Table 1.

Baseline characteristics of individuals with and without incident ankylosing spondylitis (AS).

Control Group, n = 35,278Incident AS, n = 107p valuei
Ageii (years)46.7 (46.6–46.8)40.8 (38.5–43.1)< 0.001
Males/females15,905 (45.1%)/19,373 (54.9%)44 (41.1%)/63 (58.9%)0.41
Body mass indexiii (kg/m2)25.7 (25.7–25.7)25.7 (25.2–26.4)0.58
Hypertension12,807 (36.3%)44 (41.1%)0.31
Diabetes507 (1.4%)2 (1.9%)0.71
Previous CVD1,242 (3.5%)4 (3.7%)0.91
Smoking HUNT2< 0.01
  Never smoker15,784 (44.7%)38 (35.5%)
  Former smoker8,395 (23.8%)19 (17.8%)
  Present smoker9,223 (26.1%)41 (38.3%)
Pack-years HUNT2 (former and present smokers)iii9.6 (9.5–10.0)7.7 (5.3–10.3)0.12
Change in smoking habits, HUNT2 to HUNT30.08
  Never smoker13,698 (38.8%)34 (31.8%)
  Quit smoking10,812 (30.6%)33 (30.8%)
  Started smoking or continuous smoker6,434 (18.2%)28 (26.2%)
HLA-B27 genotypesiv< 0.001
  HLA-B27–positive112 (12.1%)50 (48.5%)
  HLA-B27–negative812 (87.9%)53 (51.5%)

  • ↵i t test, Mann-Whitney U test, or chi-square test.

  • ↵ii Data are given as mean or

  • ↵iii median (95% CI) or frequency (%).

  • ↵iv Data available for 924 controls and 103 incident AS cases. CVD: cardiovascular disease.