Multivariable models for assessing the slope of disability over time, adjusting for the influence of age, gender, non-white ethnicity, baseline disease duration, body mass index and smoking status†
| Model/covariate | Observations in the model (n) | β Coefficient (slope of the time–trend line) | 95% CI |
|---|---|---|---|
| Overall, annually | 53 019 | −0.0170 | −0.018 to −0.015 |
| Subgroups | |||
| Age <65 years | 29 591 | −0.0160 | −0.018 to −0.014 |
| Age ≥65 years | 23 428 | −0.0199 | −0.022 to −0.018 |
| Men only | 11 158 | −0.0270 | −0.031 to −0.024 |
| Women only | 41 861 | −0.0140 | −0.016 to −0.012 |
| Caucasians only | 48 481 | −0.0170 | −0.019 to −0.016 |
| All non-Caucasians | 4538 | −0.0170 | −0.019 to −0.010 |
| African–Americans | 1068 | −0.0110 | −0.02 to 0.007 |
| Non-smokers only | 43 473 | −0.0190 | −0.02 to −0.017 |
| Smokers only | 9696 | −0.0080 | −0.012 to −0.004 |
| Baseline disease duration <3 years | 9696 | −0.0080 | −0.011 to −0.004 |
| Body mass index ≥30 | 9953 | −0.0210 | −0.024 to −0.018 |
| Body mass index <30 | 43 066 | −0.0160 | −0.017 to −0.014 |
↵† Our primary outcome (dependent variable) was the trend (slope) of the HAQ-DI score over time. In multivariable regression models, our adjustments included gender, ethnicity and baseline measures of age, disease duration and smoking. We also took into account the patient's calendar year of entry into the ARAMIS cohort to allow for the possibility of bias due to time trends in recruitment.
ARAMIS, Arthritis, Rheumatism and Aging Medical Information System; DMARD, disease-modifying anti-rheumatic drug; HAQ-DI, Health Assessment Questionnaire Disability Index.