Table 3.
Ordinal logistic regression models of depressed mood and anhedonia in the past 2 weeks in patients with distress from itcha
| Distress from itch | Frequency [%]b | OR (95 % CI) | P value | aOR (95 % CI) | P value | |
|---|---|---|---|---|---|---|
| Depressed mood | Not at all/several days | More than half the days/nearly every day | ||||
| No itch | 949 (87.1) | 141 (12.9) | 1.00 [reference] | – | 1.00 [reference] | – |
| A little/some | 462 (79.8) | 117 (20.2) | 1.70 (1.30–2.23) | < 0.0001 | 1.68 (1.28–2.22) | < 0.0001 |
| Quite a lot/very much | 89 (58.6) | 63 (41.5) | 4.76 (3.30–6.88) | < 0.0001 | 4.91 (3.36–7.18) | < 0.0001 |
| Anhedonia | Not at all/several days | More than half the days/nearly every day | ||||
| No itch | 907 (84.5) | 166 (15.5) | 1.00 [reference] | – | 1.00 [reference] | – |
| A little/some | 423 (75.1) | 140 (24.9) | 1.81 (1.40–2.33) | < 0.0001 | 1.77 (1.37–2.30) | < 0.0001 |
| Quite a lot/very much | 82 (54.7) | 68 (45.3) | 4.53 (3.16–6.50) | < 0.0001 | 4.46 (3.07–6.47) | < 0.0001 |
| Any depressed mood and anhedonia | Either | Both | ||||
| No itch | 267 (46.1) | 312 (53.9) | 1.00 [reference] | – | 1.00 [reference] | – |
| A little/some | 155 (39.0) | 242 (61.0) | 1.34 (1.03–1.73) | 0.03 | 1.27 (0.97–1.66) | 0.08 |
| Quite a lot/very much | 30 (23.8) | 96 (76.2) | 2.74 (1.76–4.26) | < 0.0001 | 2.81 (1.78–4.41) | < 0.0001 |
aOR adjusted odds ratio, CI confidence interval, OR odds ratio
Ordinal logistic regression models were constructed with depressed mood and anhedonia as the dependent variables (from the Patient Health Questionnaire-2) and distress from itch as the ordinal predictor. The models did not meet proportional odds assumptions (score test, P < 0.001 for both). Therefore, depressed mood and anhedonia were dichotomized into (1) not at all or several days in the past 2 weeks; or (2) more than half the days or nearly every day in the past 2 weeks. In addition, models were constructed with both depressed mood and anhedonia versus either symptom as the dependent variable. ORs and 95 % CIs were estimated. Multivariable models were constructed, which included gender (male/female); age (continuous); race/ethnicity (white, black, Hispanic, Asian/Pacific Islander, and other); and language of the interview (English/Spanish) as covariates. aORs and 95 % CIs were estimated
Missing data were encountered in 0 subjects (0.0 %) for age, gender, language, and date of interview; 85 subjects (5.4 %) for race/ethnicity; 12 subjects (0.6 %) for depressed mood or anhedonia; and 142 subjects (6.8 %) for itch in the past week