Table 2 Multivariate Cox proportional regression analysis for seropositive rheumatoid arthritis occurrence.

Age (years, N)

Age (30–39, N = 68,667)

(reference)

Age (40–49, N = 140,709)

1.676

1.303–2.156

Age (50–59, N = 139,100)

2.445

1.909–3.131

Age (60–69, N = 91,699)

2.444

1.884–3.170

Age (70–79, N = 56,800)

2.063

1.563–2.772

Age (≥ 80, N = 20,071)

1.320

0.944–1.846

Sex

Female (N = 255,242)

(reference)

Male (N = 251,954)

0.387

0.340–0.441

Annual income

70–100th percentile (Low, N = 227,484)

(reference)

40–70th percentile (N = 143,897)

0.995

0.888–1.116

 > 40th percentile (High, N = 145,368)

1.045

0.937–1.164

Residence

Rural (N = 279,404)

(reference)

City (N = 231,738)

0.871

0.794–0.956

CCI (N = 517,053)

1.341

1.327–1.354

Smoking behaviour

Current non-smoker (N = 391,405)

(reference)

Current smoker (N = 125,648)

0.934

0.789–1.106

Alcohol consumption

Alcohol non-drinker (N = 287,068)

(reference)

Alcohol mild drinker (1–4 cups per week, N = 62,381)

0.881

0.750–1.036

Alcohol moderate drinker (5–10 cups per week, N = 51,118)

0.810

0.657–0.999

Alcohol heavy drinker (over 10 cups per week, N = 116,485)

0.914

0.771–1.083

Regular exercise levels

Non-regular exercise (N = 132,519)

(reference)

Mild regular exercise (N = 132,751)

1.006

0.892–1.134

Moderate regular exercise (N = 66,627)

1.060

0.916–1.226

High regular exercise (N = 185,156)

0.834

0.737–0.944

BMI category (kg/m²)

Underweight (BMI < 18.5, N = 17,835)

1.225

0.969–1.550

Normal (BMI 18.5–22.9, N = 196,406)

(reference)

Pre-obese (BMI 23–24.9, N = 126,291)

0.780

0.692–0.880

Obese class I (BMI 25–29.9, N = 155,338)

0.774

0.690–0.869

Obese class II (BMI 30–34.9, N = 19,130)

0.583

0.440–0.772

Obese class III (BMI ≥ 35, N = 2,053)

0.837

0.431–1.625

Diabetes mellitus (N = 517,053)

0.959

0.858–1.071

Hypertension (N = 517,053)

1.108

0.988–1.242

Hyperlipidemia (N = 517,053)

1.226

1.104–1.362