Table 3.
Income as a determinant of watts in CPET, adjusted for age, sex, Post FEV1% predicted, mMRC, loneliness, married status, smoking pack years and education beyond high school.
| Variables | DF | Parameter estimates | Standard error | t Value | Pr > |t| |
|---|---|---|---|---|---|
| Intercept | 1 | 48.24 | 5.99 | 8.06 | <0.0001 |
| Married | 1 | 1.79 | 1.16 | 1.55 | 0.1222 |
| Lonely or isolateda | 1 | −0.48 | 1.85 | −0.26 | 0.7957 |
| Income < US$30,000 | 1 | −2.27 | 1.11 | −2.04 | 0.0419 |
| Age | 1 | −0.77 | 0.08 | −9.14 | <.0001 |
| Sex, male | 1 | 22.14 | 1.12 | 19.83 | <0.0001 |
| Post BD FEV1% predicted | 1 | 1.36 | 0.07 | 18.60 | <0.0001 |
| MMRC | 1 | −2.88 | 0.54 | −5.34 | <0.0001 |
| Education beyond high schoolb | 1 | 2.14 | 1.05 | 2.04 | 0.0417 |
| Smoking pack years | 1 | 0.01 | 0.02 | 0.47 | 0.6416 |
DF: degrees of freedom; Pr > |t|: t-test significance level; Post BD FEV1% pred: postbronchodilator forced expiratory volume in 1 second; MMRC: Modified medical research council scale. Every value in italics <0.05 denotes significance (standard practice).
aLoneliness and isolation was measured by asking subjects “Do you feel lonely or socially isolated now or in the last 3 days?”. An answer was either “yes” or “no.”20
bEducation was determined by dividing patients into two groups: those who had education levels beyond high school and those who did not.