SECULAR TRENDS IN THE INCIDENCE OF ANOREXIA-NERVOSA - INTEGRATIVE REVIEW OF POPULATION-BASED STUDIES

Objective and Method: Aggregating across retrospective cohort samples, this integrative review synthesizes the findings of 12 cumulative inc idence studies (45 hypotheses) on anorexia nervosa secular trends. Res ults: (I) The female/male anorexia incidence rate ratio was estimated to be 8.20, 18.46 versus 2.25 cases per 100,000 per year, p < .05; (2) female teenagers experienced anorexia at a rate fivefold greater than other women, 50.82 versus 10.37 incident cases per 100,000 per year, p < .001; (3) no secular trend or change in the incidence of anorexia was observed among teenagers, while a near threefold increase was obse rved or:er the past 40 years among women in their 20s and 30s, 6.28 (1 950-1964) versus 17.70 (1980-1992) cases per 100, 000 per year, p < .0 5; and (4) the two cohort characteristics of age, and the age by year interaction accounted for nearly two thirds of the variability among a norexia incidence estimates, R-2 = .614, F(2,27) = 21.49, p < .001. Af ter the two factors of age and the Age x Year interaction were account ed for, none of the other study characteristics, including study year( s) were found to be significantly associated with anorexia incidence, that is, a main effect of time was not observed Discussion: The integr ative evidence across the population-based epidemiologic studies cover ing 40 years in this field suggests strongly that, overall, the incide nce of anorexia nervosa, particularly among those very young women at greatest risk of experiencing it, has not increased significantly. How ever, the risk does seem to have increased significantly among women i n their 20s and 30s. (C) 1998 by John Wiley & Sons, Inc.