Incidence rates of eating disorders

Anorexia Nervosa
The incidence rate of anorexia nervosa was 8.1 per 100 000 person during 1985-1989. 63% of the incident cases were referred to mental health care, accounting for an incidence rate of anorexia nervosa in mental health care of 5.1 per year per 100 000 population.

Incidence rates of anorexia nervosa are highest for females 15-19 years old. These constitute approximately 40% of all identified cases and 60% of female cases. The incidence rate of 73.9 per 100 000 person for 15-19 years old, 9.5 for 30-39 year old women, 1.8 for 50 to 59 year old women and 0.0 for women 60 years and older. The majority of male incidence rates reported were below 0.5 per 100 000 population per year.

There is an upward trend in the incidence of anorexia nervosa since the 1950s. The increase is most substantial for women of 15-24 years old with an estimated rate of increase of 1.03 per 100 000 person oer calender year. In 10-14 year old girls a rise in incidence was observed for each decade since the 1950s. The rates for men and for women 25 and older remain relatively low.

Bulimia Nervosa
There have been few incidence studies for bulimia nervosa due to the lack of criteria of bulimia nervosa in the past. Therefore, it is difficult to examine trends of bulimia nervosa or a possible shift from anorexia nervosa to bulimia nervosa. It is reported that there is an annual incidence of bulimia nervosa around 12 per 100 000 population. During the years 1988-1993 the primary care incidence of anorexia nervosa in the UK remained stable, but the incidence of bulimia nervosa increased threefold. In 2000 primary care incidence rates were 4.7 and 6.6 per 100 000 population for anorexia and bulimia nervosa, respectively. The incidence of anorexia nervosa remained remarkably consistent over the period studied. Overall there was an increase in the incidence of bulimia, but rates declined after a peak in 1996.

Over the period studied, annual incidence rates for diagnosed anorexia nervosa remained stable for females aged 10-39 years. The rate in 1988 was 18.5 per 100 000 and in the year 2000 the rate was 20.1 per 100 000. In 2000 the age- and gender-adjusted incidence of anorexia nervosa diagnosed in primary care was 4.7 per 100 000 population. The incidence rate for females was 8.6 per 100 000 compared with 0.7 per 100 000 for males. This translated to a relative risk for females to males of 12:1. The highest incidence, 34.6 per 100 000 population, was found in females aged 10-19 years. The results for bulimia nervosa are very different.

The early 1990s showed a marked increase in primary care incidence for women aged 10-39 years which continued until 1996. Although there was an overall increase in reported cases of bulimia nervosa from 1988-2000, the incidence rate has fallen by 38.9% since this peak. In 2000 the age- and gender-adjusted incidence of bulimia nervosa in primary care was 6.6 per 100 000. The incidence rate for females was 12.4 per 100 000 compared with 0.7 per 100 000 for males. This represents a relative risk for females to males of approximately 18:1. The highest incidence, 35.8 per 100 000 was in females aged 10-19 years.

Binge eating
The prevalence for binge eating disorder dropped from 1.5% in 1990 to 0.7 in 1997 in women and from 2.4% to 1.5% in men.

Social class
Most eating disorders particularly bulimia nervosa show a higher prevalence in the lower socio-economic classes.

Urbanisation/Industrialization
The incidence rate per year per 100 000 women-years (age 5–64 years) for anorexia nervosa was 17.4 in rural areas, 20.2 in urbanised areas and 11.5 in large cities. Bulimia nervosa showed an incidence rate of 7.0 in rural areas, 16.7 in urbanised areas and 25.5 in large cities. The incidence of bulimia nervosa was almost two and a half times higher in urbanised areas than in rural areas and five times higher in large cities than in rural areas. It can be concluded that urban life is a potential environmental risk factor for bulimia nervosa but not for anorexia nervosa.

References:
http://books.google.com.my/books?id=YGX3luPHXqEC&pg=PA79&lpg=PA79&dq=incidence+rate+eating+disorders&source=bl&ots=xjsHonJqQY&sig=ZBdHtXt9SYvpCAFmt0Yo7QJude0&hl=en&ei=FPZlStv2IYPVkAWqxKHNDg&sa=X&oi=book_result&ct=result&resnum=10

http://bjp.rcpsych.org/cgi/content/full/186/2/132

http://bjp.rcpsych.org/cgi/content/full/189/6/562