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Incidence and mortality of bullous pemphigoid and pemphigus vulgaris in the UK

Incidence and mortality of bullous pemphigoid and pemphigus vulgaris in the UK. Sin éad Langan Joe West. Bullous pemphigoid. Incidence rates between 0.2 and 3 per 100,000 person-years Estimated incidence of 1.4 per 100,000 person-years in Scotland Reported 1-year mortality rates

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Incidence and mortality of bullous pemphigoid and pemphigus vulgaris in the UK

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  1. Incidence and mortality of bullous pemphigoid and pemphigus vulgaris in the UK Sinéad Langan Joe West

  2. Bullous pemphigoid Incidence rates between 0.2 and 3 per 100,000 person-years Estimated incidence of 1.4 per 100,000 person-years in Scotland Reported 1-year mortality rates between 6% (USA) and 41% (France)

  3. Pemphigus vulgaris Few studies, incidence between 0.08 and 1.6 per 100,000 person-years No data from the UK 1 year mortality rates between 4.8 and 54%; no clear estimate of overall disease- specific mortality rates

  4. Objectives To determine incidence and mortality of bullous pemphigoid and pemphigus vulgaris in the United Kingdom (UK)

  5. Data source Computerised medical records from the Health Improvement Network (THIN), a large population-based UK general practice database were analysed

  6. Confounders • Age group in 10 year bands • Gender • Region • Townsend scores

  7. Study populations • All patients >20 years with bullous pemphigoid and pemphigus vulgaris diagnosed 1996-2006 • First 3 months following registration excluded • 4 matched controls selected per case

  8. Incidence • Incidence rates by age category, gender and calendar period • Incidence rate ratios (IRR) adjusting for changes in age, gender structure and calendar period over time

  9. Mortality • Deaths in cases and controls • Kaplan-Meier techniques used to calculate 1 year mortality and 5 year survival rates • Cox regression to compare mortality experience of cases and controls

  10. ONS data Incidence and mortality rates from this study applied to ONS population data to calculate expected numbers of new cases and number of deaths

  11. Results

  12. Age at diagnosis

  13. Bullous pemphigoid • 868 people with bullous pemphigoid and 3453 matched controls • Median (IQR) age at first presentation for bullous pemphigoid 80 (15) years • 534 (61%) were female

  14. Pemphigus vulgaris • 139 people with pemphigus vulgaris and 551 matched controls • Median (IQR) age at first presentation for pemphigus vulgaris 71 (30) years • 91 (66%) were female

  15. Incidence rates

  16. Bullous pemphigoid incidence • Crude incidence= 4.3 (95% CI 4.0-4.6) per 100,000 py • 17% increase per year (IRR 1.2, 95% CI 1.1-1.2), adjusted for gender and age • No association with region or Townsend scores

  17. Survival rates

  18. Bullous pemphigoid mortality 1-year mortality rate=19% (95% CI 16-22) Absolute excess mortality for cases=70 deaths per 1000py Hazard ratios: Crude 2.1 (95% CI 1.8-2.4) Adjusted 2.3 (95% CI 2.0-2.7)

  19. Incidence rates

  20. Pemphigus vulgarisincidence • Crude incidence= 0.7 (95% CI 0.6-0.8) per 100,000 py • 11% increase per year (IRR 1.1, 95% CI 1.0-1.2), adjusted for gender and age • No association with region or Townsend scores

  21. Survival rates

  22. Pemphigus vulgarismortality 1-year mortality rate=12% (95% CI 8-19) Absolute excess mortality for cases=62 deaths per 1000py Hazard ratios: Crude 2.8 (95% CI 1.9-4.3) Adjusted 3.4 (95% CI 2.2-5.2)

  23. Mortality rates

  24. Incidence over time

  25. Deaths over time

  26. How many new cases per year? Bullous pemphigoid Applied to ONS data, 2370 new cases per year Pemphigus vulgaris Applied to ONS data, 467 new Cases per year

  27. How many deaths between 2001 and 2005? Bullous pemphigoid Estimated 1977 deaths over 5 years (vs. 190, ONS) Pemphigus vulgaris Estimated 221 deaths over 5 years (vs. 36, ONS)

  28. Key findings • Increased incidence both diseases between 1996 and 2006 • No reduction in mortality rates • Therefore unlikely to be due to ascertainment

  29. Strengths • Large population-based study • Less susceptible to selection bias • Power • Diagnoses usually made with skin biopsy in secondary care • Previous studies confirm validity of diagnoses in THIN • Limited to “up to standard” data

  30. Limitations • Routine data • Cannot comment on disease severity • Possible misclassification of prevalent cases; possible underestimation of mortality rates

  31. Comparison to other research

  32. Conclusion • Increasing incidence rates over time • No variation by region or socioeconomic status • Mortality rates twice (pemphigoid) and three times (pemphigus) higher than matched controls

  33. Implications • Increasing population age, likely increase in morbidity and mortality from these diseases • Other measures of disease occurrence underestimate associated mortality

  34. Acknowledgements Dr Chris Smith, Professor Liam Smeeth, Dr Kate Fleming and Professor Richard Hubbard Professor Hywel Williams for guidance and support

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