. Author manuscript; available in PMC: 2010 Apr 24.

Published in final edited form as: Thorax. 2009 Apr 8;64(8):698–704. doi: 10.1136/thx.2008.111278

Table 2.

The distribution of demographic characteristics for NETT COPD cases and NAS controls.

Demographic Characteristics^*	NETT (n = 389)	NAS (n = 420)	p-value
Age (years)	67 ± 6	68 ± 9	0.9
Pack-years	66 ± 30	39 ± 27	<0.001
FEV₁ (% predicted, post BD)^†	28 ± 7	92 ± 11
Modified BODE score (median ± IQR)^‡	5 ± 3	NA
Gender (% male)	64%	100%

Values are ± standard deviation unless otherwise listed

^†

FEV₁ % predicted values for the NETT and NAS are based on the prediction equations of Crapo and Morris (47); however the NAS-1988 standards were used in the selection of the control group.

^‡

Modified BODE score incorporates the University of San Diego Shortness of Breath Questionnaire, IQR = interquartile range