Characteristics | NHS (388 matched pairs) | NHSII (49 matched pairs) | ||
---|---|---|---|---|
 | RA cases | Controls | RA cases | Controls |
Matching factors | Â | Â | Â | Â |
   Age (years; mean ± SD) | 57 ± 9 | 57 ± 9 | 43 ± 5 | 43 ± 5 |
   Postmenopausal (n [%]) | 263 (68%) | 255 (66%) | 14 (29%) | 14 (29%) |
   Current PMH use (n [%])a | 111 (36%) | 101 (34%) | 11 (69%) | 12 (75%) |
Other characteristics | Â | Â | Â | Â |
   Ever cigarette smokers (n [%]) | 246 (63%) | 220 (57%) | 19 (39%) | 22 (45%) |
   Pack-years among smokers, mean (SD) | 24 ± 17 | 24 ± 20 | 16 ± 9 | 11 ± 6 |
   Parous (n [%]) | 352 (91%) | 367 (95%) | 46 (94%) | 42 (86%) |
   Breastfed babies ≥ 12 months total, among parous (n [%])a | 44 (13%) | 65 (18%) | 18 (43%) | 18 (45%) |
   Age at menarche <12 years (n [%]) | 87 (22%) | 77 (20%) | 16 (33%) | 15 (31%) |
   Irregular menstrual cycle (n [%]) | 55 (14%) | 49 (13%) | 9 (18%) | 11 (22%) |
   Husband education > college graduate (n [%]) | 77 (20%) | 77 (20%) | 19 (39%) | 9 (18%) |
   Physical activity (hours/day mean ± SD) | 2 ± 3 | 2 ± 5 | 2 ± 3 | 3 ± 3 |
   Alcohol intake (g/day; mean ± SD) | 6 ± 10 | 6 ± 9 | 2 ± 1 | 2 ± 2 |
   Body mass index (kg/m2; mean ± SD) | 25 ± 4 | 26 ± 5 | 27 ± 7 | 26 ± 5 |