50-Year Trends in Rochester,

in the Incidence of Anorexia Minn.: A Population-Based

Alexander R. Lucas, Michael O’Fallon, Ph.D.,

w.

Objective: long-term

The aim of the trends in incidence

community

of Rochester,

M.D., C. Mary Beard, M.P.H., and Leonard T. Kurland, M.D.,

study was of anorexia

Minn.,

to determine nervosa by

during

the 50-year

disorder. Method: From a community-based with diagnoses ofamenorrhea, starvation, were

screened

diagnostic f ulfilled

to

identify

true

cases

of

anorexia

nervosa

eighty-one nervosa;

954

increased

and

to 26.3

in 1 980-1

and for males remained The overall age-adjusted

determined

residents these were

had

the

by

using

(1 66 female the incidence

standard

and 1 5 male) cases. Due to

among

J Psychiatry

females 1991;

Foundation,

I 5-24

Rochester,

print requests to Dr. Lucas, Mayo Clinic, ester, MN 55905. Supported in part by grant NS-17750

of Neurological The authors

and thank

in screening

Hultz for checking merable diagnostic analysis. © 1991

Psychiatry

Communicative Judy K. Stand medical

records,

200

years

from

the

Disorders and Joanne Laurie

Psychiatric

1 48: 7, July

1991

Minn. First

Address

St.,

old

5.W.,

National

reRoch-

Institute

and Stroke. C. Ward for assis-

E. Jones

residency, James R. Wentz lists, and Shauna L. Stensrud American

incidence 15-24 100,000

rates

for

women

years old, person-years

20 years there was a was 14.6

but

not

among

older

women

or among

males.

148:917-922)

Received July 3, 1990; revision received Dec. 3 1, 1990; accepted Feb. 4, 1991. From the Section of Child and Adolescent Psychiatry, the Section of Clinical Epidemiology, and the Section of Biostatistics,

Mayo

The

For females rate per

and I .8 for males. The prevalence rate per 1 00,000 population was 269.9 for 22.5 for males. Conclusions: Anorexia nervosa is more common than previously Among girls I 5-1 9 years old it is a very common chronic illness. Its incidence

norexia nervosa has become an important health problem in Western countries (1). It is associated with severe long-term morbidity and substantial mortality (2-5). Debate has focused on whether the mcidence of anorexia nervosa is increasing (6-9). Incidence represents the number of new cases appearing during a time interval, usually expressed as the number of cases pen 100,000 person-years (same as cases pen year pen 100,000 population). Prevalence represents the total number of cases of the disease in a group at a certain time expressed as the rate per 100,000 population on as a percentage. Most estimates have sug-

and

984.

constant. incidence

A

J

who

increased

(Am

Am

1 984

in 1 950-1

recognized.

statistical Copyright

1 935 through

in the rates for girls 1 0-i 9 years old, the incidence rate among female 1 6.6 per 1 00,000 person-years in the 1 935-1 939 period to a low of 7.0

has

tance

period

and prevalence rates and all persons residing in the

a quadratic trend residents fell from

f or females f emales and

Clinic

incidence identifying

Dr.P.H.

epidemiologic resource, 13,559 medical records weight loss, anorexia nervosa, or other conditions

criteria. Results: One hundred the diagnostic criteria for anorexia

old and older linear increase.

Mayo

Nervosa Study

and

for searching for assistance

Association.

Karen

S.

innuin the

gested

an increase in the incidence of anorexia nenvosa 1950 (10-17) and perhaps since 1930 (18). Although most clinicians interpreted greater numbers of patients with anorexia nervosa seen in practice as signifying a remarkable increase in the occurrence of the disorder, Williams and King (7) in England and Nielsen (19) in Denmark concluded that the apparent rise in anorexia nervosa was not real but was related to changes in demographics and in medical practice. Our population-based study of the incidence of anorexia nervosa in Rochester, Minn., during the 45-year penod 1935-1979 (8) failed to reveal a significant trend and identified surprisingly high rates during the 15year interval between 1935 and 1949. A trend toward an increase in the rates for girls 10-19 years old, albeit not statistically significant, was noted for the period 1950-1979. A considerable increase in incidence in females with the illness during the final 2 years of the study was a compelling reason to extend the study for another S years to determine whether that trend would continue. Rochester is a Midwestern city located about 75 miles southeast of Minneapolis. It is the county seat of Olmsted County, a grain and dairy farming region. its population was approximately 60,000 in 1985 and since

917

SO-YEAR

TRENDS

IN

ANOREXIA

TABLE 1. Diagnostic Categories Reviewed to Identify Anorexia Nervosa in Rochester, Minn., 19351984a

Diagnostic

Number Recoras Screened

Category

Anorexia

nervosa

Amenorrhea Oligomenorrhea Anovulation, irregular menstruation, menstrual dysfunction

dysfunction,

anism Delayed

puberty,

delayed

malnutrition diet disturbance,

Anasarca,

edema,

Addison’s

disease

Simmonds’ Malaise

b213

incidence

peared

in more

97

42.0

15

1.8

70 14

1.8 1.6

2,120

and than

Nervosa

70 60 Cl)

0 Females

5O

OMales

ci

(N

166)

=

(N=15)

C) .340

.30 2O

S

0.2

3

0.5

L

10 0

menar-

1 2

428 181

0-

5-

10-

4

9

14

:::

1519

2024

:

25- 30- 35- 4029

34

Age

0.2 1.1

39

44

4549

5054

5559

60

(years)

under1,483 1,775 marasmus

psychogenic disorder

Mayo

FIGURE 1. Distribution of Age at Diagnosis of Anorexia Among Female and Male Residents of Rochester, Minn.

z

51 4

3.4 0.2

377 138

0 0

0.0 0.0

54

0

0.0

52 61

1 0

1.9 0.0

344

1

0.3

12 203

0 0

0.0 0.0

disease

from

%

826

hydrops

Nervous exhaustion Nervous stomach, gastrointestinal Vomiting are

N

3,789 878

607

weight, Inadequate Nutritional

“Data

or

hypo-ovari-

che Delayed menstruation Starvation, weight loss,

Total

Cases of Anorexia Nervosa Identified

231

Anorexia

Ovarian

All Cases of

Clinic prevalence one

records

and

cases

were

diagnostic

13,559 other

sources.

identified;

1.9

264b

some

ap-

category.

23,000 in 1935. Although the local economy once was based chiefly on farming and light industry, the Mayo Medical Center and IBM are now the largest employens in the city. The homogeneous population is pnimarily of northern European origin. In 1980, the racial composition was 98% white. Compared with the U.S. population, there was a relatively greater proportion of female residents between the ages of 15 and 25 years.

tients had never been hospitalized for their illness, and many had not seen a psychiatrist. Records with diagnostic coding for depressive illnesses were not screened separately, although many of the anorexia nervosa patients had depressive symptoms and some developed major depression after the onset of anorexia nervosa. The depressed patients who had notable weight loss or menstrual dysfunction appeared on those diagnostic lists and thus were identifled as potential anorexia nervosa cases. Diagnostic certainty was rated as definite, probable, and possible on the basis of the completeness of the information available in the records. When incidence data were analyzed separately for these groups, for the first 45 years of the study the trends did not differ appreciably from the overall trend for all subjects cornbined (8). Therefore, we combined the groups to analyze data for the entire 50-year span of the study. Criteria were applied consistently throughout the duration of the study, maximizing the likelihood that a comparable group of subjects was identified over time. The background of the study and the Mayo Clinic epidemiologic archives have been described previously

(8, 21, 22). METHOD The medical records in the Mayo Clinic epidemiologic archives and in the files of other health-cane providens in the surrounding geographic area were exammed for residents of Rochester, Minn. We screened for approximately 30 diagnostic terms and particularly for amenorrhea, oligomenorrhea, starvation and weight loss from any cause, and anorexia nervosa (table 1). For patients with these diagnoses the original medical records were reviewed and the diagnosis of anorexia nervosa determined or confirmed by using DSM-III-R and the criteria of the Pathology of Eating Group (20). Thus, we were able to identify a large number of patients not previously diagnosed as having anorexia nenvosa. Those who were so diagnosed previously but did not meet the criteria were excluded. Most of these pa-

918

Tests of trends using generalized structure. Tests of freedom, and freedom.

in incidence rates were performed by linear models (23) with Poisson error for linearity of trend have one degree quadratic models have two degrees of

RESULTS During the 50-year period 1935-1984, 166 females and 15 males who had been residing in Rochester for at least 1 year developed anorexia nervosa. The mean± SD age at diagnosis of the females was 21.7±8.3 years (median=19 years, nange=10-57 years); for the males it was 20.9±9.0 years (median=18 years, range=1249 years). The age distribution is shown in figure 1. Age-adjusted (to the 1970 U.S. white population) incidence rates by S-year periods are shown in figure 2.

AmJPsychiatry

148:7,July

1991

LUCAS,

FIGURE 2. Age.Adjusteda Incidence Rates for Anorexia Nervosa in Female and Male Residents of Rochester, Minn., by 5-Year Periods

11 35

-

30

-

BEARD,

O’FALLON,

ET AL.

FIGURE 3. Age-Specific Incidence Ratesa for Anorexia Nervosa, by 5-Year Periods, in Two Age Groups of Female Residents of Rochester, Minn.b

U)

Females

S-S

(N

=

166)

j

le,15,//

200-

-.-Age

10-19

Age 20-59

-0-

.

S S S S

19351939

19401944

19451949

1950-

1955-

1954

1959

5-year

19601964

19651969

. period

1970-

1975-

1980-

1935-

1974

1979

1984

1984

to

1970

U.S.

white

I

I

1935-

19401944

‘ -

Nervosa

Incidence per 100,000 Person-Years Age Group (years) Females Males ________________________________________________________

Total

0-9 10-14

0.0 25.7

0.0 3.7

0.0 14.6

15-19

69.4

7.3

43.5

20-24

27.6

2S-29

50-59 60 and older Total aAge.adjusted

(to

1970

20.7 10.9 5.2 2.0 0.0 15.1 U.S. white

1.8.

Age-

and

_

14.6;

males,

population)

sex-adjusted

rate:

4.6

19.9

3.6 0.0 1.0 0.0 0.0 1.7 rates:

13.0 5.6 3.2 1.1 0.0 9.0

on

a log

bObseedcircles,

Psychiatry

148:7,

1954

July

I

I

I

1955-

19601964

19651969

1959

200

-

100

-

1991

I 19701974

I 19751979

I 19801984

period

scale.

predicted=lines.

FIGURE 4. Age-Specific Incidence 5-Year Periods, in 15-24-Year-Old Minn.”

Ratesa for Anorexia Nervosa, by Female Residents of Rochester,

Cl) C

.5

10

8.2.

5

J

0

females,

The overall age-adjusted incidence rate for females was 14.6 pen 100,000 person-years; for males it was 1.8 per 100,000 person-years. Thus, anorexia nervosa was found 8.1 times more frequently in females than in males. The overall age- and sex-adjusted rate was 8.2 per 100,000 person-years. Age- and sex-specific mcidence rates are shown in table 2. The incidence rates for females 10-19 years old and 20-59 years old are shown in figure 3. The age-adjusted incidence rates of anorexia nenvosa in females residing in Rochester have increased from a low of 7.0 pen 100,000 person-years in 19501954 to a high of 26.3 in 1980-1984. This increase is due primarily to the highly significant linear trend in the incidence rates for females 10-19 years old (p< 0.001). The estimated coefficient indicates that, on the average, the incidence rates increased by 36% every S years over the 35 years from 1950 to 1984. When the entire scope of the study is considered (1935-1984), the incidence rates for females 10-19 years old show a highly significant quadratic trend (p