Table 1.
Descriptive characteristics of 960 incident cases of primary Sjögren's syndrome and 9035 matched controls from the general population
| Primary Sjögren's syndrome patients | General population controls | ||
|---|---|---|---|
| Size, n (% females) | All patients | 960 (93%) | 9035 (93%) |
| SSA/SSB double‐positive | 391 (90%) | 3700 (90%) | |
| SSA/SSB single‐positive | 278 (92%) | 2595 (93%) | |
| SSA/SSB‐negative | 274 (96%) | 2583 (96%) | |
| Age in years at primary Sjögren's syndrome diagnosis, mean (SD) | All patients | 55.4 (15) | – |
| SSA/SSB double‐positive | 51.8* (15) | – | |
| SSA/SSB single‐positive | 56.6** (14) | – | |
| SSA/SSB‐negative | 59.1 (13) | – | |
| Years of follow‐up time after primary Sjögren's syndrome diagnosis date, median (IQR) | All patients | 9.5 (4.5–14.6) | 9.5 (4.5–15.5) |
| SSA/SSB double‐positive | 9.5 (4.5–15.5) | 10.5 (4.6–16.5) | |
| SSA/SSB single‐positive | 8.9 (4.5–13.5) | 9.5 (4.5–14.5) | |
| SSA/SSB‐negative | 8.5 (3.5–14.9) | 9.3 (3.5–15.5) |
Seventeen primary Sjögren's syndrome patients did not have available records on Ro/SSA and La/SSB antibodies, and are hence not included in subgroup analyses.
IQR, interquartile range; SD, standard deviation; SSA, Ro/SSA antibodies; SSB, La/SSB antibodies.
Two‐sided t‐test for means difference: *P < 0.0001 compared to SSA/SSB single‐positive, P < 0.0001 compared to SSA/SSB‐negative, **P = 0.024 compared to SSA/SSB‐negative.