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

Objective This study aimed to examine the incidence rates of diagnosed anorexia nervosa (AN) and bulimia nervosa (BN) and their variations over time in Taiwan. Method The data of individuals with AN and BN, as defined by the International Classification of Diseases, Ninth Revision, Clinical Modification's (ICD-9-CM), were extracted from merged databases by means of unique identification numbers. To fulfill the criteria of incident cases, individuals must not have had an AN or BN diagnosis in the preceding 2 years. The time trends were analyzed using Joinpoint regression analysis. Results The overall AN and BN incidence rates were 1.1 and 6.1 per 100,000, respectively. There was no significant change in the overall incidence rate for AN or both sexes across the study period. A significant increase in AN incidence occurred in the age groups of 10-14 and 30-39 years. The overall incidence rate of BN increased significantly in the few years before 2009 and then decreased. A similar trend occurred among the females and groups aged above 20 years. There was no significant change in the overall BN incidence rate over the whole period. Discussion Compared with Western countries, the AN incidence in Taiwan is very low, whereas the BN incidence is in the lower end of the range. The findings that the age of the first-time detected AN and BN is older in Taiwan and that the significant increases in age-specific incidence are mainly among adults suggest that more effort is needed to detect individuals with AN and BN at a younger age in Taiwan.