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The Impact of Wireless Substitution on Random-Digit-Dial Health Surveys. Stephen Blumberg Julian Luke. Centers for Disease Control and Prevention National Center for Health Statistics. Goals of this Presentation.
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The Impact of Wireless Substitution on Random-Digit-Dial Health Surveys Stephen Blumberg Julian Luke Centers for Disease Control and Prevention National Center for Health Statistics
Goals of this Presentation • Describe the telephone coverage of the U.S. household population, with a particular focus on persons who have substituted wireless telephones for landline telephones • Examine the potential bias that may result when health surveys exclude households without landline telephones
National Health Interview Survey • In-person survey of the civilian noninstitutionalized U.S. population • Annual household-level response rates are very high (86-92%) • Includes questions on residential telephone numbers to permit recontact of participants • 2003: Added questions on working cellular telephones
Identifying Wireless-Only Persons • “What is your family’s telephone number?” • “Does anyone in your family have a working cellular telephone? • “Is ###-###-#### the telephone number for one of the cellular phones?” • “Is there at least one telephone inside your home that is currently working and is not a cellular telephone?”
Prevalence of Adults and ChildrenBy Household Telephone Status
Prevalence of Adults and ChildrenBy Household Telephone Status • During the second half of 2005 • 77% of nonlandline households had wireless telephones • 17.1 million adults (18+) were wireless-only • 5.7 million children (<18) were wireless-only • Growth since 2003 • 23% compound growth in the prevalence of wireless-only adults EVERY SIX MONTHS • 19% compound growth in the prevalence of wireless-only children EVERY SIX MONTHS • But a jump of 33% in the past six months!!
Prevalence of Wireless-Only Adultsby Home Ownership Status 19.6% of adults renting their home 8.5% of adults with other arrangements 3.9% of adults owning or buying home
Prevalence of Wireless-Only Adultsby Household Structure 34.0% of adults living with roommates 12.4% of adults living alone 7.1% of adults living with children 6.0% of adults living with related adults
Prevalence of Wireless-Only Adultsby Age 17.8% of 18-24 10.7% of 25-44 3.7% of 45-64 1.2% of 65+
Prevalence of Wireless-Only Adultsby Sex 8.6% of men 7.0% of women
Prevalence of Wireless-Only Adultsby Race/Ethnicity 11.3% of Hispanic adults 8.6% of Black nonHispanic adults 7.0% of White nonHispanic adults
Prevalence of Wireless-Only Adultsby Household Poverty Status 14.3% of adults in poverty 12.8% of adults near poverty 7.0% of higher income adults
Prevalence of Wireless-Only Adultsby Highest Completed Education 9.5% of adults with some college 8.8% of adults with less than HS 7.7% of high school graduates 6.3% of college graduates
Prevalence of Wireless-Only Adultsby Employment Status Last Week 15.5% of adults going to school 9.2% of adults working at a job 6.2% of adults keeping house 3.8% of other adults (incl. unemployed)
Prevalence of Wireless-Only Adults byMetropolitan Statistical Area Status 8.8% of adults in MSAs 5.1% of adults not in MSAs
Prevalence of Wireless-Only Adultsby Geographic Region 9.6% in South 8.8% in Midwest 6.3% in West 4.7% in Northeast
Multivariate Analyses: SEARCH • Sequential series of chi-square analyses to identify the predictor variables that yield the greatest differences in the distributions of the dependent variable • Predicting “landline absent” vs. “landline present”
Prevalence of Adults Living in Households Without Landlines, 2005
Coverage Bias • Two factors determine the degree of coverage bias due to telephone ownership in a telephone survey: • The percentage of persons without landline telephones in the population of interest • The magnitude of the difference between persons with and without landline telephones on the variable of interest
Health-related behaviors 5+ alcoholic drinks in one day (past year) Smoking (current) Leisure-time physical activity (regularly) Health status Excellent or very good health status Serious psychological distress (past 30 days) Obesity Asthma episode (past year) Diabetes (ever diagnosed) Health care service use Has a usual place to go for medical care Received influenza vaccine (past year) Received pneumococcal vaccine (ever) Tested for HIV (ever) Financial barrier to needed care (past year) Uninsured (current) Health Characteristics Examined For these 14 estimates, weighted data from January – December 2005 were produced by the NHIS Early Release Program.
Percent of Adults with Various Health Characteristics, by Phone Status
Percent of Adults with Various Health Characteristics, by Phone Status
Potential Bias in Prevalence Estimatesfor All Adults These were the only differences (of the 14 measures considered) that are greater than one percentage point.
Wireless-Only: A Summary • In late 2005, 10.4% of all households did not have a landline telephone and could not be reached by random-digit-dial telephone surveys • Rate is growing by approximately one percentage point every 6 months • Noncoverage of wireless-only households in telephone surveys can lead to bias, but the magnitude of that bias is still small
American Journal of Public Health,May 2006, vol. 96, pp. 926-931
For More Information… • Stephen Blumberg Centers for Disease Control and Prevention National Center for Health Statistics 3311 Toledo Road, Room 2112 Hyattsville, Maryland 20782 • sblumberg@cdc.gov