Main Source of Drinking Water and Familial Aggregation of Kashin-Beck Disease: A Population Based on Case-Control Family Study

PurposeKashin-Beck disease (KBD) is an osteoarthropathy affecting 2.5 million of 30 million residents of China's KBD-endemic regions. This study assesses the etiologic role of river water as a main source of drinking water, its impact on and interaction with KBD familial aggregation.MethodsFrom 2006–2007, we conducted a population-based case-control study of familial KBD in Linyou County, Shaanxi Province, China. Study subjects included 212 case families (1,951 individuals) and 212 control families (1,897 individuals). Using conditional logistic regression to analyze case-control data and second-order generalized estimating equation (GEE2) to examine family data, we adjusted for age and gender in all marginal regression analyses.ResultsThe odds ratio (OR) for river water intake's association with KBD was 5.97 (95% confidence interval [CI]), 3.32–10.72). Compared with relatives of controls, proband relatives had a higher risk of disease, with a conditional OR = 2.35 (95% CI, 1.05–5.24). When river water was controlled in the analyses, association parameters among first- and second-degree relatives were no longer statistically significant.ConclusionCollective river water intake among relatives was likely and predominantly responsible for familial KBD aggregation in southwestern China.