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DHDS Methods

Disability and Health Data System (DHDS) contains data on two core indicators―Disability Status and Psychological Distress Status. Data also are available for disability-associated health care expenditures.

Indicator definitions and the methodology for calculating estimates are specific to Disability and Health Data System (DHDS) and might not be applicable outside of this system. Therefore, estimates in DHDS may not match those reported in other Centers for Disease Control and Prevention (CDC) data systems and reports.

Please refer to the Glossary for definitions of the terms used.

Disability Status Data

Data Source

Data are from the Behavioral Risk Factor Surveillance System (BRFSS), a state-based health survey of civilian, non-institutionalized adults 18 years of age and older. The survey is conducted by all 50 states, the District of Columbia, Puerto Rico, Guam, and the U.S. Virgin Islands. With assistance from the Centers for Disease Control and Prevention (CDC), trained interviewers collect comprehensive demographic, health condition, health risk behavior, and preventive health data. Detailed information about BRFSS, including BRFSS questionnaires, codebooks, and methodology information, is available online at www.cdc.gov/brfss/.

Beginning in 2011, BRFSS made changes to both the sampling and weighting methodologies used. Prior to 2011, the BRFSS sample consisted of a random-digit dial of landline telephones and the data were weighted using post stratification. In 2011, BRFSS added cellular telephones to the sample and implemented a weighting process called iterative proportional fitting, or raking. As such, estimates from 2011 and beyond are not comparable to estimates prior to 2011. More information regarding these changes is available online at http://www.cdc.gov/surveillancepractice/reports/brfss/brfss.html.

Measures

Disability Status Indicator

Data are available for disability status. Disability questions were added to the Behavioral Risk Factor Surveillance System (BRFSS) core questionnaire in 2004. Consistent with Healthy People 2010, disability was determined using the following two BRFSS questions:

  1. “Are you limited in any way in any activities because of physical, mental or emotional problems?”
  2. “Do you now have any health problem that requires you to use special equipment, such as a cane, a wheelchair, a special bed, or a special telephone?”

Respondents were defined as having a disability if they answered Yes to either of these questions. Respondents were defined as not having a disability if they answered No to both questions.

Demographics

Data are available for eight demographic characteristics: age, sex, race/ethnicity, veteran status, income level, education level, marital status, and employment status. Please see the Demographic Data Guide for detailed information about the definitions of these measures, any specific analysis criteria, and years the data are available.

Health Indicators

Data are available for health indicators in the following categories: Health Risks & Behaviors, Prevention & Screenings, Barriers & Costs of Health Care, General Health Conditions, Chronic Conditions, Injuries, Mental & Emotional Health. To see a list of the health indicators and how they were defined, please see the Health Topic Data Guide. This guide provides detailed information about the definition, any specific analysis criteria, years the indicator data are available, and a citation if the definition was based on a publication.

Statistical Analysis

Analyses were performed using SAS (SAS Institute, Inc., Cary, North Carolina) and SAS-callable SUDAAN (Research Triangle Institute, Research Triangle Park, North Carolina) to account for the BRFSS complex survey design. All estimates were weighted to account for the probability of selection, nonresponse, noncoverage of households without a telephone, the number of adults in a household, the number of telephones in a household, and to adjust to population totals for each state or territory. Most estimates were age-adjusted to the 2000 U.S. standard population, with the exception of estimates stratified by age.1 For each indicator, Don’t Know and Not Sure responses were set to missing. Missing data were not imputed. Respondents with missing data for an indicator were not included in analyses involving that indicator. Estimates were suppressed if the standard error was greater than or equal to 30% of the estimate or if the unweighted total population was less than 50.

Data are available for all 50 states, the District of Columbia, Puerto Rico, Guam, and the U.S. Virgin Islands. Data were aggregated to produce estimates for U.S. Census divisions and regions, and the U.S. and Territories total.2

Disability Status Estimates

Disability status estimates were calculated among adults overall, and by the following demographic characteristics: age, sex, race/ethnicity, and veteran status. For each prevalence estimate, the following statistics were computed: Number, Weighted Number, Standard Error, and 95% Confidence Interval.

Demographic and Health Indicator Estimates by Disability Status

Single Year Estimates

Demographic (income level, education level, marital status, and employment status) and health indicators in DHDS were analyzed by disability status to present single year indicator prevalence estimates among adults with disability, adults without disability, and the total population of adults. The total estimate is calculated only among adults for whom disability status could be determined and is not an overall population estimate. For each prevalence estimate, the following statistics were computed: Number, Weighted Number, Standard Error, and 95% Confidence Interval. Disparity was calculated as a percentage point difference and is defined as the percentage of adults with a disability with an attribute minus the percentage of adults without a disability with that attribute.3 The p-value was calculated using a t-test examining the likelihood that the disparity is equal to zero.4 Generally, a p-value < 0.05 indicates the disparity is likely not equal to zero.

Single Year by Demographic Characteristic Estimates

Beginning with the 2011 BRFSS data, health indicator prevalence estimates by disability status also were calculated for the following demographic characteristic subgroups: age (18-44, 45-64, 65+),1 sex (male, female), and race/ethnicity (non-Hispanic white, non-Hispanic black, Hispanic, other). Within DHDS, non-Hispanic white race/ethnicity is referred to as white and non-Hispanic black race/ethnicity is referred to as black. For each prevalence estimate, the following statistics were computed: Number, Weighted Number, Standard Error, and 95% Confidence Interval.

Limitations

The estimates presented here are subject to a number of limitations. First, estimates presented are based on self-report and thus are subject to recall bias. Second, the BRFSS does not include people living in institutions or group homes. Because people with a disability are more likely to reside in such facilities, the prevalence of disability may be underestimated. Third, BRFSS is conducted only in English and Spanish and is inaccessible to individuals who require electronic telephone devices (TDD/TTY), which might preclude participation by people who speak other languages or who are deaf or hard of hearing. Fourth, BRFSS questions that are used to define disability do not collect information on the type, duration, severity, or permanence of disability.

Psychological Distress Status Data

Data Source

Data are from the Behavioral Risk Factor Surveillance System (BRFSS), a state-based health survey of civilian, non-institutionalized adults 18 years of age and older. The survey is conducted by all 50 states, the District of Columbia, Puerto Rico, Guam, and the U.S. Virgin Islands. With assistance from the Centers for Disease Control and Prevention (CDC), trained interviewers collect comprehensive demographic, health condition, health risk behavior, and preventive health data. Detailed information about BRFSS, including BRFSS questionnaires, codebooks, and methodology information, is available online at www.cdc.gov/brfss/.

Measures

Psychological Distress Status Indicator

Data are available for psychological distress status. Psychological distress questions were asked by 37 states in 2007 on an optional module, Mental Illness and Stigma. Psychological distress status was determined using the Kessler 6 (K6) scale. The K6 scale is a measure of nonspecific psychological distress experienced during the past 30 days. The scale included 6 questions asking how often during the past 30 days the respondent felt: “nervous”, “hopeless”, “restless or fidgety”, “so depressed that nothing could cheer you up”, “that everything was an effort”, and “worthless”. Possible answers to each question were: All, Most, Some, A Little, or None. These answer choices were assigned a scale of 4 (All) to 0 (None), and each respondent’s answers to the six questions were added together for a combined total ranging from 0 to 24. Respondents were then categorized by their total score, according to scoring proposed by Kessler. Serious Psychological Distress was a score of 13 or more, Mild to Moderate Psychological Distress was a score from 8 to 12, and No Psychological Distress was a score of 7 or less.

Demographics

Data are available for eight demographic characteristics: age, sex, race/ethnicity, veteran status, income level, education level, marital status, and employment status. Please see the Demographic Data Guide for detailed information about the definitions of these measures and any specific analysis criteria.

Health Indicators

Data are available for 30 health indicators in the following categories: Health Risks & Behaviors, Prevention & Screenings, Barriers & Costs of Health Care, General Health Conditions, Chronic Conditions, Mental & Emotional Health. To see a list of the health indicators and how they were defined, please see the Health Topic Data Guide. This guide provides detailed information about the definition, any specific analysis criteria, and a citation if the definition was based on a publication.5

Statistical Analysis

Analyses were performed using SAS (SAS Institute, Inc., Cary, North Carolina) and SAS-callable SUDAAN (Research Triangle Institute, Research Triangle Park, North Carolina) to account for the BRFSS complex survey design. All estimates were weighted to account for the probability of selection, nonresponse, noncoverage of households without a telephone, the number of adults in a household, the number of telephones in a household, and to adjust to population totals for each state or territory. Most estimates were age-adjusted to the 2000 U.S. standard population, with the exception of estimates stratified by age.1 For each indicator, Don’t Know and Not Sure responses were set to missing. Missing data were not imputed. Respondents with missing data for an indicator were not included in analyses involving that indicator. Estimates were suppressed if the standard error was greater than or equal to 30% of the estimate or if the unweighted total population was less than 50.

Data for the 37 states and territories with Psychological Distress Status data were aggregated to produce estimates for U.S. Census divisions and regions, and the U.S. and Territories total.6

Psychological Distress Status Estimates

Psychological distress status estimates were calculated among adults overall, and by the following demographic characteristics: age, sex, race/ethnicity, and veteran status. For each prevalence estimate, the following statistics were computed: Number, Weighted Number, Standard Error, and 95% Confidence Interval.

Demographic and Health Indicator Estimates by Psychological Distress Status

Single Year Estimates

Demographic (income level, education level, marital status, and employment status) and health indicators in DHDS were analyzed by psychological distress status to present single year indicator prevalence estimates among adults with serious psychological distress, adults with mild to moderate psychological distress, adults without psychological distress, and the total population of adults. The total estimate is calculated only among adults for whom psychological distress status could be determined and is not an overall population estimate. For each prevalence estimate, the following statistics were computed: Number, Weighted Number, Standard Error, and 95% Confidence Interval. Disparity – Serious Psychological Distress was calculated as the percentage point difference in the prevalence estimates among adults with serious psychological distress and adults without psychological distress. Disparity – Mild to Moderate Psychological Distress was calculated as the percentage point difference in the prevalence estimates among adults with mild to moderate psychological distress and adults without psychological distress

Limitations

The estimates presented here are subject to a number of limitations. First, estimates presented are based on self-report and thus are subject to recall bias. Second, the BRFSS does not include people living in institutions or group homes. Because people with a disability are more likely to reside in such facilities, the prevalence of disability may be underestimated. Third, BRFSS is conducted only in English and Spanish and is inaccessible to individuals who require electronic telephone devices (TDD/TTY), which might preclude participation by people who speak other languages or who are deaf or hard of hearing. Fourth, BRFSS questions that are used to define psychological distress do not collect information on a lifetime diagnosis of specific mental disorders.

Expenditures

Disability-Associated Health Care Expenditures (DAHE) are health care costs related to injury, diseases, and chronic conditions that are associated with a person’s disability, exclusive of non-disability related costs. DHDS contains data on two pieces of information related to DAHE: health care expenditures associated with disability, and mean per capita DAHE.

Health care expenditures associated with disability presents mean health care expenditures that are associated with disability by four payer types: Total Expenditures, Medicare, Medicaid, and Nonpublic Source payer. Estimates represent the proportion of the total expenditures in that payer type that are DAHE. Estimates are presented in percentages and millions of 2006 dollars.

Mean DAHE per capita presents mean expenditures per person, regardless of whether they have a disability. The state total DAHE is divided by the total population in that state. Estimates are available at state-level and for the entire United States. Mean per capita expenditures are presented in 2006 dollars.

For more information, please see:
Anderson WL, Armour BS, Finkelstein EA, Wiener JM. Estimates of state-level health-care expenditures associated with disability. Public Health Rep. 2010;125:44–51.

Notes

1 Although most indicators were age-adjusted or stratified using the following age groups: 18-44, 45-64, and 65+, these age groups do not apply to all indicators. More information on age-adjustment and additional age groups is available in Analytic Considerations for DHDS Estimates, available from Additional Information.

2 Disability Status data are not available for all states and territories for all years. The following states or territories did not participate in the BRFSS for a given year(s): Hawaii (2004), Guam (2004-2006), U.S. Virgin Islands (2012). 2011 data are not available for the U.S. Virgin Islands, as their sample did not include cellular telephones. 2011 data are also not available for Guam because of a delay in releasing the final data file. These states and territories appear in DHDS as NA and are not part of the divisional, regional, and total estimates for those years indicated.

3 Disparity estimates were calculated before rounding the disability specific estimates and therefore may not match disparities calculated by subtracting the rounded disability specific estimates available in DHDS.

4 P-values are available beginning with the 2011 BRFSS data.

5 Although the Health Topic Data Guide has definitions for all indictors in DHDS, only health indicators with data for 2007 will have Psychological Distress Status Data.

6 Psychological Distress Status data are only available for 2007 for the following 37 states and territories: Alaska, Arkansas, California, Colorado, Connecticut, District of Columbia, Georgia, Hawaii, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Mexico, Ohio, Oklahoma, Oregon, Rhode Island, South Carolina, Texas, Vermont, Virginia, Washington, Wisconsin, Wyoming, and Puerto Rico. States and territories that do not have data for Psychological Distress appear in DHDS as NA and are not part of the divisional, regional, and total estimates.

 
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