Health-Related Quality of Life — United States, 2006 and 2010

Matthew M. Zack, MD

Division of Population Health, National Center for Chronic Disease Prevention and Health Promotion, CDC

Corresponding author: Matthew M. Zack, Division of Population Health, National Center for Chronic Disease Prevention and Health Promotion, CDC. Telephone: 770-488-5460; E-mail: mmz1@cdc.gov.

Introduction

Health-related quality of life is physical and mental health, as perceived by a person or group of people, during a period of time (1,2). This measure complements traditional public health measures of mortality and morbidity. Fair or poor self-rated health, physically unhealthy days, and mentally unhealthy days are reported by higher percentages of women, older persons, minority racial/ethnic groups (except Asian/Pacific Islanders), and persons with less education, with lower annual household incomes, who are unemployed, with a disability or a chronic disease, and who are widowed, separated, or divorced than, respectively, men, younger persons, and non-Hispanic whites, and those with more education, with higher annual household incomes, who are employed by others or self-employed, without a disability or a chronic disease, and who are married (1).

This report is part of the second CDC Health Disparities and Inequalities Report (CHDIR). The 2011 CHDIR (3) was the first CDC report to assess disparities across a wide range of diseases, behavioral risk factors, environmental exposures, social determinants, and health-care access. The topic presented in this report is based on criteria that are described in the 2013 CHDIR Introduction (4). This report provides information concerning disparities in health-related quality of life, a topic that was not discussed in the 2011 CHDIR. The purposes of this health-related quality of life report are to describe and raise awareness of how different kinds of disparities affect health-related quality of life among adults in the United States, whether and how these effects changed from 2006 to 2010 and to prompt actions to reduce disparities.

Methods

To examine health-related quality of life disparities by selected characteristics among adults (aged ≥18 years) in the United States, CDC analyzed 2006 and 2010 data from the Behavioral Risk Factor Surveillance System (BRFSS). BRFSS is a continuous, random-digit–dialed telephone survey of noninstitutionalized adults aged ≥18 years in the 50 states, the District of Columbia (DC), Puerto Rico, the U.S. Virgin Islands, Guam (5,6) (available at http://www.cdc.gov/brfss/index.htm). This analysis compares health-related quality of life measures stratified by specific characteristics in respondents from the 50 states and DC in 2006 (N = 347,790) and 2010 (N = 444,927).

Two indicators of BRFSS survey quality are its cooperation rate and its overall response rate (7,8). The cooperation rate is the proportion of all respondents interviewed of all eligible units in which a respondent was selected and actually contacted. In 2006, the cooperation rate ranged from 56.9% in California to 83.5% in Minnesota; in 2010, the cooperation rate ranged from 56.8% in California to 86.1% in Minnesota. The overall response rate is an outcome rate with the number of complete and partial interviews in the numerator and an estimate of the number of eligible units in the sample in the denominator that assumes that more unknown records are eligible, specifically, that all likely households are households and that 98% of known or probable households contain an adult who uses the telephone number. In 2006, the overall response rate ranged from 20.5% in Georgia to 58.4% in Utah, and in 2010, from 19.2% in Oregon to 57.4% in Utah.

The three health-related quality of life measures represented in BRFSS are 1) self-rated health status, 2) number of physically unhealthy days, and 3) number of mentally unhealthy days. The related BRFSS questions were as follows: 1) "Would you say that in general your health is excellent, very good, good, fair, or poor?" 2) "Now thinking about your physical health, which includes physical illness and injury, for about how many days during the past 30 days was your physical health not good?" and 3) "Now thinking about your mental health, which includes stress, depression, and problems with emotions, for about how many days during the past 30 days was your mental health not good?" CDC calculated the percentage reporting fair or poor self-rated health, mean number of physically unhealthy days, and mean number mentally unhealthy days as the primary health-related quality of life outcome measures. Respondents with the responses "do not know/not sure" or "refused to respond" were excluded from the analysis on a question-by-question basis.

Health-related quality of life disparities were assessed by stratifying results by sex, age group (18–24, 25–34, 35–44, 45–64, 65–79, and ≥80 years), race/ethnicity (non-Hispanic white, non-Hispanic black, Hispanic [might be of any race or any combination of races], non-Hispanic Asian/Pacific Islander [A/PI], non-Hispanic American Indian/Alaska Native [AI/AN], and other), educational attainment at the time of the survey (less than high school, high school graduate or equivalent, some college, and college graduate), the primary language spoken at home (English, Spanish, or other), and disability status, which was defined as an affirmative answer to either or both of the following questions (9): "Are you limited in any way in any activities because of physical, mental, or emotional problems?" and "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?") Each outcome measure was analyzed separately. Household income was not examined because educational attainment was considered a sufficient indicator of socioeconomic status for examination of disparities and because approximately 14% of BRFSS respondents did not know or refused to report household income, but <2% did not know or refused to report their educational attainment.

CDC used statistical software for the analyses to account for the stratified, complex sampling design of BRFSS (10). Data were weighted using the respondents' sampling weights based on the population of noninstitutionalized adults aged ≥18 years in their states of residence and aggregated across the 50 states and DC. Because age is associated with the health-related quality of life measures and because the age composition differs among the various categories analyzed, CDC adjusted the health-related quality of life measures by using age group categories in the specific survey year as covariates in logistic regression (for fair or poor self-rated health) and linear regression (for number of physically and mentally unhealthy days). No formal statistical testing was conducted for this analysis. Differences were assessed by calculating and comparing the 95% confidence intervals (CIs) around the age-adjusted percentages and means. In this approach, CIs were used as measure of variability, and nonoverlapping CIs were considered statistically different. Using CIs in this way is a conservative evaluation of significance differences; this might lead to a conclusion that estimates are similar when the point estimates differ at a significance level of 0.05. CIs were assessed before rounding for the tables.

Disparities were measured as the deviations from a referent group, which was the group that had the most favorable estimate for the variables used to assess disparities during the time reported. Absolute difference was measured as the simple difference between a population subgroup estimate and the estimate for its respective reference group. The relative difference, a percentage, was calculated by dividing the difference by the value in the referent category and multiplying by 100. Change in percentage and mean from 2006 to 2010 was calculated by subtracting the estimate for 2010 from the estimate for 2006. The significance of changes over time was assessed by comparing CIs as described in this section.

Results

Overall, the age-adjusted percentage of respondents rating their health as fair or poor did not change significantly from 2006 (16.3%) to 2010 (16.1%) (Table 1). A higher percentage of women than men reported fair or poor health in both years. However, neither of the groups experienced a significant change from 2006 to 2010. A higher percentage of persons in older age groups than younger groups rated their health as fair or poor in both years. The percentage of persons aged ≥65 years reporting fair or poor health significantly decreased approximately 2 percentage points from 2006 to 2010. Both in 2006 and 2010, a significantly lower percentage of non-Hispanic whites rated their health as fair or poor than all other racial/ethnic groups except A/PIs. However, only two of these racial/ethnic groups experienced a significant change in self-rated health from 2006 to 2010: the percentage of non-Hispanic blacks reporting fair or poor health increased by 2 percentage points, and that of Hispanics decreased approximately 3 percentage points. In both 2006 and 2010, a higher percentage of those who had not graduated from high school reported fair or poor health than did high school graduates, and a lower percentage of college graduates reported fair or poor health than did high school graduates. From 2006 to 2010, the percentage of high school graduates who reported fair or poor self-rated health increased by 1.2 percentage points, and the percentage of persons with some college education who reported fair or poor self-rated health decreased by 1.6 percentage points. A higher percentage of persons who spoke a language other than English at home reported fair or poor health than those who spoke English at home. However, the percentage of those who spoke Spanish at home and reported fair or poor health decreased by 7 percentage points from 2006 to 2010. A higher percentage of persons with a disability rated their health as fair or poor than did those without a disability both in 2006 and 2010. Nonetheless, the percentage of persons without a disability who rated their health as fair or poor decreased by 0.8 percentage points from 2006 to 2010.

From 2006 to 2010, the overall age-adjusted mean number of physically unhealthy days in the last 30 days increased by approximately 0.1 days (2006: 3.6 days; 2010: 3.7 days (Table 2). A higher mean number of physically unhealthy days were reported by women than men in 2006 and 2010. However, only men experienced a statistically significant increase in mean number of days (0.2 days) over time. A higher mean number of physically unhealthy days was reported by older respondents than younger respondents. From 2006 to 2010, only persons aged 25–34 years reported a statistically significant increase in mean number of physically unhealthy days (0.3 days). In both 2006 and 2010, the fewest physically unhealthy days were reported by A/PIs (2006: 2.4 days; 2010: 2.5 days) and the most were reported by AI/ANs, (2006: 6.2 days; 2010: 6.3 days). Hispanics showed an increase in mean number of physically unhealthy days from 2006 to 2010 (0.6 days). Compared with high school graduates, more physically unhealthy days were reported by those who had not graduated from high school than by those with at least some college. However, all but college graduates experienced an increase in physically unhealthy days from 2006 to 2010, with the least educated showing the largest increase (0.8 days). More physically unhealthy days were reported by those who spoke a language other than English at home than by those who spoke English at home. From 2006 to 2010, those who spoke Spanish at home had an 0.8-day increase in physically unhealthy days, compared with an almost 10-day decrease among those who spoke languages other than English and Spanish. Approximately 8 more physically unhealthy days were reported by persons with a disability (10 days) than by those without a disability (1.8 days). Neither group had a significant change in number of days from 2006 to 2010.

From 2006 to 2010, the overall age-adjusted mean number of mentally unhealthy days in the last 30 days increased by approximately 0.1 days (2006: 3.4 days; 2010: 3.5 days) (Table 3). The mean number of mentally unhealthy days for women exceeded those for men by approximately 1 day in both years. However, only men showed a significant increase from 2006 to 2010 (by 0.2 days). A higher percentage of younger respondents reported a mean number of mentally unhealthy days than older respondents. Only those aged 35–79 years experienced an increase in mean number of days from 2006 to 2010 (0.2–0.3 days). A/PIs reported the fewest mentally unhealthy days, and AI/ANs reported the most. However, from 2006 to 2010, only Hispanics showed a significant increase (0.6 days). The number of mentally unhealthy days in 2006 and 2010 was higher for persons with less education than for those with more education. However, all groups without a college degree experienced a significant increase in the number of days from 2006 to 2010. Similar to the change among Hispanic respondents, who experienced an increase of 0.6 mentally unhealthy days from 2006 to 2010, the mean number of mentally unhealthy days increased among those who spoke Spanish at home by 0.9 days. The mean number of mentally unhealthy days among persons with a disability (7 days) was approximately five more than among persons without a disability (2 days). Nonetheless, only persons with a disability showed a statistically significant increase from 2006 to 2010 (0.3 days).

Discussion

The patterns of the health-related quality of life measures among the various groups in this report are similar to previous findings (1,11). Groups with higher percentages of fair or poor health and who report more physically unhealthy days and more mentally unhealthy days are usually women, older persons (with respect to physical health), younger persons (with respect to mental health), minority racial/ethnic groups (except for A/PIs), those with less education, those who speak another language besides English at home, and those with a disability.

Groups that had statistically significant changes in health-related quality of life from 2006 to 2010 differ from groups with statistically significant differences from the reference groups during the individual years. Although minimal change occurred overall, statistically significant changes occurred in specific groups. Men (but not women) reported an increase in the number of physically and mentally unhealthy days over time. Persons aged ≥65 years rated their overall health better in 2010 than in 2006. Hispanics and those who spoke Spanish at home also rated their overall health better in 2010 than in 2006, despite reporting increases in numbers both of physically and mentally unhealthy days. Numbers of physically and mentally unhealthy days increased from 2006 to 2010 among persons without a college degree. The number of mentally unhealthy days but not of physically unhealthy days increased among persons with a disability, although persons without a disability rated their overall health better.

Reasons for particular changes in health-related quality are unclear. Differences in risky and protective health behaviors, in socioeconomic circumstances such as employment status and household income, and in disease status have been associated with differences in the measures used in this analysis to assess health-related quality of life (1,11). Hispanics and those without a college degree reported more physically and mentally unhealthy days in 2010 than in 2006; however, others in similar socioeconomic circumstances (e.g., non-Hispanic blacks and AI/ANs) did not. What accounted for these differences is unclear. Additional analyses that adjust for changes in employment status, the effects of housing loss, and the recent increase in enforcement against illegal immigrants might clarify these differences.

Limitations

The findings in this report are subject to at least four limitations. First, although the BRFSS health-related quality of life questions have been shown to be reliable in predicting 30-day and 1-year hospitalization and mortality (12,13), because the health-related quality of life data are self-reported, they might be misclassified because they are not objectively verifiable and are subject to recall bias and measurement error. Second, although BRFSS uses poststratification to adjust respondent sampling weights for non-response (7,8), this adjustment assumes that nonrespondents would have answered in similar ways to respondents with similar demographic characteristics; such poststratification might not have fully adjusted for differences between nonrespondents and respondents, given the low, state-specific overall response rates. Third, BRFSS data are cross-sectional; therefore, changes in the composition of the BRFSS sample from 2006 to 2010 that affect responses to the health-related quality of life questions might affect measured differences from 2006 to 2010. Finally, the results were adjusted for age only; therefore, other confounding variables also might have affected measured differences from 2006 to 2010.

Conclusion

Although direct interventions to improve health-related quality of life are not possible, indirect interventions to change characteristics associated with health-related quality of life might result in improvements. For example, risky health behaviors can decrease health-related quality of life. Persons who smoke cigarettes have worse health-related quality of life than former smokers or never smokers (14), and smoking is more prevalent among those with certain health conditions such as epilepsy (15).

Cigarette smoking is a well-known cause of multiple types of cancer (16). Persons with epilepsy (17) and cancer (18) have worse health-related quality of life than those without these conditions. Moreover, protective health behaviors can increase health-related quality of life. For example, persons who engage in physical activity have better health-related quality of life than those who are sedentary (19). Physical activity also reduces obesity (20) and its complications and has been associated both with reduced colon cancer rates (20) and reduced complications from different kinds of arthritis (21). Persons who are obese (22), have cancer (18), or have arthritis (23) have worse health-related quality of life than those without these conditions. Therefore, interventions to eliminate risky behaviors, promote protective behaviors, and delay or prevent complications from diseases and other conditions would probably improve health-related quality of life.

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