Update on the epidemiology of primary biliary cirrhosis.

The epidemiology of primary biliary cirrhosis was described as early as the 1970s, yet decades later the true frequency of this disease and its associated risk factors are still in question. There has been a wealth of data documenting the various incidence and prevalence rates across the world, demonstrating potential risk factors inherent to geographic differences. Studies that follow primary biliary cirrhosis in a set population over time have offered the most reliable picture of disease frequency. Analysis of clustering effects through region and time has offered valuable information on the complexity of the disease development. Improved epidemiologic surveillance of primary biliary cirrhosis around the world will be necessary to provide definitive evidence on the phenomenon of clustering and its associations with proposed risk factors in the literature.