A multidisciplinary team from the USA analyzed the environmental factors that may be associated with primary biliary cirrhosis (PBC).
The researchers conducted a survey using standardized NHANES questions to 241 PBC patients in the United States, 261 of their siblings, and 141 friends without PBC. The overall response rate was 83 per cent among PBC cases, 67 per cent among siblings, and 63 per cent among friend controls.
The female-to-male ratio among cases in the sample was approximately 10:1; the mean age was 53 years, and 97 per cent were Caucasian.
Other autoimmune diseases reported most frequently by PBC cases included Sjogren's syndrome (17.4 per cent) and Raynaud's syndrome (12.5 per cent).
Approximately 6 per cent of cases reported at least one family member with PBC.
Odds ratios for PBC cases, compared with friends:
Other autoimmune disease 4.92
Urinary tract infection 2.12
The team found that adjusted odds ratios (OR) were elevated for cases, compared with friends, for other autoimmune diseases (OR = 4.92), smoking (OR = 2.04), tonsillectomy (OR = 1.86), and vaginal or urinary tract infection in females only (OR = 2.12). Similarly elevated ORs were observed for these risk factors when cases were compared with their siblings.
Researcher Howard Worman said, "The higher rate of urinary tract infection among cases is particularly interesting in light of previous data, and raises the possibility of an infectious etiology for PBC, and of molecular mimicry as an etiologic mechanism."
"The significance of smoking in the multivariate models supports the findings of previous studies and raises the issue of the influence of smoking on a Th1 response," he concluded.