Death rates for acquired hypothyroidism and thyrotoxicosis in English populations (1979-2010): comparison of underlying cause and all certified causes.

BACKGROUND: Overt hypothyroidism and thyrotoxicosis have widespread systemic effects and are associated with increased mortality. Most death certificates that include them do not have the thyroid disease coded as the underlying cause of death. AIM: To describe regional (1979-2010) and national (1995-2010) trends in mortality rates for acquired hypothyroidism and thyrotoxicosis, analysing all certified causes of death (termed 'mentions') and not just the underlying cause. DESIGN: Analysis of death registration data. METHODS: Analysis of data for the Oxford region (mentions available from 1979) and English national data (mentions available from 1995). The data were grouped in periods defined by different national rules for selecting the underlying cause of death (1979-83, 1984-92, 1993-2000 and 2001-10) and were also analysed as single calendar years. RESULTS: Mentions mortality for acquired hypothyroidism in the Oxford region declined significantly from 1979 to 2010: the average annual percentage change (AAPC) was -2.6% (95% confidence intervals -3.5, -1.8). Most of the decrease occurred during the 1980s. The AAPC in rates for later years in England (1995-2010) was non-significant at 0.2% (-0.7, 1.0). Mortality rates for thyrotoxicosis decreased significantly: the AAPC was -2.8% (-4.1, -1.5) in the Oxford region and -3.8% (-4.7, -3.0) in England. In England, between 2001 and 2010, hypothyroidism or thyrotoxicosis was coded as the underlying cause of death on, respectively, 17 and 24% of death certificates that included them. CONCLUSION: Mortality rates for hypothyroidism and thyrotoxicosis have fallen substantially. The fall is probably wholly or mainly a result of improved care.