Measuring Health Behaviors and Landline Telephones: Potential Coverage Bias in a Low-Income, Rural Population

OBJECTIVES: Population-based landline telephone surveys are potentially biased due to inclusion of only people with landline telephones. This article examined the degree of telephone coverage bias in a low-income population. METHODS: The Charles County Cancer Survey (CCCS) was conducted to evaluate cancer screening practices and risk behaviors among low-income, rural residents of Charles County, Maryland. We conducted face-to-face interviews with 502 residents aged 18 years and older. We compared the prevalence of health behaviors and cancer screening tests for those with and without landline telephones. We calculated the difference between whole sample estimates and estimates for only those respondents with landline telephones to quantify the magnitude of telephone coverage bias. RESULTS: Of 499 respondents who gave information on telephone use, 80 (16%) did not have landline telephones. We found differences between those with and without landline telephones for race/ethnicity, health-care access, insurance coverage, and several types of cancer screening. The absolute coverage bias ranged up to 6.5 percentage points. Simulation scenarios showed the magnitude of telephone coverage bias decreases as the percent of the population with landline telephone coverage increases, and as landline telephone coverage increases, the estimates from a landline telephone survey would approximate the estimates from a face-to-face survey. CONCLUSIONS: Our findings highlighted the need for targeted face-to-face surveys to supplement telephone surveys to more fully characterize hard-to-reach subpopulations. Our findings also indicated that landline telephone-based surveys continue to offer a cost-effective method for conducting large-scale population studies in support of policy and public health decision-making.