Disparities in CKD Prevalence in a Universal Healthcare Coverage Setting

Patients with chronic kidney disease (CKD) commonly progress to kidney failure and the need for renal replacement therapy. There are strong and well-documented associations between health-impeding social determinants of health (i.e., social risks) and the incidence, prevalence, and progression of CKD. There are also substantial disparities in racial and socioeconomic factors that characterize CKD.

Poverty fuels social risks and combines and interacts with clinical and biological factors, resulting in poor health outcomes, including CKD. In the general population in the United States, particularly among low-income individuals, inadequate access to healthcare is a social risk affecting health outcomes. In 2017, 7.4% of the total US population, including 16.2% of those living below the federal poverty level, delayed or missed necessary medical care due to cost. There are associations between poor outcomes in CKD and being underinsured or uninsured.

In some medical conditions, racial and socioeconomic disparities seem to be mitigated with universal healthcare coverage. However, in CKD, racial disparities often persist despite universal access to care. According to Jenna M. Norton, PhD, MPH, and colleagues, socioeconomic disparities in CKD remain in settings with universal healthcare coverage, including the United Kingdom, Denmark, and Australia.

The researchers conducted a cross-sectional study to examine the role of healthcare access in racial and socioeconomic disparities in CKD and the extent to which socioeconomic factors and race are associated with CKD in the context of universal healthcare coverage. The study was designed to test the hypothesis that CKD prevalence would be elevated in beneficiaries of Black versus White race, lower versus higher rank (as a proxy for socioeconomic status and social class), lower-income versus higher-income areas, and unmarried versus married status. Results were reported in Kidney Medicine [2022;4(1):1-10].

The study utilized data from the Military Health System (MHS) Data Repository (MDR) via the Comparative Effectiveness and Provider Induced Demand Collaboration project. The MDR includes data for all in-patient and out-patient visits for the approximately 9.5 million MHS beneficiaries who receive care paid for by the military’s TRICARE Health plan.

The study sample included all patients 18 to 64 years of age who received healthcare through the MHS between October 2, 2105, and September 30, 2018, including active-duty military personnel and their dependents, retired military personnel and their dependents, and dependent survivors. Beneficiaries ≥65 years of age were excluded because Medicare, rather than TRICARE, is the primary payer for that age group.

The primary outcome of interest was CKD, defined by the presence of an International Classification of Diseases, Tenth Revision code for CKD and/or a validated laboratory value-based electronic phenotype. Comparisons of CKD prevalence by the predictors of interest (race, sponsor’s rank, median household income by sponsor’s zip code, and marital status) were examined using multivariable logistic regression after controlling for confounders (age, sex, active-duty status, sponsor’s service branch, and depression) and mediators (hypertension, diabetes, HIV, and body mass index [BMI]).

The study population included 3,330,893 MHS beneficiaries. Mean age was 33 years and mean BMI was 28 kg/m². Of the total population, 55% were White (n=1,827,435), 15% were Black (n=493,390), 10% were other race (n=314,683), 5% were Asian American and Pacific Islander (n=149,828), and 0.6% were American Indian and Alaska Native (n=21,461) beneficiaries; 16% of the population had missing or unknown race data. Fifty-two percent of the population was active duty, 36% were dependents, and 12% were retired.

Of the total study population, 3.32% (n=105,504) had CKD. Compared with those without CKD, those with CKD were on average older, less likely to be active duty, more likely to be retired, morel likely to be Black, more likely to be senior enlisted or a senior officer, and more likely to be married. Those with CKD also had a higher average BMI and were more likely to have hypertension, diabetes, and depression than those without CKD. Nearly all of those with CKD (99%) had one measure of estimated glomerular filtration rate in the MDR; only 50% had a measure of proteinuria.

Following adjustment for confounders, Black beneficiaries had 1.67 times higher odds of prevalent CKD compared with their White counterparts (odds ratio [OR], 1.67; 95% confidence interval [CI], 1.65-1.70). Following adjustment for suspected mediators, the association was partially but not totally mitigated (OR, 1.30; 95% CI, 1.28-1.32). CKD prevalence was lower in single versus married beneficiaries (OR, 0.77; 95% CI, 0.76-0.79).

Compared with very high median household income quintile, the high quintile had 1.40 (95% CI, 1.36-1.44) times greater odds of CKD, the medium quintile had 1.98 (95% CI, 1.94-2.02) times greater odds of CKD, the low quintile had 2.76 (95% CI, 2.70-2.82) times greater odds of CKD, and the very low quintile had 2.58 (95% CI, 2.52-2.64) times greater odds of CKD. Following further adjustment for suspected mediators, the magnitude of the association was attenuated but remained significant for all income levels. The prevalence of CKD was increased among those with a lower rank and those with a lower media household income in a nearly dose-response fashion (P<.0001).

In sensitivity analyses, the overall pattern of increased prevalence of CKD among Black beneficiaries, beneficiaries of lower rank, and beneficiaries living in lower-income areas remained consistent.

Limitations to the analysis cited by the authors included the cross-sectional design, the lack of data for laboratory tests conducted outside the MHS, and the use of a specific definition of CKD that may have led to an underestimation of CKD prevalence. Further, the accuracy of zip code-level median household income data may have been limited by the transient nature of the MHS population.

In conclusion, the researchers said, “Despite the universal healthcare coverage provided through the MHS, racial and socioeconomic CKD disparities exist in this population. Our findings are consistent with racial and socioeconomic CKD disparities identified in other domestic and international settings that provide universal healthcare coverage., Genetic differences may partially account for the racial differences in CKD in insured populations. However, the existence of disparities by rank and zip code-level median household income suggests that socioeconomic status, social class, and associated social risks may increase the risk for CKD despite access to universal healthcare coverage. Therefore, access to healthcare coverage alone may not be sufficient, and broader interventions to address social risk factors may be necessary to significantly mitigate racial and socioeconomic CKD disparities.”

Takeaway Points

1. Researchers conducted a cross-sectional study to examine racial and socioeconomic disparities in the prevalence of CKD in a large, diverse population with universal healthcare coverage.
2. CKD prevalence was higher among Black beneficiaries compared with White beneficiaries and lower in single versus married beneficiaries.
3. Among those with a lower military rank and those with a lower median household income, CKD prevalence was increased in a nearly dose-response fashion.