Adult Asthma Module: Technical information
BRFSS Core Questionnaire
In each area where interviews are conducted, respondents are randomly selected from noninstitutionalized civilian adults (18 years of age or older) living in households with a telephone (BRFSS User's Guide [PDF - 1.7 MB]). Asthma prevalence data are produced from the responses to two asthma questions on the 2007 BRFSS Core Questionnaire.
Lifetime asthma: Question number 9.1
“Have you ever been told by a doctor, nurse, or other health professional that you had asthma?” (Variable name: ASTHMA2)
The calculated variable _LTASTHMA (based on question 9.1) from the public use file was used when creating the tables.
Current asthma: Question number 9.2
If the response to 9.1 was “Yes,” then question 9.2 was asked: “Do you still have asthma?” (Variable name: ASTHNOW)
Adult module tables include only respondents who answered “yes” to both the lifetime and the current asthma question.
Module tables are based on data from the following questions:
|Adult Asthma Module Questions, Variable Names and Codes Used in Module Tables |
|1. How old were you when you were first told by a doctor, nurse, or other health professional that you had asthma? Table Label: Age at diagnosis (onset)|
Grouped into Child (<18) and Adult (18+)
|ASTHMAGE||11 - 95 96 = 96 and older] 97 = 10 or younger|
|2. During the past 12 months, have you had an episode of asthma or an asthma attack? Table Label: Attack|
Did not have attack v. Had an attack
|ASATTACK||1 = yes 2 = no|
|3. During the past 12 months, how many times did you visit an emergency room or urgent care center because of your asthma? Table Label: Emergency Department Visits|
Grouped into No Visit; Any Visit (one, two, or more)
|ASERVIST||_ _ Number of visits 87 = 87 or more 88 None|
|4. During the past 12 months, how many times did you see a doctor, nurse, or other health professional for urgent treatment of worsening asthma symptoms? Table Label: Urgent Doctor Visits|
Grouped into No Visit; Any Visit (one, two, or more)
|ASDRVIST||_ _ Number of visits 87 = 87 or more 88 None|
|5. During the past 12 months, how many times did you see a doctor, nurse or other health professional for a routine checkup for your asthma? Table Label: Routine Doctor Visits|
Grouped into No Visit; Any Visit (one, two, three, or more)
|ASRCHKUP||_ _ Number of visits 87 = 87 or more 88 None|
|6. During the past 12 months, how many days were you unable to work or carry out your usual activities because of your asthma? Table Label: Activity Limitation|
Grouped into No Days; Any Days (1–10; >10)
|ASACTLIM||_ _ _ Number of days 888 None|
|7. Symptoms of asthma include cough, wheezing, shortness of breath, chest tightness, and phlegm production when you don’t have a cold or respiratory infection. During the past 30 days, how often did you have any symptoms of asthma? Table Label: Days with Symptoms|
Grouped into No Days; Any Days (1: < once/week; 2–3: once or more/week, 4–5: every day)
|ASYMPTOM||8 Not at any time [Go to Q9] 1 Less than once a week 2 Once or twice a week 3 More than 2 times a week, but not every day 4 Every day, but not all the time 5 Every day, all the time|
|8. During the past 30 days, how many days did symptoms of asthma make it difficult for you to stay asleep? Table Label: Days with Sleep Disturbance|
Grouped into No Days; Any Days (1–2, 3–10, >10)
|ASNOSLEP||8 None 1 One or two 2 Three to four 3 Five 4 Six to ten 5 More than ten|
|9. During the past 30 days, how many days did you take a prescription asthma medication to PREVENT an asthma attack from occurring? (2005 and later) Table Label: Preventive Medication (30 days)|
Grouped into No Days; Any Days (1–14, 15–24, 25–30)
|ASTHMED2 (2005-2006) ASTHMED3 (2007)||8 Never 1 1 to 14 days 2 15 to 24 days 3 25 to 30 days|
|10. During the past 30 days, how often did you use a prescription asthma inhaler DURING AN ASTHMA ATTACK to stop it? (2005 and later) Table Label: Rescue Inhaler (30 days)|
Grouped into No Days; Any Days (1–4, 5–14, 15–59, 60+)
|ASINHALR||8 Never 1 One to four 2 Five to fourteen 3 Fifteen to twenty-nine 4 Thirty to fifty-nine 5 Sixty to ninety-nine 6 More than 100 times|
|During the past 30 days how often did you take asthma medication that was prescribed or given to you by a doctor? This includes using an inhaler. (2001–2004) Table Label: Medication Status 2001– 2004|
Grouped into: None, Any (less than once a week; >=1 time a week, but not daily; once every day; two or more times every day)Table Label: Medication Status 2005 and later
“Any” if Preventive Medication = 1, 2, 3 or Rescue Medication = 1, 2, 3, 4, 5, 6; “None” if Preventive Medication = 8 and Rescue Medication = 8
|ASTHMEDS||8 Didn’t take any 1 Less than once a week 2 Once or twice a week 3 More than 2 times a week, but not every day 4 Once every day 5 2 or more times every day|
Survey Design and Sample Weights
The survey design is described in the technical pages document for each year, for example, "2007 Overview" at http://www.cdc.gov/brfss/technical_infodata/surveydata/2007.htm. Sample weights are assigned, according to BRFSS methodology, to the variable _FINALWT as described in the BRFSS Weighting Formula.
The BRFSS Survey Data files for 2002 to 2007 were used to calculate estimates for states that included the adult asthma module in their BRFSS survey. States for each year are indicated below:
|California, Delaware, DC, Idaho, Iowa, Louisiana, Massachusetts, Michigan, New Hampshire, New Jersey, New Mexico, North Carolina, Ohio, Oklahoma, Rhode Island, Texas, Utah, Wisconsin, Virgin Islands|
|Connecticut, Delaware, District of Columbia, Georgia, Hawaii, Indiana, Iowa, Maryland, Michigan, Minnesota, New Hampshire, New Jersey, New Mexico, Oklahoma, Texas, Utah, Vermont, Virginia, Wisconsin|
|Alaska, Arizona, California, Georgia, Hawaii, Idaho, Iowa, Kentucky, Louisiana, Maryland, Michigan, Minnesota, Mississippi, Montana, New Hampshire, New Jersey, New York, Ohio, Oklahoma, Pennsylvania, Puerto Rico, Texas, Utah, Vermont, Virginia, Wisconsin|
|Arizona, Colorado, Connecticut, Delaware, Georgia, Idaho, Indiana, Iowa, Maine, Missouri, Montana, New Jersey, New York, Ohio, Pennsylvania, Rhode Island, Texas, Utah, Vermont, Virginia, West Virginia, Wisconsin|
|Idaho, Kentucky, Louisiana, Mississippi, Nevada, New Jersey, New Mexico, North Carolina, Ohio, Oklahoma, Puerto Rico, Rhode Island, Utah, West Virginia|
|Arizona, Colorado*, Idaho, Mississippi, New Jersey* , North Carolina, Oklahoma, Pennsylvania, Puerto Rico, Virginia|
* Used a Dual Questionnaire (split sample).
Percent and standard error estimates were calculated using the SAS 9.1 PROC SURVEYFREQ procedure to account for survey data from complex sample designs. The BRFSS employs a complex stratified sample design. Therefore, an analysis that ignored the complex design clustering and stratification and the sample weights (for example the SAS PROC FREQ procedure) would result in biased estimators.
Only respondents with values of the variables as described in the table above are included in each table. Responses of “don’t know/not sure,” “refused,” or missing values were excluded.
In the original data sets, those respondents answering “Not at any time” to the question “days of asthma symptoms in the past 30 days” had missing values in the question “days of sleep disturbance in the past 30 days” because of a skip pattern in the interview sequence. Therefore, those answering “Not at any time” to the question days of asthma symptoms in 30 days were recoded to “None” for the question “days of sleep disturbance in the past 30 days.”
For “days of activity limitation in 12 months,” the respondents with a response code of “88” days were excluded. Previous investigations indicated that an “88”represented a coding error resulting from the numerical similarity with the code for no days (888).
In the 2005 data, Delaware data included an unusually large percentage of “Don’t Know/Not Sure” for the questions “age of asthma onset” and “use of rescue inhaler in 30 days.” After BRFSS staff in Delaware was consulted, the data were revised to correct a coding error.
Sample weights for states implementing split sample designs have been adjusted to account for the use of dual questionnaires (Colorado and New Jersey in 2007).
The first table in each file is a summary table with data from all the states that implemented the adult module. It excludes any U.S. territories that implemented the module. Individual tables for each state and each territory that conducted the adult module follow the summary table.
The tables examine interrelationships between multiple asthma-control indicators (rows) and a primary variable (columns). For the years 2002 to 2004, separate tables are provided for three primary variables (Sex, Age at Diagnosis, and Medication Status). Each table includes the following indicators: Age at Diagnosis (if not the primary variable), Medication Status (if not the primary variable), Attack, Emergency Department Visits, Urgent Doctor Visits, Routine Doctor Visits, Activity Limitations, Days with Symptoms, and Days with Sleep Disturbance. Beginning with 2005, tables are provided for five primary variables (Sex, Age at Diagnosis, Medication Status, Rescue Inhaler, and Preventive Medication). Each primary variable table includes the following indicators: Age at Diagnosis (if not the primary variable), Preventive Medication (if not the primary variable), Rescue Inhaler (if not the primary variable), Attack, Emergency Department Visits, Urgent Doctor Visits, Routine Doctor Visits, Activity Limitations, Days with Symptoms, and Days with Sleep Disturbance.
The relationship between each indicator variable (rows) and the three primary categorical variables (2002–2004) or the five primary categorical variables (2005 and later) were examined. Indicator variables were categorized in two different ways. First, each indicator was dichotomized to represent any event or no event (visit, days, attack, medication use). Second, the “Any” category was grouped into several sub-categories by collapsing question response categories as shown in the table above.
For each indicator variable for each of the three primary categorical variables (2002–2004) or five primary categorical variables (years since 2005) the proportion estimates and variance estimates were calculated. The Wald test was used to determine if there was a significant relationship between each indicator variable and the primary categorical variables. Tests were done separately for the dichotomized version of the indicator and for the multiple category version of the indicator. The resulting P-values are reported in each table.
Small Sample Size
When sample sizes in cells are less than 50, as they are in some of the state/territory tables, the standard error may be large relative to the estimate value, leading to a wide 95% confidence interval. Caution should be used in interpreting such “imprecise” estimates.