Research article
Trends in Quality-Adjusted Life-Years Lost Contributed by Smoking and Obesity

https://doi.org/10.1016/j.amepre.2009.09.043Get rights and content

Background

Quality-adjusted life-years (QALYs) use preference-based measurements of health-related quality-of-life (HRQOL) to provide an assessment of the overall burden of disease using a single number.

Purpose

This study estimated QALYs lost contributed by smoking and obesity for U.S. adults from 1993 to 2008.

Methods

Population HRQOL data were from the 1993–2008 Behavioral Risk Factor Surveillance System. The QALYs lost contributed by a risk factor is the sum of QALYs lost due to morbidity in the current year and future QALYs lost in expected life-years due to premature deaths (mortality). Premature deaths were estimated from the National Health Interview Survey Linked Mortality Files and mortality statistics.

Results

From 1993 to 2008, the proportion of smokers among U.S. adults declined 18.5% whereas the proportion of obese people increased 85%. The smoking-related QALYs lost were relatively stable at 0.0438 QALYs lost per population. In 1993 the QALYs lost were much smaller for obesity compared to smoking, with obesity contributing about 0.0204 QALYs lost. However, as a result of the increasing prevalence of obesity, the contribution of obesity-related QALYs lost increased consistently and had increased by 127% in 2008 when obesity resulted in 0.0464 QALYs lost, slightly more than smoking did. Smoking had a bigger impact on mortality than morbidity, whereas obesity had a bigger impact on morbidity than mortality.

Conclusions

This study estimated the overall burden of smoking and obesity over time and results indicate that because of the marked increase in the proportion of obese people, obesity has become an equal, if not greater, contributor to the burden of disease than smoking. Such data are essential in setting targets for reducing modifiable health risks and eliminating health disparities.

Introduction

In delineating the framework and format of Healthy People 2020, the Secretary's Advisory Committee recommended that the best possible information be assembled on selected criteria that would assist users in prioritizing each health objective.1 These criteria center on the overall burden of disease (associated with a particular risk factor, determinant, disease or injury), the degree to which the burden can be prevented or reduced, and the cost effectiveness of alternative opportunities to reduce the health burden. In analyzing the health impact of risk factors, mortality or morbidity statistics such as attributable mortality and health-related quality of life (HRQOL) commonly have been used as outcome measures.2 However, as noted by the Secretary's Advisory Committee, a single measurement such as the quality-adjusted life-year (QALY) would be particularly useful in quantifying the overall health impact of risk factors using one number.1, 3

Quality-adjusted life-years use preference-based measurements of health-related quality of life (HQROL) to provide an assessment of the overall burden of diseases associated with both mortality and morbidity.4 Preference-based HRQOL measures use summary scores (i.e., utility values) to represent population preferences for different health states. Thus, 1 year of life lived at a utility score of 0.8 is equal to 0.8 QALY. The total QALYs lost contributed by a risk factor includes the QALYs lost due to nonfatal diseases (morbidity) in the current year and the future QALYs lost in the expected life-years as a result of premature deaths (mortality).5, 6, 7

Burden of disease and cost-effectiveness analyses are especially useful for quantifying the impact of particular modifiable risk factors, analyzing disparities in QALYs both at the national and local (community) levels and for small sociodemographic subgroups, and examining changes over time. However, prior to Year 2000 these analyses were not able to be conducted in the U.S. because of the lack of a data set that contained health utility scores for a representative sample of the population. During 2000–2003, the Medical Expenditure Panel Survey (MEPS) included the EQ-5D, a QALY-compatible and preference-based instrument.8 Using EQ-5D scores from the 2000 MEPS, an estimate has been made of the burden of disease attributable to obesity/overweight and low income in the general U.S. population.5, 6 However, because the MEPS included the EQ-5D between 2000 and 2003 only and was designed to provide information for the entire nation—and not for individual states or at the local level—trends over time and geographic variations were unable to be examined.

This study examined the trend of the health burden of smoking and obesity for U.S. adults from 1993 to 2008 using currently available population-based data. These two modifiable risk factors have the greatest impact on morbidity and mortality in the U.S.9, 10 The total QALYs lost were the sum of the QALYs lost due to a decrease in HRQOL score (morbidity) and the future QALYs lost in the expected life-years due to premature deaths (mortality) contributed by these two modifiable risk factors. The proposed method also can be used for examining health disparities and evaluating progress at the national, state, and local levels with regard to the upcoming Healthy People 2020 health objectives.

Section snippets

Data and Measurements

Population HRQOL data were from the 1993–2008 Behavioral Risk Factor Surveillance System (BRFSS), the largest ongoing state-based health survey of U.S. adults.11, 12 The BRFSS is a random-digit-dialed telephone survey that interviews non-institutionalized civilian adult residents aged ≥18 years to collect health-related data at the state and substate levels and to track trends over time.11, 12 In this analysis, N=3,590,540; the annual n ranged from 102,263 in 1993 to 406,749 in 2008.

Since 1993,

Results

This analysis first examined both the mean EQ-5D index scores according to obesity and smoking status and the hazard ratio for these two risk factors to analyze the impact of obesity and smoking on HRQOL (morbidity) and premature deaths (mortality), respectively (Table 1). Mean EQ-5D scores were 0.05 points lower for obese people compared to nonobese people (0.833 vs 0.883), and such a difference was much greater (about 51% higher) than the mean score difference between smokers and nonsmokers

Discussion

The overall health burden of obesity among U.S. adults has increased consistently since 1993. The finding that obesity is becoming an equal, if not greater, contributor to the burden of disease as smoking is consistent with the patterns noted in the profile of the leading causes of death.9, 21, 22 The substantial increase in the QALYs lost contributed by obesity was due to the dramatic increase in the prevalence of obesity in the U.S.23 By the final year examined (2008), the total health burden

Conclusion

This study proposes a method that uses large, currently existing data sets representative of the U.S. general adult population to calculate QALYs lost contributed by two modifiable risk factors between 1993 and 2008. This method is well timed with the HRQOL Surveillance Expert Panel's goal that relates HRQOL surveillance to the Healthy People 2020 initiative.14 Resultant data might assist in the construction of specified quantitative targets for the Healthy People 2020 health objectives and

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