TABLE 1 Characteristics of the chronic obstructive pulmonary disease (COPD) and non-COPD populations

Characteristic	COPD population	Non-COPD population	p-value^#
Subjects n (%)	909 948 (12.6)	6 331 643 (87.4)
Age years mean±sd	64.3±13.8	53.4±13.3	<0.001
Females	50.4	52.2	<0.001
Socioeconomic status
Quintile 1^¶	23.4	18.0	<0.001
Quintile 2	21.8	19.4
Quintile 3	19.4	19.9
Quintile 4	18.4	21.0
Quintile 5⁺	16.7	21.5
Rural^§	16.2	11.9	<0.001
Asthma	26.9	8.3	<0.001
Deaths^ƒ	14.6	3.3	<0.001

^#: testing the hypothesis of no difference between the COPD and non-COPD populations; ^¶: lowest; ⁺: highest; ^§: versus urban; ^ƒ: accumulated mortality rate at 4 years.