Negative binomial	1.115 (1.027,1.211)	0.010*
	Epistaxis	Poisson	1.149 (0.799,1.651)	0.454
	Fever	Negative binomial	0.981 (0.863,1.115)	0.765
	Cough	Negative binomial	1.112 (1.014,1.220)	0.024*
	Phlegm	Negative binomial	1.135 (1.019,1.264)	0.022*
	Sneezing	Negative binomial	1.184 (1.099,1.276)	< 0.001*
	Eye/ear symptoms	Poisson	1.212 (1.028,1.429)	0.022*
	Hoarseness	Negative binomial	0.923 (0.509,1.671)	0.790

^aRTD categories were classified according to ICD-10 codes, including acute upper respiratory infections (J00–J06), allergic rhinitis (J30–J31), sinusitis (J01–J32), acute laryngitis (J04), bronchitis (J20–J40), asthma (J45–J46), influenza (J09–J11), and pneumonia (J12–J18)

^bOther respiratory diagnoses included cough (R05), abnormalities of breathing (R06), pain in throat and chest (R07), nasal polyp (J33), other disorders of the nose and nasal sinuses (J34), diseases of vocal cords and larynx (J38), and other respiratory disorders (J98)

*p ≤ 0.05