Univariate associations with RA-related autoimmunity in the SERA case-control study, 2002–07.
| Characteristic | Cases, n = 76 | Controls, n = 154 | Unadjusted OR*, (95% CI) | p |
|---|---|---|---|---|
| 25,OH vitamin D level, mean (SD) | 26.89 (10.04) | 25.30 (9.01) | 1.02 (0.99–1.05)† | 0.22 |
| Age, yrs, mean (SD) | 42.80 (13.58) | 41.90 (12.0) | 1.01 (0.9–1.03) | 0.52 |
| Race/ethnicity (%) | ||||
| Non-Hispanic white | 64 (84) | 136 (89) | 1.0 | 0.81 |
| Hispanic | 5 (7) | 8 (5) | 1.32 (0.39–4.14) | |
| Black | 5 (7) | 8 (5) | 1.35 (0.42–4.28) | |
| Other** | 2 (2) | 2 (1) | 2.13 (0.25–18.03) | |
| Sex (%) | ||||
| Female | 52 (68) | 110 (71) | 1.0 | 0.64 |
| Male | 24 (32) | 44 (29) | 1.15 (0.65–2.15) | |
| Education (4 declined) (%) | ||||
| High school | 14 (18) | 25 (17) | 1.0 | 0.94 |
| College | 40 (53) | 82 (55) | 0.87 (0.41–1.89) | |
| Graduate | 22 (29) | 43 (28) | 0.91 (0.40–2.12) | |
| Cigarette smoking (%) | ||||
| Nonsmoker | 46 (61) | 105 (68) | 1.0 | 0.22 |
| 1–19 pack-yrs | 28 (37) | 41 (27) | 1.56 (0.86–2.82) | |
| 20+ pack-yrs | 2 (3) | 8 (5) | 0.57 (0.08–2.39) | |
| Season of blood draw | ||||
| Warm months (April–Sep) | 40 (53) | 77 (50) | 1.0 | 0.71 |
| Cold months (Oct–Mar) | 36 (47) | 77 (50) | 0.90 (0.52–1.56) | |
| Body mass index (BMI) category (6 excluded for missing data) (%) | ||||
| Normal (18.5–24.9) | 35 (47) | 65 (43) | 1.0 | 0.85 |
| Overweight (25–29.9) | 25 (19) | 55 (20) | 0.85 (0.45–1.60) | |
| Obese (30+) | 14 (34) | 30 (37) | 0.96 (0.44–2.10) | |
| Taking a supplement containing vitamin D | ||||
| Yes | 56 (74) | 101 (66) | 1.0 | 0.21 |
| No | 20 (26) | 53 (34) | 0.68 (0.36–1.24) | |
| Shared epitope (2 excluded for missing data) (%) | ||||
| No | 32 (42) | 78 (51) | 1.0 | 0.19 |
| Yes | 44 (58) | 74 (49) | 1.45 (0.83–2.54) | |
| Cohort group (%) | ||||
| HLA-DR4-enriched | 46 (61) | 94 (61) | 1.0 | 0.94 |
| First-degree relatives | 30 (39) | 60 (39) | 0.98 (0.56–1.73) | |
↵* OR calculated using univariate logistic regression;
↵** included Asian and Native American Indian;
↵† OR and 95% CI calculated based on standard deviation difference in 25,OH vitamin D level. Adjusting for age, shared epitope, and smoking status, 25,OH vitamin D levels were not associated with RA-related autoantibodies [adjusted OR 1.23 (95% CI 0.93–1.63) for a 1 standard deviation difference in 25,OH vitamin D, p = 0.15].