Table 6

Non-genetic factors and risk of anti-CCP-positive and anti-CCP-negative rheumatoid arthritis, Denmark 1998 to 2003

Anti-CCP-positive rheumatoid arthritis
 Anti-CCP-negative rheumatoid arthritis
 Test for homogeneity anti-CCP-positive versus anti-CCP-negative rheumatoid arthritis (p)



Number of patients/controls
 ORa (95% CI)
 ORb (95% CI)
 Number of patients/controls
 ORa (95% CI)
 ORb (95% CI)
Age at menarche (women only)






     ≤12 years
 48/145
 1 (ref)
 1 (ref)
 27/145
 1 (ref)
 1 (ref)
     13 years
 52/130
 1.24 (0.77 to 1.99)
 1.33 (0.79 to 2.26)
 22/130
 0.88 (0.47 to 1.66)
 1.06 (0.52 to 2.14)
     14 years
 46/105
 1.35 (0.82 to 2.22)
 1.54 (0.88 to 2.69)
 26/105
 1.24 (0.67 to 2.29)
 1.86 (0.93 to 3.70)
 0.68
     ≥15 years
 52/80
 1.91 (1.16 to 3.16)
 2.07 (1.18 to 3.63)
 27/80
 1.75 (0.93 to 3.29)
 2.27 (1.13 to 4.57)
     Trend test (p)
0.01
 0.01
0.06
 0.01








Oral contraceptive pills (women only)






     Never
 64/165
 1 (ref)
 1 (ref)
 33/165
 1 (ref)
 1 (ref)
     Ever
 145/312
 1.37 (0.93 to 2.02)
 1.65 (1.06 to 2.57)
 70/312
 1.20 (0.73 to 1.98)
 1.19 (0.68 to 2.07)
 0.34
     Test for homogeneity (p)
0.11
 0.03
0.48
 0.53








Marital status






     Married or cohabiting with partner
 227/581
 1 (ref)
 1 (ref)
 106/581
 1 (ref)
 1 (ref)
     Widowed
 8/24
 0.79 (0.33 to 1.89)
 0.50 (0.19 to 1.34)
 5/24
 0.86 (0.30 to 2.47)
 0.72 (0.23 to 2.24)
     Divorced or separated
 30/99
 0.76 (0.48 to 1.19)
 0.62 (0.36 to 1.04)
 11/99
 0.58 (0.29 to 1.13)
 0.48 (0.22 to 1.06)
 0.77
     Unmarried
 44/65
 1.98 (1.25 to 3.14)
 1.65 (0.96 to 2.84)
 14/65
 1.47 (0.75 to 2.92)
 1.19 (0.53 to 2.67)
     Test for homogeneity (p)
0.01
 0.03
0.24
 0.28








Smoker status






     Never
 84/298
 1 (ref)
 1 (ref)
 51/298
 1 (ref)
 1 (ref)
     Former
 60/155
 1.53 (1.02 to 2.29)
 1.57 (0.99 to 2.48)
 33/155
 1.41 (0.84 to 2.34)
 1.35 (0.76 to 2.39)
 0.03
     Current
 165/316
 2.13 (1.54 to 2.95)
 1.73 (1.17 to 2.56)
 52/316
 1.01 (0.65 to 1.57)
 0.83 (0.49 to 1.39)
     Test for homogeneity (p)
<0.001
 0.02
0.35
 0.22








Pack-years smokedc






     0 pack-years
 84/298
 1 (ref)
 1 (ref)
 51/298
 1 (ref)
 1 (ref)
     >0 to 10 pack-years
 51/142
 1.32 (0.86 to 2.01)
 1.31 (0.81 to 2.12)
 27/142
 1.22 (0.71 to 2.08)
 1.20 (0.66 to 2.17)
     >10 to 20 pack-years
 73/125
 2.47 (1.65 to 3.69)
 2.41 (1.51 to 3.82)
 19/125
 0.84 (0.46 to 1.52)
 0.72 (0.37 to 1.40)
 0.08
     >20 pack-years
 100/196
 2.25 (1.53 to 3.32)
 1.65 (1.03 to 2.64)
 37/196
 1.31 (0.78 to 2.19)
 1.00 (0.54 to 1.88)
     Trend test (p)
<0.001
 0.03
0.47
 0.76








Coffee consumptiond






     0 cups per day
 44/142
 1 (ref)
 1 (ref)
 25/142
 1 (ref)
 1 (ref)
     >0 to 5 cups per day
 110/326
 1.20 (0.76 to 1.91)
 1.33 (0.77 to 2.30)
 53/326
 0.84 (0.47 to 1.53)
 0.79 (0.41 to 1.52)
     >5 to 10 cups per day
 112/234
 1.83 (1.12 to 2.97)
 1.70 (0.95 to 3.05)
 45/234
 1.07 (0.57 to 2.00)
 0.94 (0.47 to 1.90)
 0.46
     >10 cups per day
 43/65
 2.75 (1.52 to 4.99)
 2.18 (1.07 to 4.42)
 13/65
 1.38 (0.61 to 3.15)
 1.23 (0.48 to 3.16)
     Trend test (p)
<0.001
 0.02
0.22
 0.44








Alcohol consumptiond,e






     0 drinks per week
 58/93
 1.68 (1.10 to 2.55)
 1.98 (1.22 to 3.19)
 18/93
 0.88 (0.48 to 1.64)
 0.72 (0.34 to 1.48)
     >0 to 5 drinks per week
 124/302
 1 (ref)
 1 (ref)
 60/302
 1 (ref)
 1 (ref)
     >5 to 10 drinks per week
 63/163
 0.96 (0.66 to 1.39)
 1.10 (0.73 to 1.66)
 27/163
 0.89 (0.53 to 1.48)
 1.01 (0.58 to 1.74)
 0.01
     >10 to 15 drinks per week
 26/75
 0.82 (0.49 to 1.38)
 0.98 (0.55 to 1.76)
 9/75
 0.67 (0.31 to 1.45)
 0.78 (0.33 to 1.84)
     >15 drinks per week
 32/130
 0.58 (0.35 to 0.94)
 0.60 (0.35 to 1.04)
 21/130
 1.36 (0.73 to 2.52)
 1.36 (0.68 to 2.74)
     Trend test (p)
0.002
 0.01
0.45
 0.34








Wine consumptiond






     0 glasses per week
 96/200
 1.18 (0.86 to 1.63)
 1.18 (0.82 to 1.71)
 36/200
 0.98 (0.62 to 1.55)
 0.86 (0.51 to 1.45)
     >0 to 5 glasses per week
 168/390
 1 (ref)
 1 (ref)
 72/390
 1 (ref)
 1 (ref)
     >5 to 10 glasses per week
 30/124
 0.52 (0.33 to 0.81)
 0.59 (0.36 to 0.98)
 17/124
 0.77 (0.43 to 1.38)
 0.76 (0.39 to 1.45)
 0.03
     >10 to 15 glasses per week
 7/33
 0.46 (0.20 to 1.09)
 0.45 (0.17 to 1.21)
 6/33
 0.99 (0.38 to 2.56)
 0.83 (0.27 to 2.61)
     >15 glasses per week
 5/19
 0.66 (0.24 to 1.84)
 0.90 (0.29 to 2.76)
 5/19
 1.59 (0.54 to 4.66)
 2.29 (0.71 to 7.42)
     Trend test (p)
0.003
 0.04
0.77
 0.46








Body mass indexd






     <18.5 kg/m2 (underweight)
 19/41
 1.22 (0.65 to 2.29)
 0.88 (0.43–1.80)
 4/41
 0.34 (0.10 to 1.19)
 0.35 (0.09 to 1.34)
     18.5 to <25 kg/m2 (normal weight)
 184/464
 1 (ref)
 1 (ref)
 77/464
 1 (ref)
 1 (ref)
     25 to <30 kg/m2 (overweight)
 77/196
 1.04 (0.74 to 1.45)
 1.01 (0.69 to 1.47)
 35/196
 1.20 (0.75 to 1.93)
 1.24 (0.74 to 2.10)
 0.004
     ≥30 kg/m2 (obese)
 25/51
 1.34 (0.79 to 2.28)
 1.15 (0.62 to 2.13)
 20/51
 3.22 (1.73 to 5.98)
 3.45 (1.73 to 6.87)
     Trend test (p)
0.53
 0.63
<0.001
 <0.001








Physical activity at workd






     Not physically demanding
 34/153
 1 (ref)
 1 (ref)
 23/153
 1 (ref)
 1 (ref)
     Slightly physically demanding
 63/177
 1.60 (0.99 to 2.58)
 1.10 (0.65 to 1.87)
 39/177
 1.51 (0.85 to 2.69)
 1.41 (0.74 to 2.67)
     Moderately physically demanding
 93/191
 2.24 (1.41 to 3.54)
 1.64 (0.98 to 2.73)
 30/191
 1.08 (0.59 to 1.97)
 1.02 (0.52 to 1.99)
 0.84
     Very physically demanding
 70/152
 2.03 (1.26 to 3.27)
 1.18 (0.68 to 2.06)
 34/152
 1.53 (0.84 to 2.77)
 1.33 (0.66 to 2.67)
     Unemployed
 48/96
 2.58 (1.45 to 4.61)
 1.95 (1.00 to 3.81)
 10/96
 0.47 (0.18 to 1.23)
 0.41 (0.13 to 1.23)
     Trend test (p)f,g
0.002
 0.30
0.34
 0.57








Physical activity in leisure timed






     Not physically demanding
 35/57
 1 (ref)
 1 (ref)
 11/57
 1 (ref)
 1 (ref)
     Slightly physically demanding
 108/226
 0.74 (0.45 to 1.21)
 0.97 (0.56 to 1.70)
 49/226
 0.95 (0.45 to 1.98)
 0.87 (0.39 to 1.94)
     Moderately physically demanding
 137/405
 0.51 (0.32 to 0.83)
 0.76 (0.43 to 1.32)
 66/405
 0.69 (0.33 to 1.42)
 0.76 (0.34 to 1.67)
 0.75
     Very physically demanding
 29/80
 0.60 (0.32 to 1.13)
 0.90 (0.44 to 1.86)
 10/80
 0.60 (0.23 to 1.59)
 0.59 (0.20 to 1.70)
     Trend test (p)f
0.008
 0.32
0.10
 0.29








Pets as adult






     Never
 52/87
 1 (ref)
 1 (ref)
 20/87
 1 (ref)
 1 (ref)
     Ever
 257/682
 0.59 (0.40 to 0.87)
 0.62 (0.39 to 0.99)
 116/682
 0.65 (0.37 to 1.14)
 0.61 (0.33 to 1.16)
 0.98
     Test for homogeneity (p)
0.01
 0.04
0.13
 0.13








Asthmah






     Never
 288/699
 1 (ref)
 1 (ref)
 131/699
 1 (ref)
 1 (ref)
     Ever
 21/68
 0.73 (0.43 to 1.23)
 0.58 (0.32 to 1.08)
 4/68
 0.32 (0.11 to 0.91)
 0.28 (0.09 to 0.85)
 0.23
     Test for homogeneity (p)
0.23
 0.09
0.03
 0.02








Schizophrenia among first-degree relatives






     No
 299/758
 1 (ref)
 1 (ref)
 134/758
 1 (ref)
 1 (ref)
     Yes
 10/11
 3.36 (1.32 to 8.51)
 4.18 (1.54 to 11.3)
 2/11
 1.16 (0.24 to 5.55)
 0.51 (0.06 to 4.44)
 0.16
     Test for homogeneity (p)
0.01
 0.005
0.85
 0.54

Due to missing values for some individuals, numbers do not always add up to 309 anti-CCP-positive and 136 anti-CCP-negative patients with RA and 769 controls. aAdjusted for gender, birth year, and year or pseudo-year of RA diagnosis. bAdjusted for gender, birth year, year or pseudo-year of RA diagnosis, place of residence, educational status, history of urinary tract infection, and all other variables in the table. Smoking variables not adjusted for the other measure of smoking, and alcohol and wine variables not adjusted for each other. cOne pack-year is equivalent to 7,300 cigarettes (20 cigarettes per day for 1 year). dTen years prior to interview. eOne drink is equivalent to one bottle of normal beer, 0.67 bottle of strong beer, or one glass of wine, dessert wine, or spirits. fTrend tests based on original categories enumerated by consecutive numbers starting with one. gIncluding only individuals who were employed. hPhysician-verified diagnosis before age 45 years. CI, confidence interval; OR, odds ratio; ref, reference.

Pedersen et al. Arthritis Research & Therapy 2006 8:R133   doi:10.1186/ar2022