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Table 1 Baseline age-standardized characteristics of participants in the Nurses’ Health Study in 1984 and Nurses’ Health Study II in 1991 categorized by total fish intake (n = 166,013)

From: Association of fish intake and smoking with risk of rheumatoid arthritis and age of onset: a prospective cohort study

Characteristics Total fish servings
NHS (n = 76,540) NHSII (n = 89,473)
None to < 1/month 1/month to < 1/week 1 to < 2.5/week 2.5 to < 4/week ≥4/week None to < 1/month 1/month to < 1/week 1 to < 2.5/week 2.5 to < 4/week ≥4/week
Participants, n (%) 4343 (5.7) 10,165 (13.3) 40,913 (53.5) 7284 (9.5) 13,835 (18.1) 8296 (9.3) 15,470 (17.3) 46,496 (52.0) 6933 (7.7) 12,278 (13.7)
Age in years, mean (SD)a 50.8 (7.3) 50.1 (7.3) 50.1 (7.2) 51.1 (7.0) 50.8 (7.0) 35.6 (4.8) 35.9 (4.7) 36.1 (4.6) 36.4 (4.5) 36.4 (4.6)
Calorie intake/day (SD) 1554 (526) 1605 (514) 1737 (514) 1835 (537) 1868 (543) 1593 (532) 1640 (521) 1791 (527) 1914 (544) 2025 (556)
White race, % 97.3 97.3 97.6 96.0 96.8 93.1 93.4 93.5 91.2 90.1
Median household income quartile, %b
 Q1 – lowest income 30.7 28.2 24.5 22.1 21.1 25.9 25.6 24.4 21.4 22.8
 Q2 26.9 25.6 25.7 23.0 23.2 26.7 26.2 25.1 22.4 23.0
 Q3 22.3 24.4 25.0 25.3 27.3 25.3 25.6 25.3 24.6 25.2
 Q4 – highest income 20.1 21.7 24.8 29.6 28.4 22.2 22.7 25.2 31.7 29.0
Smoked > 10 pack years, % 36.6 37.0 36.2 36.0 36.8 16.1 15.5 15.8 16.2 16.8
Ever smoked, % 53.2 54.4 55.8 57.8 59.5 32.8 32.7 34.4 37.8 36.8
Smoking status/intensity, %
 Never 46.8 45.6 44.2 42.2 40.5 67.2 67.3 65.6 62.2 63.2
 Past, 1–14 cigarettes/day 12.3 13.6 15.8 17.1 18.6 10.7 11.1 12.6 14.7 13.9
 Past, ≥15 cigarettes/day 13.5 14.3 15.4 17.4 20.0 9.6 9.3 9.7 10.8 11.1
 Current, 1–14 cigarettes/day 7.2 7.4 7.3 8.1 7.9 5.0 5.1 5.5 6.0 5.8
 Current, ≥15 cigarettes/day 20.2 19.1 17.2 15.2 13.0 7.5 7.2 6.5 6.3 6.0
Parity/breastfeeding duration, %
 Nulliparous 7.0 6.0 5.4 6.6 6.0 30.5 25.5 24.5 29.4 30.8
 Parous/none to < 1 month 45.2 43.6 42.7 40.3 41.6 14.8 14.8 13.2 11.5 11.6
 Parous/1 to < 12 months 28.7 31.0 30.8 31.3 31.1 22.6 24.7 25.0 23.5 23.0
 Parous/≥12 months 14.7 14.8 16.9 17.1 16.6 24.0 27.3 29.9 28.0 26.5
Menopausal status/postmenopausal hormone use
 Premenopausal 39.0 40.1 40.8 40.1 39.5 91.6 91.9 92.6 92.8 92.3
 Postmenopausal/never use 31.7 31.4 31.5 31.6 31.8 3.8 3.8 3.4 3.3 3.4
 Postmenopausal/ever use 26.4 25.8 25.4 26.0 26.5 4.3 4.1 3.8 3.6 4.1
Body mass index category, %
 Underweight/normal (< 25 kg/m2) 64.1 63.3 61.8 60.7 54.1 68.2 68.1 67.6 67.7 63.3
 Overweight (25 to < 30 kg/m2) 23.6 24.5 25.7 26.2 30.5 18.7 18.7 19.9 20.0 22.2
 Obese (≥30 kg/m2) 12.3 12.2 12.5 13.1 15.3 13.1 13.1 12.5 12.2 14.5
Alcohol intake, %
 None to < 5 g/day 73.9 70.2 63.8 58.5 63.0 84.5 82.8 79.6 74.7 77.5
 5 to < 10 g/day 8.6 9.2 12.1 12.6 12.5 8.5 9.3 10.9 14.0 11.3
 ≥ 10 g/day 17.5 20.5 24.1 28.9 24.5 7.0 7.9 9.5 11.3 11.2
  1. Missing values are not shown
  2. a Value is not age-standardized
  3. b Median household income was obtained from US Census-tract data in 1986 for the NHS