The Effect of Medicaid Expansion on Self-Reported Kidney Disease

Research Letter

Patients with CKD have low awareness of their CKD status. In the National Kidney Foundation’s Kidney Early Evaluation Program (KEEP), only 8.1% of adults with hypertension, diabetes, or a relevant family history were aware of their CKD (1). This was concordant with estimates from the National Health and Nutrition Examination Survey in which CKD awareness was 6.4% between 1999 and 2014 (2). Kidney disease disproportionately affects low socioeconomic groups who are more likely to lack health insurance; however, data on the effect of health insurance coverage on CKD awareness are limited. A cross-sectional analysis of KEEP data found that although lack of health insurance and perceived difficulty obtaining medical care were common in patients with CKD, availability of health insurance was not associated with CKD awareness (3,4). The causal effect of other factors, such as having a primary care physician and routine checkups on CKD awareness, has not been investigated.

The Affordable Care Act resulted in the expansion of Medicaid coverage in participating states to nonelderly adults with an income <138% of the federal poverty line. In this study, we assessed the effect of Medicaid expansion on self-reported kidney disease using a quasi-experimental design. We assume that CKD prevalence did not change over time, making self-reported kidney disease a proxy for CKD awareness (2,5).

Our sample included low-income (<138% federal poverty line), nonelderly (age <65 years) adults in the Behavioral Risk Factor Surveillance System (BRFSS) survey between 2012 and 2017, residing in 46 states. We included low-income, nonelderly adults as this population was targeted by the Affordable Care Act. We excluded participants residing in four states and the District of Columbia that expanded Medicaid before 2014. The primary outcome was self-reported kidney disease, assessed by the question “Has a doctor, nurse, or other health professional ever told you that you have kidney disease? Do NOT include kidney stones, bladder infection, or incontinence.” As health care access may affect self-reported kidney disease, we assessed the prevalence of having health care coverage, a personal doctor, and a routine checkup within the past year. We used difference‐in‐differences (DiD) analyses to evaluate self-reported kidney disease and health care access in Medicaid expansion states compared with nonexpansion states. To examine changes over time, we quantified the changes in self-reported kidney disease in pre-expansion (2012–2013), immediate postexpansion (2014–2015), and late postexpansion (2016–2017) time periods. We performed multivariable, logistic regression adjusting self-reported kidney disease for kidney disease risk factors, including demographics, smoking status, and comorbidities. We performed sensitivity analyses by restricting the sample to two high-risk groups: participants with hypertension or diabetes. All analyses accounted for the complex survey design and weighted sampling probabilities of the data.

Participants in expansion states (24 states; n=269,456) were less likely to be black (13% versus 22%) and were similar in age (25% versus 26% aged 50–64 years) and sex (49% versus 49% men) compared with those in nonexpansion states (19 states; n=229,907). Prevalence of hypertension (25% versus 28%; P<0.001), diabetes (9% versus 10%; P<0.001), and cardiovascular disease (6% versus 7%; P<0.001) was lower in expansion compared with nonexpansion states. Self-reported kidney disease was 2.7% in both expansion and nonexpansion states in 2012–2013, consistent with very low CKD awareness (2). There was no difference in self-reported kidney disease in expansion compared with nonexpansion states, in both the immediate and late expansion periods with adjustment for kidney disease risk factors (late postexpansion DiD estimate 0.2%; P=0.63; Table 1). Restricting the sample to participants with hypertension or diabetes did not show an increase in self-reported kidney disease. The prevalence of having health care coverage increased over time in expansion compared with nonexpansion states (baseline 64.1%; late postexpansion DiD estimate 4.7%; P<0.001). Participants that had a personal doctor increased in expansion states compared with nonexpansion states (baseline 60.9%; late postexpansion DiD estimate 2.7%; P<0.001), as did the prevalence of having a routine checkup within the past year (baseline 56.8%; late postexpansion DiD estimate 1.9%; P=0.004).

Table 1.

Changes in self-reported kidney disease and health care access for low-income, nonelderly adults in pre-expansion (baseline), immediate postexpansion, and late postexpansion periods

Outcome	Pre-Expansion Baseline (2012–2013), Mean % in Expansion Statesa	Immediate Postexpansion (2014–2015), Difference-in-Differences Estimate (95% CI)	P Value	Late Postexpansion (2016–2017), Difference-in-Differences Estimate (95% CI)b	P Value
Self-reported kidney diseasec
All participants, n=499,002	2.7%	0.3% (−0.3 to 0.9)	0.36	0.2% (−0.5 to 0.8)	0.63
History of hypertension, n=79,776	6.8%	0.8% (−1.1 to 2.6)	0.41	0.7% (−1.1 to 2.6)	0.45
History of diabetes, n=57,685	9.9%	1.1% (−2.7 to 4.9)	0.57	1.1% (−2.2 to 4.5)	0.52
Health care access
Have health care coverage, n=498,627	64.1%	4.3% (3.1 to 5.6)	<0.001	4.7% (3.4 to 5.9)	<0.001
Have a personal doctor, n=498,540	60.9%	2.0% (0.7 to 3.3)	0.002	2.7% (1.4 to 4.0)	<0.001
Routine checkup within past year, n=484,470	56.8%	1.7% (0.4 to 3.0)	0.01	1.9% (0.6 to 3.2)	0.004

Difference‐in‐differences estimates are for expansion states. Nonexpansion states (n=19) were Alabama, Florida, Georgia, Idaho, Kansas, Maine, Mississippi, Missouri, Nebraska, North Carolina, Oklahoma, South Carolina, South Dakota, Tennessee, Texas, Utah, Virginia, Wisconsin, and Wyoming. Alaska, Louisiana, and Montana were included as nonexpansion states for the immediate postexpansion period (2014–2015) and as expansion states for the late postexpansion period (2016–2017) because their Medicaid expansion occurred later. Delaware, District of Columbia, Massachusetts, New York, and Vermont were excluded because they expanded Medicaid in previous years. 95% CI, 95% confidence interval.

^aExpansion states (n=24) were Arizona, Arkansas, California, Colorado, Connecticut, Hawaii, Illinois, Indiana, Iowa, Kentucky, Maryland, Michigan, Minnesota, Nevada, New Hampshire, New Jersey, New Mexico, North Dakota, Ohio, Oregon, Pennsylvania, Rhode Island, Washington, and West Virginia.

^bDifference-in-differences estimates for self-reported kidney disease adjusted for patient age, sex, race/ethnicity, body mass index, smoking status, hypertension, and diabetes.

^cDifference-in-differences estimates for late postexpansion period compared with pre-expansion baseline.

After Medicaid expansion, despite increases in health insurance coverage, obtaining a personal doctor, and getting routine checkups, self-reported kidney disease did not increase. The strength of our study, in contrast to prior studies, was in the use of a quasi-experimental design, which provides evidence that improvements in health insurance and access to a primary care physician may be insufficient in improving self-reported kidney disease. As the BRFSS does not contain laboratory data, we were unable to assess state-level CKD prevalence and used self-reported kidney disease as an estimate of CKD awareness, which is a limitation of our study (6). We assumed that CKD prevalence in expansion versus nonexpansion states had similar trends. Our findings suggest that interventions beyond routine care are needed to promote CKD awareness. Further multimodal interventions beyond health insurance expansion, such as patient education targeted to high-risk patients, public health campaigns, and primary care toolkits for CKD, may be more effective in improving awareness of this asymptomatic disease.

Disclosures

Dr. Estrella, Dr. Keyhani, Dr. Leonard, and Dr. Tummalapalli have nothing to disclose.

Funding

Dr. Tummalapalli is supported by the National Institute of Diabetes and Digestive and Kidney Diseases 2T32DK007219-41 Training Grant and by the Jonathan A. Showstack Career Advancement Award in Health Policy/Health Services Research, sponsored by the Philip R. Lee Institute for Health Policy Studies at UCSF.