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Technical Notes 2009

Behavioral Risk Factor Surveillance System (BRFSS)

Detailed data tables for NC BRFSS survey items are posted by the SCHS on an annual basis. The exact wording for each question is used as a title for the majority of the webtables, however due to space limitations the titles may not include some introductory remarks and explanations for some questions. Although not all survey questions are presented in the webtables, the full questionnaire may be viewed online.

For the majority of survey items, the results are displayed by sex, race, age group, education level, household income, disability status, and veteran status. For the statewide and regional tables, Hispanic origin is displayed as a demographic group when sample size permits.

Results are also posted by gender, by race, by risk factors (defined below), and for 23 of the state's largest counties. However, if the total number of respondents is less than 80, the results are limited to the total sample and further subgroups are not presented. This occurred for many county-level tables because of their relatively small sample sizes. For example, only 54 respondents in Mecklenburg County have ever been told by a doctor that diabetes has affected their kidneys; thus, only the county-level estimate is displayed and further subgroups are not presented (i.e. gender, race, age, education, and income). For 2009, results by gender and race will not be posted. Decreases in funding have severely affected our overall sample size and as a result, most cell sizes in the tables by gender and race fall below the CDC recommendations.

Interpreting Results
Following guidance from the CDC, the reader should give consideration to both the sample size and the width of the confidence intervals when interpreting results. Readers should use caution in interpreting cell sizes less than 50. The cell size is either the number of respondents found in the denominator, i.e., the table column labeled, "Total Respond.," or the numerator. The cell size for the numerator is defined by the number of respondents associated with the response categories (e.g., "Yes-No"). The CDC rule is a more conservative rule than used in previous years, and also considers results based on the denominator, i.e., the total number of respondents who answered the question.

When interpreting the results, the reader should also give consideration to the width of the confidence intervals. The CDC suppresses the results if the half-width of the confidence interval is greater than 10 percent. Although the SCHS does not suppress these results, the reader should be aware when this occurs and should view these results as NOT reliable. For example, for Smoking Status, 73 of the 105 Asian respondents reported never smoking. Here, the number in the denominator is 105 and the number in the numerator is 73, yielding a weighted percentage of 61.8. Although the cell sizes are greater than 50, note that the confidence interval ranges from 48.1 to 73.8; the half-width for this confidence interval is 12.85. These results have a large degree of statistical error and are considered unreliable.

Although it is the policy of the SCHS to post results for all survey questions, including results with fewer than 50 respondents, it is up to the reader to exercise caution when small numbers appear in the results.

Some topics are age-dependent topics, such as prostate cancer screening, which was asked only of men 40 years or older. Please note age ranges for particular survey items in the web table’s footnotes or as cited in the questionnaire.

Weighted BRFSS data are used in all calculations; therefore percentages shown in web tables cannot be derived exactly from the numbers presented. BRFSS data are weighted for the probability of selection of a telephone number, the number of adults in a household, and the number of phones in a household and adjusted to reflect the demographic distribution of North Carolina's adult population (ages 18 and older).

Respondents who refused to answer or did not know the answer were excluded from most calculations in these tables. However, there are instances when "Don't know/Not sure" responses may provide valuable information and are included in the response categories.

For more technical information about BRFSS, please visit national BRFSS web site.

Risk Factors and Calculated Variables Presented in the 2009 BRFSS Results

Body Mass Index Grouping

Body mass index (BMI) is computed as weight in kilograms divided by height in meters squared:(kg/ m2). BMI is an intermediate variable used in calculating these measures:
Underweight: BMI less than 18.5, Recommended Range: BMI 18.5 to 24.9, Overweight: BMI 25.0 to 29.9, Obese: BMI greater than 29.9. and Overweight or Obese: BMI greater than 24.9.

Smoking Status

Current Smoker (every day): Respondents who have smoked at least 100 cigarettes in their lifetime and now smoke every day.
Current Smoker (some days): Respondents who have smoked at least 100 cigarettes in their lifetime and now smoke some days.
Former Smoker: Respondents who have smoked at least 100 cigarettes in their lifetime and currently do not smoke.
Never Smoked: Respondents who have not smoked at least 100 cigarettes in their lifetime.

Current Smoker

Yes: Current Smoker (every day or some days)
No: Former Smoker or Never Smoked.

Binge Drinking

No : Respondents who report they did not drink in the past 30 days, or who drank in the past 30 days but did not have five or more drinks for males or four or more drinks for females on an occasion.
Yes : Respondents who report they did drink in the past 30 days and had five or more drinks for males or four or more drinks for females on one or more occasions in the past month.

Heavy Drinking

Yes: Respondents reported having MORE than 2 drinks/day for MALES and MORE than 1 drink/day for FEMALES.
No: Respondents reported having LESS than or equal to 2 drinks/day for MALES and LESS than or equal to 1 drink/day for FEMALES.

Disability Status

Yes: Respondents who reported being limited due to physical, mental or emotional problems or using special equipment or having learning problems or considering himself or herself as having disability.
No: Respondents who reported NOT being limited due to physical, mental or emotional problems or using special equipment or having learning problems or considering himself or herself as having disability.

Strengths and Limitations of the BRFSS Survey Data

One limitation of a telephone survey is the lack of coverage of persons who live in households without a telephone. Households without a telephone are, on average, of lower income. Therefore, for many of the health risks measured, the results are likely to understate the true level of risk in the total population of adults in North Carolina. A second limitation is due to the fact that the data are self-reported by the respondents. We expect that respondents tend to underreport health risk behaviors, especially those that are illegal or socially unacceptable.

There are some significant advantages of the telephone survey methodology, including better quality control over data collection made possible by a computer-assisted-telephone-interviewing system, relatively low cost, and speed of data collection. The BRFSS methodology has been used and evaluated by the CDC and participating states since 1984. The content of the survey questions, questionnaire design, data collection procedures, interviewing techniques, and editing procedures have been carefully developed to improve data quality and lessen the potential for bias. The data collection is ongoing, and each year new annual results become available.

Surveying “Cell Phone Only” Households

The widespread use of cellular phones has also impacted the BRFSS telephone survey. Previous studies have found differences in “cell phone only” compared to landline telephone populations in demographic, economic, and health characteristics. Cell phone only samples are more likely to be male, African American, Hispanic, under the age of 34, employed, of lower income, and/or unmarried compared to landline only samples. Significant differences in health care access and behaviors also have been found. For example, “cell phone only” adults are more likely to be binge drinkers, smokers, people who engage in regular physical activities, have an unmet need for medical care due to cost, and have used preventive health care services.  However, demographic weighting adjustments greatly reduce these biases such that when data from landline telephone surveys are weighted to match population demographic characteristics, bias is similar to the margin of sampling error on the landline sample (less than 2 percentage points) for the majority of health indicators. Although greater bias (1-5%) has been found for some estimates of health care and behavioral health indicators (e.g. binge drinking, smoking, financial barriers to medical care) to specific populations (i.e. young or low-income adults), bias can be attenuated to some extent through weighting adjustments. BRFSS post-stratification adjustments include age, race, sex and ethnicity. The CDC is currently developing weights for the BRFSS data using raking methodology that will also allow for marital status and education to be included in the post-stratification weighting process. With the addition of education and marital status, these raked weights will yield a weighted sample that is more representative of the state's less educated or lower income population. Thus, the raked weights may further account for these differences between cell phone only and landline populations and aid in producing less biased estimates.

As more North Carolinians abandon landline phones and become “cell phone only,” the SCHS recognizes the importance of incorporating these households into the BRFSS survey framing scheme. In 2009, the NC BRFSS added a cell phone component to its landline survey. However, fiscal constraints make expanding surveys to include “cell-phone only” households difficult. Including a cell phone component substantially increases program expenditures given that a cell phone interview costs roughly two and a half times the cost of a landline interview. This is because it takes significantly more time (e.g. log on hours) and effort (e.g. more dialings) per interview to complete a cell phone interview compared to a landline interview. Therefore, additional funding dedicated to collecting a cell phone sample will be necessary for the NC BRFSS to survey households that are serviced only by cell phones.

Return to 2009 BRFSS Annual Results Table of Contents