Epidemiology of hereditary transthyretin amyloidosis in the northernmost region of Sweden: a retrospective cohort study

Abstract

Introduction: Epidemiological data on hereditary transthyretin (ATTRv) amyloidosis from the northernmost region of Sweden (Norrbotten) are sparse.

Methods: We reviewed the medical records of all incident cases of ATTRv amyloidosis in Norrbotten between 2006 and 2018. Official population and mortality statistics were used to estimate incidence rates and standardised mortality ratios (SMRs).

Results: Ninety-three patients were diagnosed with ATTRv amyloidosis between 2006 and 2018 (median age, 72.8 years; 68.8% men; 95.7% Val30Met [p.Val50Met] mutation). The incidence rate per 100,000 persons and year increased from 1.50 (95% confidence interval [CI], 0.84-2.47) cases in 2006-2009 to 4.92 (95%CI, 3.46-6.78) cases in 2016-2018. The SMR in the ATTRv amyloidosis cohort was 2.64 times higher than in the general population in 2006-2018 (95%CI, 1.78-3.77). However, there were indications of lower SMRs over time (2006-2012, 2.96 [95%CI, 1.73-4.74]; 2013-2018, 2.32 [95%CI, 1.23-3.96]) and by use of disease-modifying drugs (no, 3.21 [95%CI, 1.87-5.13]; yes, 2.09 [95%CI, 1.08-3.64]).

Conclusion: The incidence of ATTRv amyloidosis increased 3-fold in Norrbotten between 2006 and 2018, most likely due to a previous underdiagnosis - with suggestions of lowered mortality during later years, possibly due to the introduction of disease-modifying drugs.

Keywords: Amyloid; Sweden; amyloidosis; epidemiology; hereditary; transthyretin.