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Technical Notes 2012

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 web tables, 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 web tables, the full questionnaire may be viewed online.

For the majority of survey items, the results are displayed by sex, race, age, education, and household income. For the statewide and regional tables, disability status, veteran status and Hispanic origin are also displayed as demographic groups. Results are also posted separately by gender, by race (white and African American), and by selected risk factors (defined below).

For 2012, a total of 10 counties were over-sampled. Survey results based on the totals for each of these counties may be viewed in the table-set, NC County and AHEC Regions.

The BRFSS Survey Methodology

The 2012 BRFSS Survey carries forward the new weighting and sampling methodology initiated in 2011. For a detailed description of the new methodology see the North Carolina BRFSS 2011 Annual Technical Notes. In 2011, BRFSS results were based on a new weighting methodology that incorporates supplementary state population information (in addition to age, race, sex and ethnicity) by phone source*, education level, marital status and renter/owner status. The effect of adding these new control variables to the weighting procedure helps reduce bias in BRFSS estimates and helps enhance the generalizability of the results to the statewide population.

In addition to changes in the weighting methodology, cell phone interviews were also added to the survey in 2011. The inclusion of cell phone interviews has helped to improve BRFSS coverage of young adults and Hispanics. In the 2012 North Carolina BRFSS Survey, there were 10,497 landline respondents and 1,053 cell phone respondents; their weighted percentages were 74.8 percent and 25.2 percent, respectively.

Interpreting Results

For several years the CDC BRFSS program has suppressed prevalence estimates which did not meet minimal criteria for statistical reliability based on sample size and the width of the confidence intervals. To better meet our goal of providing high quality health information for better informed decisions and effective health policies, the SCHS has adopted this practice for our BRFSS web tables.

In our 2012 tables, we suppress prevalence estimates when any of the following criteria are met:

  1. There are fewer than 10 respondents in the numerator (i.e. the number of respondents associated with the response categories, e.g. "Yes-No").
  2. There are fewer than 50 respondents in the denominator (i.e. the total number of respondents to a question).
  3. The width of the confidence interval for the prevalence estimate is greater than 20.
  4. Cases where a table cell estimate has a relative standard error of greater than 30 percent. The relative standard error is a measure of a statistical estimate's reliability obtained by dividing the standard error by the estimate; then multiplied by 100 to be expressed as a percentage.

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 table title.

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 the national BRFSS website.

Risk Factors and Calculated Variables Presented in the 2012 BRFSS Results

Disability Status

(See the BRFSS 2011 Annual Technical Notes regarding the change in the definition for disability status.)

Yes: Respondents who reported being limited due to physical, mental or emotional problems or requiring the need for special equipment. Both elements were obtained from the two disability Core questions, sponsored by the Centers for Disease Control and Prevention (CDC).

No: Respondents who reported NOT being limited due to physical, mental or emotional problems AND NOT requiring the need for special equipment.

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.

Health Insurance Coverage - Age Under 65

Yes: All respondents less than age 65 who answered YES to the Core question on having any kind of health (HLTHPLN1). Respondents with missing age were excluded.
No: All respondents less than age 65 who answered NO to the Core question on having any kind of health (HLTHPLN1). Respondents with missing age were excluded.

Health Insurance Coverage for Those Employed for Wages (Age under 65)

Yes: All respondents less than age 65 who answered YES to the Core question on having any kind of health (HLTHPLN1), and answered “yes” to being employed for wages. Respondents with missing age were excluded.
No: All respondents less than age 65 who answered YES to the Core question on having any kind of health (HLTHPLN1), and answered something OTHER then “yes” to being employed for wages. Respondents with missing age were excluded.

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.

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, the results might understate the true level of health 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. Respondents might underreport health risk behaviors, especially those that are illegal or socially unacceptable. A third limitation is that these data are cross-sectional, collected in a single point in time. As a result, causality cannot be inferred from BRFSS survey results. All that can be determined is the likelihood of an association of between two or more variables, such as the association between smoking and cardiovascular disease – these results do not permit one to say that smoking "causes" heart disease.

Non-response is another limitation. Non-response to telephone and paper surveys has become an increasing problem for public health surveillance. In 2012, North Carolina’s non-response rate was 59.5 percent.† This means that out of all eligible survey participants, we "lost" almost 60 percent due to non-response. Non-responders may answer questions differently than responders. As a result, non-response poses a potential threat to the validity of the survey. Readers should carefully consider the non-response rates when assessing the results from any survey.

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 reduce the potential for bias.

 

*Phone source includes landline only, landline and cell, and cell-only.

†Response rates for the BRFSS are calculated using standards set by the American Association of Public Opinion Research (AAPOR) Response Rate Formula #4. The response rate is the number of respondents who completed the survey as a proportion of all eligible and likely-eligible persons. In 2012, North Carolina’s combined landline and cell phone AAPOR response rate was 40.5 percent. The non-response rate would be: 100 – 40.5.

Return to 2012 BRFSS Annual Results Table of Contents