Chinese Medical Journal 2000;113(1):31-34
A large scale epidemiological survey of Graves’ disease in Daqing area

LI Yanbo 李艳波 ,  LI Changqi 李昌祁 ,  YIN Huiqing 阴慧清

LI Yanbo 李艳波 (Department of Endocrinology, the First Clinical Hospital of Harbin Medical University, Harbin 150001, China)

LI Changqi 李昌祁 (Department of Endocrinology, the First Hospital of Daqing, Daqing 163001, Heilongjiang Province, China)

YIN Huiqing 阴慧清 (Department of Endocrinology, the First Clinical Hospital of Harbin Medical University, Harbin 150001, China)

Correspondence to:, (Tel: . Fax:. E-mail:)
Keywords
Graves’ disease ; associated factors ;epidemiology
Abstract
Objective To study the incidence of Graves’ disease and the associated factors.
Methods Totally 100 123 people aged 15 to 79 years in Daqing area were surveyed epidemiologically.The investigation was conducted for two years.
Results
All 301 patients with Graves’ disease were first diagno
sed, with 74(1.6‰) males and 227(4.1‰) females. The total incidence was 3.0‰, showing significant differences between ages and between occupations. Investigation of 18 associated factors for Graves’ disease by using the logistic multivariate regression analysis showed the pathological factors of the virus infection history, psychological stimulation, food, drugs, family history, education and distribution.
Conclusion
This study may suggest the theoretical evidence for
prevention and treatment of Graves’disease.

We studied the present epidemiological situation and major pathological factors of Graves’ disease on 100 123 people in Daqing area from May 1993 to May 1995 with the results reported as follows.

METHODS

The general situation of surveyed area
Daqing area lies in the middle of Songnen plain in Heilongjiang Province, with geographical position on east meridian 124°19’~125°12’ and north latitude 45°46’~46°55’.

There is a total of 2 362 000 people in Daqing area. Of them, 1 034 000 live in cities, and 1 328 000 are peasants. The area is divided into 4 parts: oil processing, oil exploiting,culture and economy,agriculture and pastoral areas.

The subjects
The 1 000 123 people aged over 15 years were surveyed in Daqing area. Of them, 59 571 are urbanites; 42 552 live in agriculture and pastoral areas. All people were divided into 10 age steps, with male 45 608, and female 54 515 ( Table 1 ).

The survey methods
The survey plan was drawn up according to the inter-national clinical epidemiological survey patterns and methods by the guide and help of epidemiologist in Public Health College of Harbin Medical University, while the subjects and groups were chosen and statistical survey items were calculated in the light of basic epidemiological survey fomulas. During the survey,the method of clustering stratified sampling was used in order to prevent deviation. The test paper was applied among the workers, family members, students, peasants and herdsmen in the large-scale and middle-size enterprises, agriculture and pastoral areas.

The cooperation group consisted of three parts. The first part was composed of the experienced doctors in 1 grade first rate hospital (for example: Daqing Shanhuan General Corporation Worker Hospital), with the job to mobilize, inquire and fill in the survey form. The second part was composed of the visiting staff, the associate professor of 2 grade first rate hospital (for example: The 5th Hospital of Daqing) whose duty was to examine the survey form, carry on the physical examination and fill the register form. The third part was composed of professors, associate professors of endocrinological department of 3 grade first rate hospital (the First Clinical Hospital of Harbin Medical University and the First Hospital of Daqing) whose duty was to guide, answer the questions and finally confirm the diagnosis.

The suspicious patients diagnosed by disease history and physical examination should be subjected to the measurement of total triiodothyronine (TT 3 ) and total thyroiodine (TT 4 ) in serum and thyroid iodine-131 absorbable rate. And those uncertain cases were diagnosed by the endocrinologists after determining the free triiodothyronine (FT 3 ), free thyroiodine (FT 4 ), thyroglobulin antibody (TGA), thyromicrosome antibody (TMA), thyrotropin (TSH) and thyroid γ-scan or B-ultrasonography.

During the history survey,the patients who had family history were registered emphatically. The cases of having medication history of iodine salt, iodine food or drugs referred to those with an intake over 150 μg per day for over one month.

By laboratory experiment method, the normal data and coefficient of variation (cv%) of TT 3 (1.5~35.1 nmol/L) and TT 4 (46~181 nmol/L)were determined by radio-immunoassay.

FT 3 (3.19~9.15 pmol/L) and FT 4 (9.11~25.47 pmol/L) were determined by direct method (radio-immunity kit), and the kits used were afforded by Atomic Energy Institute of Chinese Academy.

TSH (<10 mU/L) was determined by double antibody radioimmunoassay, with the kits afforded by Beifang Reagent Institute of Chinese Isotope Corporation.

TGA(<30%) and TMA(<20%) were determined by double antibody radioimmunoassay. The kits were afforded by Shanghai Biological Institute of the Ministry of Health.

Thyroid iodine-131 absorbable rate was regarded as normal under 25% at the third hour and under 50% at the 24th hour.

Thyroid γ-scan was determined by cGA-40A γ-scanner made by Toshiba, Japan.

Thyroid B-ultrasonography was performed by Performa multifunction linearity electronic B-ultrasound diagnosis apparatus made in America and the frequency of explorer was 7.5 MHz.

Statistical analysis
The data were the qualified materials,presented as mean±S mean . Statistical analysis was made using t test or x 2 test. Logistic multivariate regression analysis was performed to all the material compiled in dBASE-Ⅲ data base by computer.

RESULTS

Graves’ disease incidence
Totally 100 123 people were surveyed epidemologically, and 3855 suspicious patients sifted by asking history and physical examination had measurement of TT 3 , TT 4 and thyroid iodine-131 absorable rate. Of them, 493 were diagnosed as hyperthyroidism, giving the suspicious and diagnostic rates of 38.5‰ and 4.9‰ respectively in 100 123 people, and the diagnosed hyperthyroidism rate was 128‰ in the suspicious patients. 301 were newly diagnosed as Graves’disease in the surveyed people, giving a total morbidity of Graves’disease of 3.0‰.

The percentages of Graves’disease,nodular goiter, autonomic high function thyroma, obviously increased TGA, TMA and the others were 61.05%, 30.02%, 0.65%, 0.81% and 8.12% respectively in the diagnosed hyperthyroidism.

Factors associated with Graves’disease
Sex: among patients with newly diagnosed Graves’ disease, 74 were males (1.6‰) and 227 females (4.1‰), giving a ratio (male:female) of 1∶4.

Age: the number and incidence of Graves’ disease in different age steps were shown in Table 1.

Education: the education of the surveyed people was shown in Table 2 .

The incidence of city inhabitants was 2.68‰, and of the countryside inhabitants was 3.52‰, being significant in statistical analysis ( Table 3 ).

The incidences were different from regions of oil processing, oil exploiting, and cultural and economic conditions and agricultural and pastoral regions ( Table 4 ).

Eight pathological factors were chosen in logistic regression equation by computer. They were: education (x 4 , region (x 7 , family history (x 8 , iodine salt (x 9 , iodine foods (x 10 ), iodine drugs (x 11 ), virus infection (x 15 and psychological stimulation (x 17 ) ( Table 5 ).

DISCUSSION

At present, few epidemiological surveys and studies of Graves’ disease were reported at home and abroad. And the report of more accurate incidence of Graves’ disease was also rare.

The 301 patients with Graves’ disease were diagnosed in the surveyed people during a period of two years, giving an incidence of 3.0‰, showing that Graves’ disease is not rare.

Among the newly diagnosed patients,sex proportion (male:female) was 1∶4, which was approximately equivalent to the reports from foreign countries.[1,2]

The study showed that the peak age was 40-50 years (male) and 30-35 years (female). The incidence had significant differences between ages (P<0.01). Our study also showed that the incidence is high in people with higher level of education (P<0.01), that there appeared significant differences between urbanites and suburbanites (P<0.01). So was the regional distribution (P<0.001). The causation remains to be studied and discussed in the future.

Recently, more researches have been focused on Graves’ disease multiple etiological foctors.[3,4]Our study proved that there were 8 etiological factors for Graves’ disease: education, regional distribution, family history, iodine salt, iodine food, iodine drugs, virus infection and psychological stimulation. All these factors were statistically signficant (P<0.01) and set into the logistic regression model at the end. This may serve as the theoretical evidence for prevention and treatment of the Graves’ disease.

Among the above factors, infection and regional distribution have been further studied in foreign countries.[5,6]It should also be the emphasis for us.

Acknowledgement: We warmly thank professors Lu MJ and Guan DM (Public Health College of Harbin Medical University) for their assistance in statistical analysis.

REFERENCES

1. Lian ZJ. Epidemiology. 2nd ed.Beijing: People’s Health Publishing House; 1994:54-55.
2. Lungu G, Zosin I, Milos A, et al. Epidemiological aspects of Graves-Basedowu’s disease. Endocrinology 1988;26:107-111.
3. Berglund J, Christensen SB, Hallengren B. Total and age-specific incidence of Graves’ thyotoxicosis, toxic nodular goitre and solitary toxic adenoma in Malmo 1970-1974. J Intern Med 1990;227:137-141.
4. Kalk WJ, Kalk J. Incidence and causes of hyperthyroidism in blacks. S Afr Med J 1989;75:114-117.
5. Brownlie BE, Wells JE. The epidemiology of thyrotoxicosis in New Zealand: incidence and geographical distribution in north Canterbury 1983-1985. Clin Endocrinol 1990;33:59.
6. Tamai H, Uno H, Hirota Y, et al. Immunogenetics of Hashimoto’s and Graves’ diseases. J Clin Endocrinol Metab 1985;60:62-66.