Table 1.
Characteristics of RA cases and their matched controls and the association of HOUSES and each variable with risk of RA
| Controls (N=650) | RA cases (N=650) | Adjusted OR* (95% CI) | p Value | |
|---|---|---|---|---|
| Age at index date of RA, years, mean (SD) | 55.8 (15.7) | 55.8 (15.7) | 1.00 (0.93 to 1.07)/ 10 year increase | – |
| Gender (female): | 448 (69%) | 448 (69%) | 1.00 (0.79 to 1.27) | – |
| Year of index date, mean (SD) | 1998.6 (5.6) | 1998.6 (5.6) | 1.00 (0.82 to 1.21)/ 10 year increase | 0.97 |
| Race: Caucasian | 618 (96%) | 604 (94%) | 0.59 (0.36 to 0.99) | 0.046 |
| HOUSES | 0.002 | |||
| N | 564 | 604 | 1.06 (1.02 to 1.09)/1 unit | |
| Mean (SD) | 0.5 (3.8) | −0.2 (3.1) | decrease | |
| Median (Q1, Q3) | 0.0(−1.9, 2.4) | −0.5 (−2.1, 1.5) | ||
| HOUSES in quartiles | ||||
| Quartile 1 (lowest SES) | 130 (23) | 162 (27) | 1.04 (0.75 to 1.44) | 0.02 |
| Quartile 2 | 128 (23) | 164 (27) | 1.42 (1.02 to 1.98) | |
| Quartile 3 | 151 (27) | 141 (23) | 1.37 (0.98 to 1.91) | |
| Quartile 4 (Highest SES) | 155 (27) | 137 (23) | Referent | |
| Educational level | <0.001 | |||
| Missing | 13 | 22 | ||
| <High school | 60 (9%) | 57 (9%) | 1.92 (1.15 to 3.22) | |
| High school | 192 (30%) | 201 (32%) | 2.13 (1.41 to 3.20) | |
| Technical-school/college | 292 (46%) | 324 (52%) | 2.28 (1.54 to 3.37) | |
| Graduate school | 93 (15%) | 46 (7%) | 1 (reference) | |
| Married in lifetime | 581 (90%) | 590 (91%) | 1.20 (0.82 to 1.74) | 0.35 |
| Body mass index | 0.46 | |||
| Underweight <18.5 kg/m2 | 7 (1%) | 13 (2%) | 1.92 (0.75 to 4.95) | |
| Normal ≥18.5–24.9 kg/m2 | 213 (33%) | 208 (32%) | 1 (reference) | |
| Overweight ≥25–29.9 kg/m2 | 225 (35%) | 212 (33%) | 0.96 (0.73 to 1.26) | |
| Obesity ≥30 kg/m2 | 204 (31%) | 216 (33%) | 1.09 (0.82 to 1.43) | |
| Smoking status | 0.015 | |||
| Current | 104 (16%) | 120 (18%) | 1.36 (1.00 to 1.84) | |
| Former | 194 (30%) | 229 (35%) | 1.41 (1.09 to 1.81) | |
| Never | 352 (54%) | 301 (46%) | 1 (reference) | |
| Pertinent comorbidities | ||||
| Diabetes mellitus | 56 (9%) | 61 (9%) | 1.10 (0.75 to 1.62) | 0.62 |
| Congestive heart failure | 19 (3%) | 17 (3%) | 0.89 (0.45 to 1.75) | 0.73 |
| Alcohol misuse | 42 (6%) | 43 (7%) | 1.03 (0.66 to 1.60) | 0.91 |
| Hypertension | 337 (52%) | 412 (63%) | 1.82 (1.42 to 2.34) | <0.001 |
| Hyperlipidaemia | 348 (54%) | 373 (57%) | 1.20 (0.95 to 1.51) | 0.14 |
| Charlson comorbidity index† | <0.001 | |||
| 0 | 429 (66%) | 259 (40%) | 1 (reference) | |
| 1–2 | 150 (23%) | 281 (43%) | 3.20 (2.46 to 4.17) | |
| ≥3 | 71 (11%) | 110 (17%) | 2.61 (1.79 to 3.18) |
*Adjusted for age, gender and calendar year of RA incidence/index date.
†Excluding rheumatological disorders for comparability.
HOUSES, HOUsing-based index of socioeconomic status; RA, rheumatoid arthritis.