Geographic variation in diagnosis frequency and risk of death among Medicare beneficiaries

Abstract

Context: Because diagnosis is typically thought of as purely a patient attribute, it is considered a critical factor in risk-adjustment policies designed to reward efficient and high-quality care.

Objective: To determine the association between frequency of diagnoses for chronic conditions in geographic areas and case-fatality rate among Medicare beneficiaries.

Design, setting, and participants: Cross-sectional analysis of the mean number of 9 serious chronic conditions (cancer, chronic obstructive pulmonary disease, coronary artery disease, congestive heart failure, peripheral artery disease, severe liver disease, diabetes with end-organ disease, chronic renal failure, and dementia) diagnosed in 306 hospital referral regions (HRRs) in the United States; HRRs were divided into quintiles of diagnosis frequency. Participants were 5,153,877 fee-for-service Medicare beneficiaries in 2007.

Main outcome measures: Age/sex/race-adjusted case-fatality rates.

Results: Diagnosis frequency ranged across HRRs from 0.58 chronic conditions in Grand Junction, Colorado, to 1.23 in Miami, Florida (mean, 0.90 [95% confidence interval {CI}, 0.89-0.91]; median, 0.87 [interquartile range, 0.80-0.96]). The number of conditions diagnosed was related to risk of death: among patients diagnosed with 0, 1, 2, and 3 conditions the case-fatality rate was 16, 45, 93, and 154 per 1000, respectively. As regional diagnosis frequency increased, however, the case fatality associated with a chronic condition became progressively less. Among patients diagnosed with 1 condition, the case-fatality rate decreased in a stepwise fashion across quintiles of diagnosis frequency, from 51 per 1000 in the lowest quintile to 38 per 1000 in the highest quintile (relative rate, 0.74 [95% CI, 0.72-0.76]). For patients diagnosed with 3 conditions, the corresponding case-fatality rates were 168 and 137 per 1000 (relative rate, 0.81 [95% CI, 0.79-0.84]).

Conclusion: Among fee-for-service Medicare beneficiaries, there is an inverse relationship between the regional frequency of diagnoses and the case-fatality rate for chronic conditions.

Figure 1

Variation in Number of Chronic Conditions Diagnosed Among Medicare Beneficiaries in the United States, 2007 ^aValues in parentheses indicate range for each quintile.

Figure 2

Distribution of Chronic Conditions Among Medicare Beneficiaries Across Regions With Varying Diagnosis Frequency See Table 1 for denominator data used to calculate diagnosis frequency. ^aValues in parentheses indicate range for each quintile.

Figure 3

Population-Based Mortality and Case Fatality Across Regions With Varying Diagnosis Frequency Error bars indicate 95% confidence intervals. Relative rates of death in regions with very high vs very low diagnosis frequency: relative rate, 1.07 (95% CI, 1.06–1.08 [P=.31 for trend]) for entire population; 0.97 (95% CI, 0.94–1.00 [P=.46 for trend]) for no chronic conditions; 0.74 (95% CI, 0.72–0.76 [P=.006 for trend]) for 1 chronic condition; 0.76 (95% CI, 0.74–0.78 [P=.007 for trend]) for 2 chronic conditions; 0.81 (95% CI, 0.79–0.84 [P=.01 for trend]) for 3 chronic conditions. Entire population, N=5 153 877; no chronic conditions, n=2 611 646; 1 chronic condition, n=1 318 809; 2 chronic conditions, n=665 093; 3 chronic conditions, n=331 999; not shown are 226 300 persons with 4 or more conditions. ^aQuintiles indicate mean number of chronic conditions per beneficiary. Values in parentheses indicate range for each quintile.

Figure 4

Relative Rates of Death in Regions With Very High vs Very Low Diagnosis Frequency Among Beneficiaries Diagnosed With Each of 9 Chronic Conditions Relative rates were calculated using logistic regression adjusted for age/sex/race and number of coexisting chronic conditions and are not calculable from raw counts of numbers of deaths and numbers with each condition. CAD indicates coronary artery disease; CHF, congestive heart failure; COPD, chronic obstructive pulmonary disease; PVD, peripheral vascular disease.