Table 2

Ecological negative binomial regression of chronic airflow obstruction against log(GNI), smoking and log(PM_2.5), by sex

Variable	men			women
Variable	Rate ratio	95% CI	P value	Rate ratio	95% CI	P value
Smoking	4.17	2.40 to 7.26	<0.001	11.3	5.64 to 22.6	<0.001
Log(GNI)	0.90	0.81 to 0.99	0.04	0.83	0.73 to 0.94	0.003
Log(PM_2.5)	0.92	0.78 to 1.07	0.28	1.05	0.89 to 1.25	0.55

GNI, gross national income; ; PM2.5, particulate matter <2.5µm aerodynamic diameter.