Table 4.
—Mixed-Effects Linear Regression Model for SGRQ Total Score Using Hospitalized Exacerbation Frequency in the Prior Year (N = 1,255)
| Predictor Variable and Level | Estimate | SE | P Value |
| Pack-y smoking history | 0.062 | 0.014 | < .001 |
| Age, y | −0.237 | 0.049 | < .001 |
| Hospitalized exacerbation race interaction | |||
| African American | 4.187 | 2.020 | .04 |
| Caucasian | Ref | … | … |
| Hospitalized exacerbation | 4.748 | 1.059 | < .001 |
| FEV1 % predicted | −0.117 | 0.019 | < .001 |
| Sex | |||
| Female | −1.074 | 0.711 | .13 |
| Male | Ref | … | … |
| MMRC dyspnea score | 8.760 | 0.309 | < .001 |
| Race | |||
| African American | −0.882 | 1.232 | .47 |
| Caucasian | Ref | … | … |
| 6-min walk distance, m | −0.025 | 0.004 | < .001 |
| Education level | −4.490 | 1.149 | < .001 |
| More than HS | −2.457 | 1.219 | .04 |
| Graduated HS | Ref | … | … |
| Less than HS | |||
| Current smoking | |||
| Yes | 2.585 | 0.823 | .002 |
| No | Ref | … | … |
This mixed-effects linear regression model included clinical center as a random effect to account for possible regional and other differences. Clinical center did affect SGRQ total score (P < .001). Of the 1,273 subjects in GOLD stages I to IV, six subjects did not answer the question about current smoking, and 12 subjects did not answer the questions from which MMRC dyspnea score was derived. As a result, 1,255 subjects were used in this regression analysis. See Table 1-3 legends for expansion of abbreviations.