Seasonal variation in the diagnosis of primary biliary cirrhosis: further evidence for an environmental component to etiology

  1. Lookup NU author(s)
  2. Dr Richard McNally
  3. Dr Peter James
  4. Sam Ducker
  5. Emeritus Professor Oliver James
Author(s)McNally RJQ, James PW, Ducker S, James OFW
Publication type Article
JournalHepatology
Year2011
Volume54
Issue6
Pages2099-2103
ISSN (print)0270-9139
ISSN (electronic)1527-3350
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The etiology of primary biliary cirrhosis (PBC) is far from clear. Both genetic and environmental factors are likely to be involved. We have previously reported evidence of space-time clustering suggesting that a transient environmental agent may be involved in etiology. To further examine whether a seasonally varying environmental agent may contribute to the etiology of PBC we have analyzed seasonal variation with respect to month of diagnosis using population-based data from northeast England over a defined period (1987–2003). Date of diagnosis was defined as the earliest date at which the patient was found to have fulfilled any two of three diagnostic criteria (AMA positive titre ≥ 1 in 40, cholestatic liver blood tests, diagnostic or compatible liver histology). Monthly expected (E) numbers of cases were calculated under an assumption of a uniform distribution throughout the year. Observed counts (O) were compared with the expected numbers. The chi-squared heterogeneity test was used to test for overall non-uniform variation and also for individual months. Poisson regression analysis was used to fit a sinusoidal (harmonic) model to the data, using month of diagnosis as a covariate in the model. There was a marked peak for diagnoses in the month of June (O = 115, E = 84.7, O/E = 1.36, P = 0.001). Furthermore, there was evidence of a sinusoidal pattern with a June peak (P = 0.012). In conclusion, these highly novel results provide further evidence for the involvement of a seasonally varying environmental agent in the etiology of PBC.
PublisherJohn Wiley & Sons, Inc.
URLhttp://dx.doi.org/10.1002/hep.24597
DOI10.1002/hep.24597
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