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 |