Time trends in healthcare-detected incidence of anorexia nervosa and bulimia nervosa in the Norwegian National Patient Register (2010-2016).

Abstract

Few studies have investigated temporal trends in the incidence of eating disorders (EDs). This study investigated time trends in the age- and sex-specific incidence of healthcare-detected anorexia nervosa (AN) and bulimia nervosa (BN) from 2010 to 2016. Data were retrieved from the Norwegian National Patient Register as defined by the International Classification of Diseases (ICD-10): narrowly defined AN (F50.0), broadly defined AN (F50.0 + 50.1), narrowly defined BN (F50.2), and broadly defined BN (F50.2 + 50.3). The average annual percent changes (AAPCs) in incidence rates (IRs) were examined by Joinpoint regression analyses. The overall (i.e., both genders, ages 10-49) rates of AN were stable across the 7-year period, with IRs ranging from 18.8 to 20.4 per 100,000 for narrowly defined AN and 33.2 to 39.5 per 100,000 for broadly defined AN, whereas overall rates of BN declined. Age- and gender-stratification revealed a significant average annual increase in AN (narrow and broad) among 10- to 14-year-old girls. The incidence of broadly defined AN also increased significantly among females aged 15-19 years between 2010 and 2012, before leveling off. Nearly universal declines in the incidence of narrowly and broadly defined BN among females occurred. IRs among males were stable and comparatively low, with no significant trends toward increasing or decreasing rates of AN or BN over time. Although register-based studies provide an underestimate of the true incidence and may not accurately reflect population-level changes in true ED occurrence, this study extends our knowledge regarding trends in the detected incidence of EDs into the second decade of the 21st century.