Outcomes

The primary outcome was the occurrence of autoimmune diseases. Several autoimmune diseases were defined as catastrophic illnesses in the NHI and that certification requires precise fulfillment of related classification criteria as follows: American College of Rheumatology (ACR) 1997 revised criteria for systemic lupus erythematosus (SLE, ICD-9-CM: 710.0)¹⁶; American Rheumatism Association 1987 revised criteria for rheumatoid arthritis (RA, ICD-9-CM: 714.0)¹⁷; ACR criteria for systemic sclerosis (SSc, ICD-9-CM: 710.1)¹⁸; American-European Consensus Group 2002 revised criteria for Sjogren's syndrome (ICD-9-CM: 710.2)¹⁹; Bohan and Peter 1975 criteria for polymyositis and dermatomyositis (ICD-9-CM: 710.3)^20,21; International Study Group 1990 criteria for Behçet disease (ICD-9-CM: 136.1)²²; and ACR 1990 criteria for temporal arteritis (ICD-9-CM: 443.1),²³ granulomatosis polyangiitis (GPA, ICD-9-CM: 446.4),²⁴ and Takayasu arteritis (ICD-9-CM: 446.7).²⁵ After strict verification by a review committee, patients are enrolled in the registry of catastrophic illnesses. The main end point was development of autoimmune diseases, defined by catastrophic illness certification of these diseases. All cases were followed until the development of autoimmune diseases, death, withdrawal from the insurance program, or the end of the study period in 2012. Incidence rates (per 100,000 person-years) and incidence rate ratios were analyzed. The brief summary of the classification criteria of major autoimmune diseases was shown in Table 1.

Brief summary of classification of major systemic autoimmune diseases.

We also investigated the effects of OSA treatment on the risk of developing autoimmune diseases. The patients with OSA were divided into two groups, those with and without OSA treatment. Treatment included surgery (pharyngeal or nasal surgery) and continuous positive airway pressure (CPAP). The types of pharyngeal surgery included were tonsillectomy, adenoidectomy, adenotonsillectomy, and uvulopalatopharyngoplasty. The nasal surgeries included septoplasty, turbinoplasty, stomatoplasty, and laser turbinoplasty.