An Overview of the North Carolina Behavioral Risk Factor Surveillance System (BRFSS)

Presentation to the

State Health Director's Conference

January 23, 2014

State Center for Health StatisticsDivision of Pubic HealthNC Dept. of Health & Human Services

Presentation Outline

How the survey is done Questionnaire development Sampling Data Collection Weighting

Future developments Demonstrate how to access results Q&A

State Center for Health StatisticsDivision of Pubic HealthNC Dept. of Health & Human Services

Timeline for 2014 BRFSSExternal review of proposed new/revised questions2012

2013 State Coordinators vote on proposed questions

CDC field tests questionnaire

CDC Core & Optional Modules checked and finalized

State-added questions reviewed and finalized

CATI coding developed and checked

Interviewers trained

2014 Conduct interviews January through December

CDC sends final weighted data to NC

SCHS reviews data and produce web tables

2015

BRFSS QUESTIONNAIRE

Questionnaire Organization

Each years survey is divided into three main parts

CDCCore

Questions

CDCOptionalModules

State-Added

Questions

Mandated by CDC;must ask all questions exactly as written

States choose whichmodules they willadminister; must askall questions exactlyas written

Developed by eachstate’s coordinator

The Core The CDC Division of Behavioral Surveillance (DBS) works with

other CDC programs to develop questions for the core & optional modules

Proposed questions undergo two rounds of cognitive testing State Coordinators have input via

Participation in State Working Group Participation as external reviewer for proposed questions Vote on proposed questions taken at Annual Conference

Questions rotate in & out of core on a fixed schedule Just adopted a new 5-year plan for the core

CDC Optional Modules

Process for developing optional modules is similar to the core

CDC programs pay DSB for space on the BRFSS

So the selection of optional modules available varies each year

State-Added Questions

May include Questions from other surveys, including questions

on CDC Optional Modules Questions written by state staff

Each state has a process for soliciting proposed questions

Survey time is a very scarce resource When telephone interviews run past 15 to

20 minutes, Break-offs increase Data quality suffers as people say whatever

comes to mind so you’ll leave them alone! Some cell phone respondents are more

sensitive to length because they pay by the minute

Pew Research Center successfully does 20 minute cell phone interviews

The 2013 NC BRFSS interview averaged 29 minutes 17 minutes of that is take up by Core questions and an

expanded Optional Module on Health Care Access “Core creep” – expansion of the length of the core – is a

major issue with state coordinators We have been trying to cut down on state-added

and CDC Optional Modules to shorten the interview

SAMPLING

Random Digit Dialing (RDD) Surveys 4 digit numbers are generated at random

within each combination of area code and phone exchange within a geographic area

Resulting numbers are screened to identify non-working numbers

Results in a random sample of telephone numbers for a given geographic region

BRFSS uses a Dual-Frame RDD Sample Landline Frame

Numbers generated within area code/exchange combinations for landline telephones

Telco companies share more information regarding these numbers Most importantly where the phone is located

Cell Phone Frame Numbers generated within area code/phone

exchange combinations for cell phones Cell phone companies share little information

about these numbers Little information on where owner of phone lives until

they are interviewed

Increase in “Cell Phone Only” (Wireless) Households Roughly 38% of adults as of

the end of 2013. These folks are:

Younger More are minorities Less affluent Have some significantly

different health conditions & behaviors

Must sample this population to avoid biased estimates

DATA COLLECTION

“BRFSS is a process, not a project” Survey runs throughout calendar year

Each month we receive separate landline and cell phone samples (~8,000 phone numbers total)

To complete each month’s “study” Each landline number is called up to 15 times Each cell phone number is called up to 8 times

We call seven days a week around 330 days every year

More difficult to reach cell phone respondents In the landline sample

Get one completed interview every 1.4 hours of interview time

Perform 38 dialings per completed interview 4,600 sample records yield ~900 completed interviews

Cell Get one completed interview for every 1.7 hours Perform 97 dialings per completed interview 3,200 sample records yield ~100 completed interviews

Bottom Line: We have to call many, many more cell phone numbers before finding someone who will complete the interview

WEIGHTING

Why Weight?

We weight survey data to make our sample better match the population

Some observations “get counted” more than others

BRFSS Weighting Systems

The old BRFSS system used gender, age, race/ethnicity, & region within state to adjust the final results.

The new rake weights adds adjustment by education level, marital status, renter/owner status & phone source (landline vs. cell phone)

The new “raked” weights should improve the representativeness of the sample, particularly regarding socioeconomic status

The new weights, together with adding cell-phone interviews, produces different estimates for some health indicators

Percent of Adults Who Are Current Smokers, 2010

19.78

24.12 25.26

0

5

10

15

20

25

30

Landline only, old weight Landline only, raked weight Landline & cell, raked weight

Sample & Weight Used

Percentage

Some estimates change a lot:

Estimate increases by ~ 5.5 percent

Binge Drinking

11 11.16

14.28

0

2

4

6

8

10

12

14

16

Landline only, old weight Landline only, raked weight Landline & cell, raked weight

Sample & Weigh Used

Per

cen

tag

e

Estimate increases by ~ 3.3 percent

Some estimates change very little:

Estimate increases by ~ 1.0 percent

Percentage of Adults Diagnosed with Diabetes, 2010

9.77

11.6210.74

0

2

4

6

8

10

12

14

Landline only, old weight Landline only, raked weight Landline & cell, raked weight

Sample & Weight Used

Per

cen

tag

e

Percentage of Adults Getting Recommended Amout of Physical Activity, 2009

46.4143.98 45.46

0

510

15

2025

30

35

4045

50

Landline only, old weight Landline only, raked weight Landline & cell, raked weight

Sample & Weight Used

Percentage

Estimate increases by ~ 0.9 percent

FUTURE DEVELOPMENTS

Change to Geographic Strata

Beginning in 2014, geographic strata will be based on Area Health Education Center regions Able to stratify both landline and cell phone

samples for these area

We will produce estimates for State as a whole Eastern, Piedmont & Western Carolina AHECS Counties when possible

At least 500 completed interviews in the sample

HOW TO ACCESS RESULTS

Data for a calendar year are combined and analyzed

Results for state and sub-regions are posted to SCHS Web page Main SCHS Web Page

http://www.schs.state.nc.us/ NC BRFSS Web Page

http://www.schs.state.nc.us/units/stat/brfss/

Contact Information: James Cassell

Head of Survey Operations & BRFSS CoordinatorState Center for Health StatisticsNorth Carolina Division of Public Health2422 Mail Service CenterRaleigh, NC 27699-2422

Voice: 919-855-4485Fax: 919-715-7899Email: james.cassell@dhhs.nc.gov

NC BRFSS Web Page http://www.schs.state.nc.us/units/stat/brfss/

State Center for Health StatisticsDivision of Pubic HealthNC Dept. of Health & Human Services