Diabetes Prevention and Control
Behavioral Risk Factor Surveillance System Description
The Behavioral Risk Factor Surveillance System (BRFSS) is conducted by the Alaska Division of Public Health in cooperation with the National Centers for Disease Control and Prevention (CDC). It is a monthly telephone survey that utilizes a standard protocol and interviewing methods developed by the CDC.
The BRFSS instrument is a standardized questionnaire, which consists of three sections:
- The core (which includes demographics)
- A set of optional modules and
- State specific questions.
The questionnaire covers such topics as Health Status, Health Care Access, Nutrition, Physical Activity, Diabetes, Tobacco Use (including Smokeless Tobacco), Alcohol Use, Demographics, Women's Health, Injury Prevention, and HIV/AIDS Awareness.
Each month over 200 Alaska residents age 18 and older are interviewed over the telephone, to reach an annual sample size of 2,500 (500 per region). The data are collected from January through December, for each year.
Participation is random, anonymous and confidential. Respondents are randomly selected from among the adult members of the household. Only those living in households are surveyed. Those living in institutions (i.e., nursing homes, dormitories) are not surveyed.
A stratified random sampling design is used on the Alaska BRFSS. The Alaska sample is stratified into five regions based on common demographics. An equal number of interviews are conducted in each region, which purposely over-samples the non-urban areas of Alaska.
The data are weighted or adjusted to compensate for the overrepresentation or under-representation of persons in various subgroups. The data are further weighted to adjust the distribution of the sample data so that it reflects the total population of the sampled area.
The data weighting process does not take into account differences in the age distribution in Alaska compared to other populations. The data presented are either in the crude form, defined as the “observed rate”, or are age-adjusted to the U.S. 2000 census standard age distribution. Age-adjustment is the application of observed age-specific rates to a standard age distribution to eliminate differences in crude rates of populations of interest that result from differences in the populations’ age distributions. The age-adjustment process is important when comparing two or more populations at one point in time, or when comparing one population at two points in time. When the data are presented individually, and not in a comparison, it may be more appropriate to use the crude data. These data more accurately represent the number of people in the state of Alaska.
The BRFSS uses telephone interviewing for several reasons. Telephone interviews are faster and less expensive than face-to-face interviews. Calls are made from one central location (Juneau) and are monitored for quality control.
The one main limitation of any telephone survey is that those people without phones cannot be reached and are not represented. In Alaska, about 97% of households have phones (about 95% of all U.S. households have phones). The percentage of households with a telephone varies by region in Alaska. In general, persons of low socioeconomic status are less likely than persons of higher socioeconomic status to have phones and are undersampled. However, national BRFSS results correspond well with findings from other surveys conducted in person.
With surveys based on self-reported information, there is a potential for bias in interpreting results. Survey response rates may also affect the potential for bias in the data.
The reliability of a prevalence estimate depends on the actual, unweighted number of respondents in a category or demographic subgroup (not a weighted number). Interpreting and reporting weighted numbers that are based on a small, unweighted number of respondents can be misleading. The degree of precision increases if the sample size is larger and decreases if the sample size is smaller. Prevalence estimates are not usually reported for those categories in which there were less than 50 respondents and are rounded to the nearest whole percent when the denominator is less than 500.
For more information, please see the Alaska BRFSS website, or contact the Alaska BRFSS Coordinator, Rebecca W. Topol, SM, telephone: (907) 465-8540, email: Rebecca.Topol@alaska.gov
State of Alaska, Department of Health and Social Services, Alaska Behavioral Risk Factor Surveillance System Program. Health Risks in Alaska Among Adults
. Alaska Behavioral Risk Factor Survey, 2000/2001 Annual Report. 2001.
BRFSS Home Page