Objective: To explore the association of hepatocellular carcinoma (HCC) with environmental factors through analyzing birth order data from pedigree sibships.
Methods: A birth order study was conducted based on the methods of Greenwood and Haldane for 100 probands and 22 affected siblings from 100 pedigrees in a cohort which was followed up for 8 years in Haimen, Jiangsu, China.
Results: The findings from the Greenwood method suggested that there was a tendency for cases of HCC to concentrate at lower birth orders of 1 to 3. With the effects of hepatitis B virus on the birth orders being controlled, the same tendency was also observed. The results from Haldane method showed that difference between actual value and expected value of 6A was more than the double standard deviation. Sigma 6A(actual value) = 1,806, Sigma 6A(expected value) = 1,988, the absolute value of (Sigma 6A(actual value) - Sigma 6A(expected value))/the square root of Sigma V6A = 2.1657 (0.02 < P < 0.05). The actual value of 6A was lower than the expected value of 6A suggesting that individuals at lower birth orders were at a higher risk of suffering from HCC. In addition, through data from ecologic research, there was a decreasing tendency of mortality of HCC within 10 years after the prevalence of tap water in Haimen city. The correlation coefficient by Spearman test was -0.818 (P < 0.01). The contribution of the quality of drinking water in the locality to the onset of HCC was found among people born in earlier period.
Conclusions: There was a tendency that the onset of HCC cases concentrating was at lower birth orders in this research, which was inconsistent with several reports of foreign authors' which showed a reverse tendency. According to the ecological results, it was suggested that long-term drinking of ditch-water was responsible for the tendency of cases of HCC concentrating at lower birth orders. There were also certain effects of environmental factors exerted on the onset of HCC being discovered.