Figure 2.

Differences in exacerbation frequency across GOLD stages. Red, classic CB⁺ vs classic CB^–; blue, SGRQ CB⁺ vs SGRQ CB^–. Circles represent mean difference and error bars represent 95% CI. *P < .05 and †P < .0001 compared with classic CB^– or SGRQ CB^–, respectively, on multivariable linear regression. CB = chronic bronchitis; GOLD = Global Initiative for Chronic Obstructive Lung Disease. See Figure 1 legend for expansion of other abbreviation.