While there are a number of ways to measure health outcomes and losses in health associated with chronic diseases, the measured used here are lost Quality Adjusted Life Years (QALY). The QALY is a generic measure of disease burden, including both the quality and the quantity of life lived. It assumes that health is a function of length of life, quality of life, and that these can be combined in to single index number that represents an ordinal measure of health.
To determine a QALY, a “utility” value associated with a given state of health is multiplied by the years lived in that state. The utility values vary from 1 (Full Health) to 0 (Death) and, in some cases, below 0 (for health states that are rated as being ‘worse than death’). The QALY is utility score multiplied by the number of years in that health state. For instance, if an individual with a chronic disease has a utility score of .5 and lives for 5 years, then their QALY is 2.5 (= 5 years x .5 utility score).
The ‘lost QALYs’ from chronic diseases represent the difference between the QALYs of a healthy person and the QALYs of a person with a chronic condition. One way to calculate the lost QALYs is to compare the QALYs of a healthy person and the QALYs of a person with a chronic disease across their lifespan. For instance, if utility score of a health person aged 68 was .8 and she lived in that state for 10 years, and if the utility score of a person with a chronic disease was .5 and she lived in that state for 5 years, then the ‘loss in QALYs’ from the chronic disease would 5.5 QALYs lost, or the difference between the health person’s QALYs (8 = .8 x 10 years) and the person with the chronic disease (2.5 = .5 x 5 years). And if there were 100 similar people in a targeted population with this chronic condition, then the total lost QALYs would be 550 (100 people x 5.5 QALY loss).
An alternative way to identify the health loss for a group is to take all the people in a given year with a chronic condition, compare their utility score to the utility scores of a matched group of health people, and then add up the lost utility in that year. For instance, if there were three people with a chronic disease who had a utility scores of .5, .4, and .3, and match healthy counterparts (i.e., controlling for age, gender, and ethnicity) who had utility scores of .8, .7. and .6, then the total utility loss for this group in a given year would be .9 (= (.8 - .5) + (.7 - .4) + (.6 - .3)). If there were 100 people in this targeted group, then the total utility loss would be 90 (= .9 x 100). Note the time frame for this assessment is 1 year, 90 represents the ‘lost QALYs’ for this group in this year.
Because of the nature of the available data, the TOOL uses the latter approach to estimate lost QALYs. That is, the health outcome loss reported by the TOOL are the cumulative difference between the utility sores of people in the target group (e.g., county or region, age or age range, gender, ethnicity, and type of condition) and healthy counterparts.
Details of the method for calculating the utility scores for chronic diseases and health counterparts are described elsewhere. Briefly, a predictive model for the estimation of health utility scores for several chronic diseases based on age, gender, and ethnicity were determined after a meta-analyzed 385 health utility scores from 30 different studies for one of six chronic diseases: arthritis, asthma, cancer, depression, diabetes, and heart disease (including stroke and hypertension). A conditional random-effects multilevel meta-analytic model was fitted to develop a predictive model to aid in producing QALY estimates for cost effectiveness analysis.
The choice of a monetary value for a quality adjusted life year (QALY) depends in part on the preferences and resources available to the funder. In the US, the common the value is often set at $50,000 although there is some evidence that it can higher, and other evidence that it is now much less. The TOOL uses $50,000 as the default value but allows the user to enter an alternative value if desired.
The basic formula for estimating the lost health outcomes (lost QALYs) per county is as follows:
Number of people with the chronic disease in the county by age, gender, and ethnicity
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Utility loss for each chronic disease by age, gender, and ethnicity
= Lost QALYs from each chronic disease per county
The monetary value of the lost QALYs was calculated as follows:
Lost QALYs from each chronic disease per county
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Monetary value per lost QALYs
= Monetary value per lost QALYs by condition by county