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Behavioral Risk Factor Surveillance System (BRFSS)
Several changes have been made to the 2008 NC BRFSS tables. First, the rule for interpreting results (found in the footnote of each table) based on small numbers has been changed. In previous years, the rule stated: "Use caution in interpreting percentages with a numerator of less than 20." The rule now states, "Use caution in interpreting cell sizes less than 50." The rule was changed to comply with that found on the CDC (Centers for Disease Control and Prevention) BRFSS web site. 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, and gives consideration to 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. We do not suppress these results, but the reader should be aware when this occurs and should view these results as NOT reliable. An example of this can be found with the 2008 race/sex subgroup tables for African American females on the topic of Adult Asthma History. For the question, "During the past 12 months, have you had an episode of asthma or an asthma attack," a total of 159 respondents answered the question and 78 of these respondents reported "yes." Here, the number in the denominator is 159 and the number in the numerator is 78, yielding a weighted percentage of 40.6%; however, the associated confidence interval ranges from 30.0% to 52.2%. The half-width for this confidence interval is 11.1 percent. Clearly, these results have a large degree of statistical error and should not be relied upon.
A second change occurred with respect to the suppression of results. If there were fewer than 80 respondents who answered the question, the results are limited to the total sample. This was mostly true of county-level tables because of their relatively small sample sizes. For example, there were only 33 respondents in Buncombe County with current asthma; thus, for questions pertaining to current asthma, only the top row of data is displayed. There was one exception to the "less than 80 rule" that applied only to the race/sex tables. If there were less than 140 respondents who answered the question, the results are limited to the total. This is because age, and its seven age groups, is the first demographic breakout to appear in these tables. For example, there were only 107 African American females who answered the question: During the past 30 days, how many days did symptoms of asthma make it difficult for you to stay asleep? If these 107 respondents were distributed across seven age groups, many categories would have fewer than 10 respondents; thus, age, in this case, would not provide reliable results.
Our policy is to show the results for at least the total row for all questions, even those with fewer than 50 respondents, but it is up to the reader to exercise caution when small numbers appear in the results.
A third change occurred with respect to age-dependent topics, such as prostate cancer screening, which was asked only of men 40 years or older. Beginning this year, the age ranges are included in the title, obviating the need for footnotes. In addition to this change, the statewide results are also featured in all of the race/sex tables.
Weighted BRFSS data are used in all calculations. 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 the majority of tables, the results are displayed by sex, race, age groups, education levels, household income, disability status, and veteran status. For the statewide and regional tables with large sample sizes, Hispanic origin is displayed as a demographic group. The results are also available for 23 of the state's largest counties, race-sex subgroups, and by risk factors.
All questions from the survey are not presented in the following tables; however, the full questionnaire may be viewed online. Whenever possible, the exact wording for each question is used as a title, however due to space limitations, the titles may not include some introductory remarks and explanations for some questions. For more technical information about BRFSS, please visit national BRFSS web site.
Risk Factors and Calculated Variables Presented in the 2008 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 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.
Have had a mammogram within the past 2 years (Age 40+)
Yes: Females age 40 and older who reported ever having a mammogram and reported having their last mammogram within the past 2 years (less than 2 years ago).
No: Females age 40 and older who reported ever having a mammogram and reported having their last mammogram 2 or more years ago.
Have had a mammogram within the past 2 years and a clinical breast exam within a year (Age 40+)
Yes: Females age 40 and older who reported having their last mammogram within the past 2 years (less than 2 years ago) and their last clinical breast exam with the past year (less than 12 months ago).
No: Females age 40 and older who reported never having a mammogram or never having a clinical breast exam, or reported having their last mammogram 2 or more years ago or their last clinical breast exam more than 1 year ago.
Women age 18+ who have had a Pap Smear in the last 3 years
Yes: Females age 18 and older who reported ever having a Pap test and reported having their last Pap test within the past 3 years (less than 3 years ago).
No: Females age 18 and older who reported never having a Pap test, or reported having their last Pap test 3 or more years ago.
Note: Women who reported having a hysterectomy were not included in these calculations.
Disability Status
Yes: Respondents who report 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
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.
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.
Additionally, the widespread use of cellular phones has also impacted the BRFSS telephone survey. As more households across the country abandon landline phones and become "cell phone only" households, the CDC-BRFSS is devising plans to address this change. In 2009, the North Carolina BRFSS survey is conducting a cell phone pilot study. Beginning in 2010, cell-phone-only households will be included as a standard component of the annual BRFSS data collection process.
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.
