GJ Webb et al. Clin Gastroenterol Hepatol 2021; 19: 2587-2596. Open Access: The Epidemiology of UK Autoimmune Liver Disease Varies With Geographic Latitude
Methods: A retrospective cohort study using anonymized UK primary care records (2002-2016). All adults without a baseline diagnosis of AILD (autoimmune liver disease) were included and followed up until the first occurrence of an AILD diagnosis, death, or they left the database.
AIH, autoimmune hepatitis; PBC, primary biliary cholangitis; PSC, primary sclerosing cholangitis
- 1314 incident cases of PBC, 396 of PSC, and 1034 of AIH. Crude incidences were as follows: PBC, 2.47 (95% CI, 2.34–2.60); PSC, 0.74 (95% CI, 0.67–0.82); and AIH, 1.94 (95% CI, 1.83–2.06) per 100,000 per year.
- A more northerly latitude was associated strongly with incidence of PBC: 2.16 to 4.86 from 50°N to 57°N (P = .002) and incidence of AIH: 2.00 to 3.28 (P = .003), but not incidence of PSC: 0.82 to 1.02 (P = .473)
- After adjustments, PBC was more frequent in smokers than those who had never smoked at 3.40 (3.03–3.77) per 100,000/y and 1.96 (1.80–2.12) cases per 100,000/y; there was a lower incidence of PSC in smokers 0.47 (0.33–0.61) per 100,000/y compared with those who had never smoked 0.95 (0.83–1.07) per 100,000/y. For AIH, there was no difference between current smokers and those who had never smoked
The authors speculate in the discussion about potential reasons why latitude could correlate with disease incidence. Some potential explanations include sunlight/vitamin D metabolism (though this is at odds with the fact that those with increased skin pigmentation are NOT at increased risk), environmental exposures (related to geology, diet, air quality) or unrecognized genetic tendency based on geography.
My take: In the UK, there is an association between a more northernly latitude and both PBC and AIH.
Related blog post: Aspen Webinar 2021 Part 5 -Autoimmune Liver Disease & PSC