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

Abstract

Objective: 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 healthcaredetected anorexia nervosa (AN) and bulimia nervosa (BN) from 2010 to 2016. Methods: 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.Results: 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.Discussion: 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. K E Y W O R D Sanorexia nervosa, bulimia nervosa, epidemiology, incidence, Joinpoint, time-trends The question of whether the incidence, or annual diagnostic rate, of anorexia nervosa (AN) and bulimia nervosa (BN) has increased over the past decades is a subject of debate. Long-term epidemiological data are valuable, yet challenging to obtain and interpret, and disposed to known methodological challenges (see Hart,

Rates and trends in healthcare‐detected incidence of anorexia nervosa and bulimia nervosa: A national health insurance claim data study in Taiwan, 2002–2013

“…The age at first‐time diagnosis of BN peaked at 20–29 years in our study, which is older than that in most European countries (Micali et al, ; Smink et al, ; Steinhausen & Jensen, ). Similar to AN, the percentage of the incident BN cases who were older than 30 years in Taiwan was also higher than in Western countries (47% vs. 15–30%) (Micali et al, ; Reas & Ro, ; Steinhausen & Jensen, ). There was a steep increase in the incidence rates of BN in the age groups of 30–39 years and 40–49 years in addition to a small increase in the 20–29 years age group from 2002 to 2007 or 2009.…”

“…Whether the incidence of eating disorders (EDs) has changed over time has been a subject of debate (Smink et al, ). Earlier case register studies showed that the incidence of anorexia nervosa (AN) increased before the 1970s (Hoek, ; Keel & Klump, ), whereupon it seemed to stabilize throughout the 2000s (Currin, Schmidt, Treasure, & Jick, ; Smink et al, ; Steinhausen & Jensen, ; Van Son, Van Hoeken, Bartelds, Van Furth, & Hoek, ) and 2010s (Currin et al, ; Keel & Klump, ; Reas & Ro, ; Steinhausen & Jensen, ). Furthermore, studies indicated that after an initial surge in the bulimia nervosa (BN) incidence in the 1980s (Smink et al, ) and 1990s (Currin et al, ), it stabilized (Micali, Hagberg, Petersen, & Treasure, ) or decreased (Currin et al, ; Reas & Ro, ; Smink et al, ) during the 2000s and 2010s.…”

“…Studies of the recent trends in the incidence of EDs have largely been based on primary care (Currin et al, ; Micali et al, ; Smink et al, ; Turnbull, Ward, Treasure, Jick, & Derby, ; Van Son et al, ) and psychiatric registers (Javaras et al, ; Micali et al, ; Reas & Ro, ; Steinhausen & Jensen, ). Primary care studies have found that the AN incidence remained stable, with 4.7 per 100,000 population and 6.0 per 100,000 person‐years in the United Kingdom and the Netherlands, respectively (Currin et al, ; Smink et al, ).…”

“…In Sweden, a study found considerable increases in AN after the year 2000 (Javaras et al, ). The overall incidence rates of narrowly and broadly defined AN were stable from 2010 to 2016 (18.8–20.4 per 100,000 for narrow AN) in Norway, whereas the overall rates of BN declined (18.5–16.1 per 100,000 for narrow BN) (Reas & Ro, ).…”

“…Epidemiological studies showed that the incidence or prevalence of BN surpassed that of AN in the 1990s and 2000s (Currin et al, ; Steinhausen & Jensen, ), after which the incidence of BN decreased. In recent decades, the incidence of these two disorders has approached equal or even been in reverse order of frequency; that is, the incidence of AN has been higher than that of BN in Denmark, Holland, and Norway in most recently published studies (Reas & Ro, ; Smink et al, ; Steinhausen & Jensen, ).…”