Impact of institution size, staffing patterns, and infection control practices on communicable disease outbreaks in New York State nursing homes.

Institutional risk factors associated with the occurrence of nosocomial respiratory or gastrointestinal disease outbreaks in 1992 were examined in a case-cohort study of New York State nursing homes conducted in 1993. Facility size, staffing patterns, and employee sick leave policies were the principal effects found in an unconditional logistic regression model. The risk of having respiratory or gastrointestinal disease outbreaks was greater in larger nursing homes (adjusted risk ratio (RR) = 1.71 for each 100-bed increase in size, 95% confidence interval (CI) 1.20-2.42), for nursing homes with a single nursing unit (adjusted RR = 3.93, 95% CI 0.98-15.71), or those with multiple nursing units with shared staff (adjusted RR = 2.51, 95% CI 1.07-5.89). The risk was less for nursing homes with paid employee sick leave policies (adjusted RR = 0.38, 95% CI 0.15-0.99). Other potential risk factors examined in this study, such as the ratio of beds per unit, type of sponsorship, daily review of laboratory test results, and the proportion of private beds and patient-to-staff ratio, were not significantly associated with the risk of disease outbreaks. The results of this study have direct implications for control of nosocomial disease outbreaks in nursing homes.