OBJECTIVETo observe the serial changes of condition and related factors of Keshan disease (KSD) and provide the scientific basis for disease control and further research.

METHODSThe villages in KSD epidemic area of Juxian, Yishui, Pingyi, Zoucheng counties were selected. Since 1990, every five-year was counted as a stage. For the first to third stage, 3-14 year-old residents and over 14 year-old suspicious patients were selected as surveillance subjects. And in the fourth stage, all residents were selected as surveillance subjects. The same group of surveillance subjects in each stage were observed consecutively for 5 years. Surveillance contents included physical checkup, electrocardiogram (ECG) and Xray. At the same time, the selenium (Se) concentration in hair, wheat, corn and sweet potato was measured. The economic income and grain availability were also investigated.

RESULTSTotally, 14,510 cases were visited during 18 years. The incidence of KSD was 3.02% in the first stage, 2.31% in the second stage, 3.57% in the third stages and 3.65% in the fourth stage. Totally, 14,510 cases were examined by ECG, 809 cases showed the abnormal ECG and the total incidence of abnormal ECG was 5.49%. The incidence of abnormal ECG was 3.52% -5.24% from 1990 to 2004 but was 10.97%-10.91% from 2005 to 2007. 732 of hair samples, 701 of wheat samples, 615 of corn samples and 643 of sweet potato samples were collected and the Se concentration was determined by the fluorescent method. Se levels in hair samples had increased (P < 0.05) year by year but Se levels in food have not changed significantly. The economic income and grain availability had increased gradually from 535.8 yuan and 254.6 kg per person in 1990 to 2968.0 yuan and 602.0 kg per person in 2007.

CONCLUSIONThe condition of KSD was in a stable situation in Shandong Province. Related factors improvement should be an important environmental condition.