Time trends in lifetime incidence rates of first-time diagnosed anorexia nervosa and bulimia nervosa across 16 years in a danish nationwide psychiatric registry study

Abstract

OBJECTIVE To study recent time trends in the incidence of diagnosed anorexia nervosa (AN) and bulimia nervosa (BN) based on nationwide psychiatric register data. METHOD The Danish Psychiatric Central Research Registry was used to identify the incidence of diagnosed cases with AN and BN at the ages of 4-65 years from 1995 to 2010. Age- and sex-adjusted incidence rates per 100,000 person-years were calculated and were adjusted for time trends in the total number of people diagnosed in psychiatry. Time trends were analyzed using JoinPoint regression analysis. RESULTS A total of N = 5,902 persons had a first-time incidence of AN, and a total of N = 5,113 had first-time incidence of BN. Incidence rates increased for AN from 6.4 to 12.6 per 100,000 person-years, and for BN from 6.3 to 7.2 per 100,000 person-years. In 2010, the male-to-female ratio was 1:8 for AN, and 1:20 for BN. There was an earlier onset for AN than for BN, and age at incidence decreased during the observation period for AN but not for BN. A sizeable part of the increasing incidence rates for AN and in particular, the younger AN age groups, could be attributed to an increase in the total number of N = 249,607 persons with first-time diagnoses in psychiatry. DISCUSSION Incidence rates had increased slightly for AN, but were stable for BN across 16 years in this nationwide study and to a large extent were reflective of a general increase in diagnosed mental disorders. (Int J Eat Disord 2015).