Table 1.
Candidate prognostic factors for participants included in the study (n = 3657)
| Variables | Coding for analysis | |
|---|---|---|
| Age, mean (SD) | 66.5 (8.6) | Continuous |
| Sex, female, n (%) | 2687 (73%) | Categorical |
| BMI, kg/m2, mean (SD) | 26.9 (4.7) | Continuous |
| Current smoking, n (%) | 353 (9.7%) | Categorical |
| Living alone, n (%) | 1006 (28%) | Categorical |
| Sick leave due to hip problems for more than one month during the past 12 months, n (%) | 93 (2.5%) | Categorical |
|
Educational level, n (%) Primary and lower secondary school (9–10 years) Higher general examination program (12-13 years) Short-cycle higher education (less than three years more) Medium-cycle higher education (three to four years more) Long-cycle higher education (minimum five years more) |
620 (17%) 372 (10%) 665 (18%) 1550 (42%) 450 (12%) |
Categorical |
|
Employment, n (%) Employed/student Unemployed Retired Self-imposed early retirement Early retirement due to low ability to work On sick leave full time or part time |
1026 (28%) 49 (1.3%) 2131 (58%) 222 (6.1%) 119 (3.3%) 110 (3.0%) |
Categorical Collapsed as either “no” regardless of what kind of retirement or “yes” regardless of current sick leave or temporary unemployment. |
|
Self-reported radiographic OA, n (%) Had x-ray with radiographic OA Had x-ray without radiographic OA Had no x-ray or do not know |
3007 (82%) 131 (3.6%) 519 (14%) |
Categorical Collapsed as either “present” (had x-ray with radiographic OA) or “absent” (had x-ray with no radiographic OA, had no x-ray or do not know). |
| Wait-listed for THR of the index hip, n (%) | 100 (2.7%) | Categorical |
| Joint replacement in the other hip or knees, n (%) | 362 (9.9%) | Categorical |
|
Comorbidities, n (%) None One Two Three or more |
1425 (39%) 1321 (36%) 616 (17%) 295 (8%) |
Categorical |
|
Pain medication the last 3 months, n (%) No use of pain medication Has used only paracetamol/acetaminophen and/or NSAID Has used opioids (everyone using opioids also used paracetamol/acetaminophen and/or NSAID) |
1308 (36%) 2033 (56%) 316 (8.6%) |
Categorical: Collapsed into pain medication usage in the past 3 months “yes” (used paracetamol, acetaminophen, NSAID or opioids) or “no” (did not use any type of pain medication) |
| Fear of joint damage from physical activity, n (%) | 365 (10%) | Categorical |
| Bilateral hip symptoms, n (%) | 946 (26%) | Categorical |
| Number of painful areas during the last 24 h (0–56 areas market on a body chart front and rear view), median (IQR) | 3 (3) | Continuous |
| Hip pain (average) during the last month (VAS 0–100), median (IQR) | 48 (21) | Continuous |
| Duration of symptoms in the index joint, months (n = 2770), median (IQR) | 24 (40) | Not included as a prognostic factor |
| UCLA activity score (1–10), median (IQR) | 6 (3) |
Categorical: In the analysis, the original 10 categories were collapsed into 5 |
| HOOS quality of life subscale score, median (IQR) (0–100) | 50 (19) | Continuous |
| Self-Efficacy (ASES) median (IQR) (10–100) | 68 (26) | Continuous |
| Health-related quality of life (EQ-5D-5L), median (IQR) (− 0.624 to 1) | 0.723 (0.110) | Continuous |
| 40 m walk test (m/s), median (IQR) | 1.49 (0.43) | Continuous |
| 30 s chair stand test (no. of rises), median (IQR) | 12 (5) | Continuous |
UCLA, University of California, Los Angeles Physical Activity Scale (1–10). Level 10 is very high and 1 is very low. HOOS QoL, Hip disability and Osteoarthritis Outcome Score, the quality-of-life subscale score (0–100 worst to best).
ASES, Arthritis Self-Efficacy Scale. Only subscales for pain and other symptoms were collected and a mean were calculated. Higher scores indicate higher self-efficacy. EQ-5D-5L, The EuroQoL 5-Dimensions 5-Level questionnaire presented as an index value scored using the Danish crosswalk value set