Abstract
Background:
Over 12 million Americans are dually enrolled in Medicare and Medicaid. These individuals experience over twice as many hospitalizations for chronic diseases such as coronary artery disease (CAD) and diabetes, compared to Medicare-only patients. Nurse practitioners (NPs) are well-positioned to address care needs of dually-enrolled patients, yet NPs often work in unsupportive clinical practice environments. The purpose of this study was to examine the association between the NP primary care practice environment and hospitalization disparities between dually-enrolled and Medicare-only patients with chronic diseases.
Methods:
Using secondary cross-sectional data from the Nurse Practitioner Primary Care Organizational Climate Questionnaire (NP-PCOCQ) and Medicare claims files, we examined 135,648 patients with CAD and/or diabetes (20.0% dually-eligible, 80.0% Medicare-only), cared for in 450 practices employing NPs across four states (PA, NJ, CA, FL) in 2015. We compared dually-enrolled patients’ odds of being hospitalized when cared for in practice environments characterized as poor, mixed, and good based on practice-level NP-PCOCQ scores.
Results:
After adjusting for patient and practice characteristics, dually-enrolled patients in poor practice environments had the highest odds of being hospitalized compared to their Medicare-only counterparts (OR 1.48, CI: 1.37, 1.60). In mixed environments, dually-enrolled patients had 27% higher odds of a hospitalization (OR 1.27, CI 1.12, 1.45). However, in the best practice environments, hospitalization differences were non-significant (OR 1.02, CI 0.85, 1.23).
Conclusions:
As policymakers look to improve outcomes for dually-enrolled patients, addressing a modifiable aspect of care delivery in NPs’ clinical practice environment is a key opportunity to reduce hospitalization disparities.
Keywords: primary care, disparities, dual-eligible, nurse practitioners, work environment
INTRODUCTION
The 12 million Americans who are dually-enrolled for Medicare and Medicaid – disproportionately low-income, racial/ethnic minorities, disabled, and older adults – are over 60% more likely to be hospitalized compared to those insured solely by Medicare.1–3 While dually-enrolled and Medicare-only patients experience a similar prevalence of chronic diseases, dually-enrolled patients have twice the odds of being hospitalized compared to their Medicare-only counterparts.1,2,4,5 Accessible primary care inclusive of chronic disease management, patient education, and care coordination may reduce hospitalizations amongst dually-enrolled patients with chronic diseases by ensuring they have the resources and support needed to manage their conditions at home.6–8 However, barriers exist limiting dually-enrolled patients from accessing primary care. Most states cap reimbursements for dually-enrolled patients at the Medicaid fee, disincentivizing providers from caring for these patients.9,10 Socioeconomic constraints, such as a lack of available transportation or unaffordable copays, may also prevent dually-enrolled patients from accessing primary care.1,2 As a result, dually-enrolled patients may be disproportionately limited from receiving necessary primary care and chronic disease management, potentially contributing to disparities in hospitalizations.9–11
Nurse practitioners (NPs) are uniquely poised to address the primary care needs of dually-enrolled individuals. NPs are the fastest-growing segment of the primary care workforce and disproportionately provide primary care for dually-enrolled individuals.12–14 Nurse practitioners’ model of care prioritizes a holistic, person-centered care approach, including addressing social determinants of health and integrating cultural preferences into care, which may especially align with dually-enrolled individuals’ care needs.1,3,14–16 Yet, despite NPs’ potential to improve care for dually-enrolled patients, their care may be hindered by constraints in the practice environments within which they work.14,15,17 Supportive NP practice environments are characterized by strong relationships and communication with administrations and physician colleagues, professional visibility and autonomy, and sufficient organizational resources.17,18 Studies have demonstrated that many practices where NPs work lack these organizational features.14,18–20 For example, some primary care practices may not provide the same organizational supports (e.g., scribes for clinical notes) for NPs as they do for physicians.17 These cross-disciplinary inequities can lead to NP burnout and turnover and negatively impact care for NPs’ patients, who are disproportionately low-income, Medicaid-insured, and live with multiple chronic conditions.1,3,12,13 Studies have shown that when NPs work in supportive environments, patients receive higher-quality primary care and have better outcomes, such as reduced emergency department visits.14,16,19,20
The influence of organizational clinical environments for healthcare providers, including NPs, on improving patient outcomes has been well-documented.16,21–24 While studies have linked practice environments that are supportive of NPs with high-quality chronic disease management and improved outcomes19,20,24 22,23,28, little attention has been paid to how improvements in the NP practice environment may reduce disparities, such as hospitalization disparities between dually-enrolled and Medicare-only patients. Given that dually-enrolled patients have higher rates of hospitalizations compared to Medicare-only patients and that dually-enrolled patients are disproportionately cared for by primary care NPs, this population may be particularly sensitive to changes in the NP practice environment.3,10 Therefore, the purpose of this study is to examine the relationship between the NP practice environment and hospitalization disparities between dually-enrolled patients and Medicare-only patients with chronic diseases. We posit that while all patients may benefit from improving the NP practice environment, such benefits may be especially important for dually-enrolled patients.
METHODS
Design
This was a cross-sectional, observational study of 135,648 patients who were cared for in 450 primary care practices across four states (California, Pennsylvania, New Jersey, and Florida) in 2015. We linked surveys of NPs on their practice environment with Medicare claims data to assign patients to the practices where they received primary care. This study was approved by the (removed for review) Institutional Review Board.
Survey Participants and Data Collection.
Nurse practitioner data were obtained from the 2015 RN4CAST-US-NP survey. Details on survey data collection procedures and response rate are described elsewhere16,24; in brief, we surveyed a 50% random sample of NPs in each of the four states using a modified Dillman approach.25 These four states were selected due to their large size, varying geographic regions in the United States, and large numbers of NPs licensed in each state.26
To prevent organizational selection bias, we obtained NP addresses from state boards of nursing and mailed surveys directly to NPs’ homes.27 This method is preferable to surveying NPs through their organizations, as practice managers perceiving their organizations to be low-performing may be disinclined to share our survey with their NPs.27 Approximately 6,500 NPs across settings responded to the survey (30% response rate).28 A nonresponse analysis showed no major differences between responders and eligible nonresponders.26
Primary care practices with at least one NP survey respondent were included in the present analysis if they were classified as family, internal, or geriatric medicine or multi-specialty, a method previously employed by studies using SK&A data.29,30 Consistent with an existing definition, we defined NP primary care settings as offices, home health, community health clinics, health departments, long-term care, school health, hospital outpatient departments, nursing offices, correctional facilities, or Veterans Affairs/Department of Defense clinics.31 NPs were asked about demographics, the name and address of their practice, and practice characteristics, including the type of practice, their practice environment, whether they bill for services under their own National Provider Identifier (NPI), and daily volume of patients seen.16,26 For practices with more than one NP respondent, responses were aggregated to the practice level.16,19,20,24
Patient Sample
We derived our patient sample from Medicare claims data for fee-for-service beneficiaries continuously enrolled in Medicare parts A and B in 2015 who had at least one claim filed by a provider in a practice represented in the NP survey data. We requested data of a random sample of 1,000,000 Medicare beneficiaries who received primary care from one of our practices. Claims data include patient demographics, diagnosis and procedure codes, hospitalizations and office visits, and the presence of each of the 27 chronic conditions defined by the Chronic Conditions Warehouse.32 Patients were included if they were 18 or older, were alive at the end of 2015, had at least 1 visit to a provider in one of our practices during the year, and had 2 or more claims for either CAD or diabetes using International Classification of Disease (ICD-9 and ICD-10) codes.33–35 These conditions were chosen as they are two of the most common chronic diseases affecting Medicare-enrolled patients.
Conditions under the CAD diagnosis, such as ischemic heart disease and atherosclerosis, were derived from the National Committee for Quality Assurance’s (NCQA) definition of CAD claims.36 Conditions under the diabetes diagnosis were identified by the Agency For Healthcare Research and Quality’s Prevention Quality Indicators (PQIs) definition of diabetes claims.37 We opted to use these definitions, as these sets of diagnostic codes were developed to identify those conditions for which health outcomes should be amenable to high-quality primary care. A full list of included codes is in Appendix A. Patient claims were merged with the Medicare Provider Analysis and Review (MedPAR) file to determine which of those patients did or did not experience a hospitalization in 2015.
Data Linkage and Patient Attribution
Nurse practitioner surveys and Medicare claims were linked via the SK&A database on primary care practices. This database is a proprietary national dataset containing practice-level (e.g., specialty, patient volume, and insurance types accepted) and provider-level (e.g., NPI numbers) information.38 Nurse practitioner surveys were linked to the SK&A file using practice addresses. Patients were attributed to their primary care providers using a previously-established attribution methodology, as patients may have been seen by multiple providers in our dataset.12,39
First, we connected patient claims to the providers who filed each claim using NPI numbers of physicians, NPs, and physician assistants (PAs). Next, we used the Practice Identifier in SK&A to situate providers in practices, allowing us to connect claims data to the practices represented in our survey data. Then, we calculated the proportion of primary care evaluation & management (E&M) codes filed by each provider and determined which provider filed the highest percentage of claims for that patient. Consistent with prior literature, the E&M codes used to establish attribution were limited to new and established office visits, home and nursing home visits.12,31 We also included multi-specialty visits as many primary care practices were multi-specialty. Finally, we attributed patients to the provider (physician, NP, or PA) who filed the highest percentage of claims, so long as that provider filed at least 30% of that patient’s claims.12,20
Variables
Our outcome variable was all-cause hospitalization, using the first hospitalization of record in 2015.12,20 Dually-enrolled status was measured as being insured by Medicare for the entire year, and, per the Chronic Condition Warehouse Technical Guidance, eligible for Medicaid coverage for ≥ 1 month in 2015.40 The latter criterion was selected as dually-eligible status is highly variable due to changing state-level Medicaid-eligibility policies, yet individuals who spend any amount of time dually-enrolled tend to be of low income and with multiple chronic conditions.41
The primary explanatory variable was the NP practice environment, measured using the 29-item Nurse Practitioner-Primary Care Organizational Climate Questionnaire (NP-PCOCQ).18 The NP-PCOCQ and its subscales have demonstrated strong internal consistency reliability and discriminant and predictive validity.16,19,20,24,42,43 The scale asks NP respondents to rate their practice on a four-point Likert scale on the presence of certain organizational characteristics.18 Example questions include: NPs and physicians collaborate to provide patient care, my organization creates an environment where I can practice independently, administration takes NP concerns seriously, and the NP role is well understood. These questions are grouped into four subscales: Professional Visibility, NP-Physician Relations, NP-Administration Relations, and Independent Practice and Supports. Each subscale score is calculated by averaging responses to questions within that subscale, and the total score for an individual nurse is the average of the four subscales, with higher scores indicating more favorable environments. Practice-level means were derived by aggregating the responses of all NPs in each practice. All subscales in our sample had acceptable internal consistency reliability as demonstrated by the following Cronbach α scores: 0.80 (Professional Visibility), 0.82 (Independent Practice & Supports), 0.78 (NP-Administration Relations), and 0.85 (NP-Physician Relations). Next, we categorized the NP practice environment based on the number of subscales that were above the median. Practice environments were identified as being poor (0–1 subscale above the median), mixed (2–3 subscales above the median), and best (4 subscales above the median), as in prior studies.16,24
Risk Adjustment
We accounted for several patient and practice-level characteristics that may serve as confounders. Our study accounts for practices across four states that have a varying scope of practice laws for NPs.45 California and Florida are considered restrictive practice states, meaning physician supervision is required and at least one element of NP practice is restricted (i.e., the ability to prescribe medications). Pennsylvania and New Jersey are considered reduced practice states, meaning that a collaborative agreement with physicians is required, and at least one element of NP practice may be reduced.44 We thus account for these differences in our model by using state of practice as a covariate, especially as evidence shows an association between state-level scope of practice (SOP) and organizational-level practice environment, patient outcomes, and quality of care.45 Other potential practice-level confounders adjusted for in analyses included practice specialty, daily patient volume, and whether or not the practice accepts Medicaid, all of which came from SK&A, and the percentage of dually-enrolled individuals in each practice, calculated through claims data.. Patient-level risk adjustment included patient age, sex, and presence of the 27 chronic conditions. Since dually-enrolled individuals are disproportionately racially minoritized individuals (especially Black and Hispanic individuals)1, we included race/ethnicity as a covariate and to determine if there was a main effect.
Data Analysis
We compared patient and practice characteristics between dually-enrolled and Medicare-only patients using t-tests for continuous and chi-squares for categorical variables. Finally, we used logistic regression models to assess the relationship between practice-level work environment and hospitalization. We account for the clustering of 135,648 patients nested in 450 practices using Huber-White procedures.46 The first model estimated the unadjusted association between dually-enrolled status and hospitalization, while the second model included adjustments for practice-level characteristics (including the practice environment) and the third for both practice and patient-level characteristics. To determine if the NP practice environment differentially influenced hospitalizations between dually-enrolled and Medicare-only patients, we conducted a final, fully-adjusted model including an interaction term between dually-enrolled status and the three-level NP practice environment. For a significant interaction term, a priori pairwise comparisons were performed to determine at which levels of the practice environment there were significant differences in hospitalizations. Finally, as a sensitivity analysis, we examined the influence of the NP practice environment on hospitalizations separately for dually-enrolled and Medicare-only individuals, adjusting for patient and practice characteristics. We used STATA 15 for all analyses (Stata Statistical Software: Release 15, StataCorp, 2017, StataCorp LLC, College Station, TX).
FINDINGS
Our final sample consisted of 135,648 patients with CAD or diabetes (20.0% dually-enrolled, 80.0% Medicare-only), who were cared for at 450 primary care practices with at least 1 NP survey respondent. Table 1 displays patient characteristics of dually-enrolled and Medicare-only patients. Overall, dually-enrolled patients were younger, more likely to be hospitalized, and more likely to be female and non-white (including Black, Asian, Hispanic, & North American Native). In our sample, dually-enrolled patients were more likely to have diabetes, and Medicare-only patients were more likely to have CAD. There was no difference in-office visits, and dually-enrolled patients had just slightly more chronic conditions than Medicare-only patients (6.1 vs. 5.9, p <.001). Table 1 also presents the top 10 comorbidities across the sample.
Table 1.
Characteristics of Dually-Enrolled and Medicare-Only Patients with Coronary Artery Disease and Diabetes
| Characteristics | Total Sample (N=135,648) |
Dually-Enrolled (n=27,126; 20.0%) |
Medicare-Only (n=108,522; 80.0%) |
p |
|---|---|---|---|---|
| Age in years, mean (SD) | 74.5 (10.3) | 68.7 (13.6) | 76.0 (8.7) | <.001 |
| Male, n (%) | 67,788 (50.0) | 10,480 (38.6) | 57,308 (52.8) | <.001 |
| Race, n (%) | <.001 | |||
| White | 108,575 (80.4) | 13,907 (51.3) | 94,668 (87.2) | |
| Black | 9,479 (7.0) | 4,226 (15.6) | 5,253 (4.8) | |
| Asian/Pacific Islander | 4,426 (3.3) | 1,975 (7.3) | 2,451 (2.3) | |
| Hispanic | 411,516 (8.4) | 4,840 (4.5) | 6,676 (24.6) | |
| North American Native | 296 (0.2) | 122 (0.4) | 174 (0.2) | |
| Other | 1,356 (1.0) | 220 (0.8) | 1,136 (1.0) | |
| Reason for entitlement, n (%) | <.001 | |||
| Age > 64 | 120,522 (88.9) | 17,783 (65.6) | 102,739 (94.7) | |
| Disability | 14,113 (10.4) | 8,663 (31.9) | 5,450 (5.0) | |
| End stage renal disease | 535 (0.4) | 355 (1.3) | 180 (0.2) | |
| Disability and end stage renal disease | 478 (0.4) | 325 (1.2) | 153 (0.1) | |
| Hospitalized, n (%) | 40,586 (29.9) | 11,090 (40.9) | 29,496 (27.2) | <.001 |
| Had a primary care visit, n (%) | 133,350 (98.3) | 26,521 (97.8) | 106,829 (98.4) | <.001 |
| Chronic disease, n (%) | ||||
| CAD | 78,868 (58.1) | 13,590 (50.1) | 65,278 (60.2) | <.001 |
| Diabetes | 98,158 (72.4) | 22,753 (83.9) | 75,405 (69.5) | <.001 |
| Total chronic conditions, mean (SD) | 6.3 (2.9) | 6.6 (3.3) | 6.3 (2.8) | <.001 |
| Top 10 comorbidities, n (%) | ||||
| Hypertension | 115,855 (85.4) | 23,091 (85.1) | 92,764 (85.5) | 0.139 |
| Hyperlipidemia | 108,245 (79.8) | 19,346 (71.3) | 88,8999 (81.9) | <.001 |
| Ischemic heart disease | 81,374 (60.0) | 13,824 (51.0) | 67,550 (62.3) | <.001 |
| Anemia | 57,634 (42.5) | 13,712 (50.6) | 43,922 (40.5) | <.001 |
| Rheumatoid arthritis or osteoarthritis | 56,996 (42.0) | 11,137 (41.1) | 45,859 (42.3) | <.001 |
| Chronic kidney disease | 51,143 (37.7) | 11,432 (42.1) | 39,711 (36.6) | <.001 |
| Congestive heart failure | 36,512 (26.9) | 8,818 (32.5) | 27,694 (25.5) | <.001 |
| Depression | 31,881 (23.5) | 10,341 (38.1) | 21,540 (20.0) | <.001 |
| Acquired hypothyroidism | 31,857 (23.5) | 6,254 (23.1) | 25,603 (23.6) | 0.062 |
| Cataract | 29,053 (21.4) | 4,745 (17.5) | 24,308 (22.4) | <.001 |
SD = standard deviation. Top 10 comorbidities derived from list of 27 conditions present in Chronic Conditions Warehouse (CCW).
Table 2 displays the characteristics of the 450 practices, and the percentages of dually-enrolled and Medicare-only patients receiving care at practices with each characteristic. On average, there were 1.1 NP respondents per practice (range 1–4). Dually-enrolled patients were more likely to be seen in a practice that accepts Medicaid and has restricted SOP, and less likely to be seen in an urban practice. In terms of practice environment, dually-enrolled patients were more likely to be seen in the best practice environments, whereas Medicare-only patients were more likely to be seen in mixed or poor practice environments.
Table 2.
Characteristics of Primary Care Practices Where Dually-Enrolled and Medicare-Only Patients Receive Care
| Practice Characteristics | Patient Sample (N=135,648) |
Dually-Enrolled (n=27,126; 20.0%) |
Medicare-Only (n=108,522; 80.0%) |
p |
|---|---|---|---|---|
| Site specialty, n (%) | <.001 | |||
| Family practice | 18,360 (13.5) | 2,833 (10.4) | 15,527 (14.3) | |
| General practice | 21 (0.0) | 18 (0.1) | 39 (0.0) | |
| Geriatric medicine | 656 (0.5) | 123 (0.5) | 533 (0.5) | |
| Internal medicine | 16,861 (12.4) | 3,677 (13.6) | 13,814 (12.2) | |
| Multi-specialty | 99,732 (73.5) | 20,475 (75.5) | 79,257 (73.0) | |
| Accept Medicaid, n (%) | 79,910 (59.6) | 20,595 (77.6) | 59,315 (55.2) | <.001 |
| Accept new patients, n (%) | 128,598 (96.0) | 25,454 (95.9) | 103,144 (96.0) | 0.589 |
| Practice % dually-enrolled patients (mean, SD) | 20.0 (17.4) | 35.1 (24.2) | 16.2 (12.6) | <.001 |
| Urban, n (%) | 130,281 (96.0) | 25,429 (93.7) | 104,852 (96.6) | <.001 |
| Scope of practice, n (%) | <.001 | |||
| Reduced | 44,077 (32.5) | 6,956 (25.6) | 37,121 (34.2) | <.001 |
| Restricted | 91,571 (67.5) | 20,170 (74.4) | 74,401 (65.8) | |
| Daily practice volume, mean (SD) | 188.1 (195.1) | 160.4 (170.7) | 195.0 (200.1) | <.001 |
|
% NPs bill using their NPI,
mean (SD) |
62.1 (47.3) | 61.8 (47.3) | 62.2 (47.3) | 0.288 |
| Practice environment, n (%) | <.001 | |||
| Poor | 72,573 (53.5) | 14,355 (52.9) | 58,218 (53.7) | |
| Mixed | 39,055 (28.8) | 7,171 (26.4) | 31,884 (29.4) | |
| Best | 24,020 (17.7) | 5,600 (20.6) | 18,420 (17.0) |
SD= standard deviation, NP = nurse practitioner, NPI = National Provider Identifier. Reduced scope of practice includes California and Florida, Restricted scope of practice includes Pennsylvania and New Jersey. Practice environment classification designated by number of NP-PCOCQ subscales above median: 0–1 subscales = poor, 2–3 subscales: mixed, 4 subscales: best.
Table 3 displays the series of multilevel logistic regression models. In the unadjusted Model 1, the odds of dually-enrolled patients with chronic conditions being hospitalized were 85% higher than their Medicare-only counterparts (OR 1.85 95% CI [1.72, 2.00]. This disparity largely persisted in Model 2, adjusting for practice characteristics (OR 1.73, 95% CI [1.62, 1.86]) but narrowed in Model 3 adjusting for practice and patient characteristics (OR 1.33, 95% CI [1.25, 1.42]). In our final model, dually-enrolled patients still had significantly higher odds of being hospitalized (OR 1.48, 95% CI [1.37, 1.60]) Our models showed no main effect of NP practice environment; however, a significant interaction was found between dually-enrolled status and the best NP practice environments (OR 0.69, 95% CI [0.56, 0.85]), suggesting a differential influence of the NP practice environment on hospitalizations between dually-enrolled and Medicare-only individuals. The interaction term was not significant for mixed NP practice environments. In addition to practice environment, being in a practice that accepted new patients was associated with lower odds of hospitalization (OR 0.80, 95% CI [0.65, 0.99], while the presence of all but five of our included comorbidities were associated with a higher risk of hospitalizations. Patient race, patient sex, and all other practice-level characteristics were not significant.
Table 3:
Sequential modeling displaying effects of dually-enrolled status and the nurse practitioner practice environment on hospitalization disparities
| Model 1 Unadjusted OR [95% CI] |
Model 2 Adjusted for practice characteristics OR [95% CI] |
Model 3 Adjusted for patient and practice characteristics OR [95% CI] |
Model 4 Adjusted with interaction of practice environment and dually-enrolled OR [95% CI] |
|
|---|---|---|---|---|
| Hospitalization | ||||
| Dually-Enrolled | 1.85 [1.72, 2.00]** | 1.73 [1.60, 1.83]** | 1.33 [1.25, 1.42]** | 1.51 [1.40, 1.65]** |
| NP Practice Environment | -- | |||
| Mixed | 1.01 [0.86, 1.19] | 0.92 [0.81, 1.06] | 0.95 [0.84, 1.09] | |
| Best | 0.92 [0.78, 1.09] | 0.89 [0.77, 1.03] | 1.00 [0.87, 1.15] | |
| Dually-Enrolled X Practice Environment | -- | -- | -- | |
| Mixed | 0.86 [0.74, 1.00] | |||
| Best | 0.71 [0.58, 0.86]* |
Note. Odds ratios comparing odds of dually-enrolled patients being hospitalized, compared to Medicare-only patients. Reference group for practice environments is poor. Post-hoc tests conducted following significant interaction between Medicaid status & NP work environment. Patient characteristics include: age, sex, race, 28 chronic conditions (27 Elixhauser conditions and CAD); practice characteristics include practice type, whether they accept patients insured by Medicaid, whether they accept new patients, daily patient volume, percentage of patients dually-enrolled, whether NPs bill for their services, urban location, practice environment, and state.
p <0.01
p<.001
Post-hoc pairwise comparisons indicated that, as the NP practice environment improved, hospitalization disparities between dually-enrolled and Medicare-only individuals significantly narrowed. In poor practice environments, dually-enrolled patients had 48% higher odds of being hospitalized compared to Medicare-only patients (OR 1.48, 95% CI [1.37, 1.60]), while in mixed environments, dually-enrolled patients had 27% higher odds of being hospitalized (OR 1.27, 95% CI [1.12, 1.45]). However, in the best practice environments, hospitalization disparities between dually-enrolled and Medicare-only individuals became non-significant (OR 1.02, 95% CI [0.85, 1.23]). Table 4 displays the variation in the odds of dually-enrolled individuals being hospitalized across the three levels of practice environment.
Table 4:
Odds Ratios for All-Cause Hospitalizations Between Dually-Enrolled Patients and Medicare-Only Patients Across NP Practice Environment Levels
| OR | St. Err | p-value | 95% CI | |
|---|---|---|---|---|
| Dually-Enrolled Patients NP Practice Environment |
||||
| Poor | 1.48 | 0.06 | < .001 | 1.37, 1.60 |
| Mixed | 1.27 | 0.08 | < .001 | 1.12, 1.45 |
| Best | 1.02 | 0.10 | 0.432 | 0.85, 1.23 |
Reference group is Medicare-only beneficiaries. Post-hoc tests were conducted following significant interaction between Medicaid status & NP work environment in fully-adjusted model. Patient characteristics include: age, sex, race, 28 chronic conditions (27 Elixhauser conditions and CAD); practice characteristics include practice type, whether they accept patients insured by Medicaid, whether they accept new patients, daily patient volume, percentage of patients dually-enrolled, whether NPs bill for their services, urban location, practice environment, and state.
Finally, our sensitivity analyses found a main effect of practice environment on hospitalizations when limited to just dually-enrolled patients. Compared to those in poor NP practice environments, dually-enrolled individuals in mixed and best NP practice environments had just 82% (OR 0.82, 95% CI [0.67, 0.99]) and 70% (OR 0.70, 95% CI [0.58, 0.86]) of the odds of being hospitalized. However, when the sample was limited to Medicare-only patients, NP practice environment became non-significant (for mixed, OR 0.98, 95% CI [0.86, 1.11]; for best, OR 0.98, 95% CI [0.86, 1.12].
DISCUSSION
We found that, as the quality of the NP practice environment improved, hospitalization disparities between dually-enrolled and Medicare-only patients with two of the most common chronic conditions were significantly narrowed, and in the best cases became non-significant. This finding is consistent with those of other studies on the NP practice environment, which have noted that better NP practice environments are associated with improved chronic disease management, care quality, and provision of patient-centered care.16,19,20,24 Our findings add to a growing body of evidence on the role of NP organizational characteristics on reducing health disparities.14,24 To our knowledge, this study is the first to identify an association between the NP practice environment and disparities between dually-enrolled and Medicare-only patients.
Moreover, our sensitivity analyses found that dually-enrolled patients, but not Medicare-only patients, had lower odds of hospitalization when cared for in better NP practice environments. This may also explain the lack of a main effect for the NP practice environment in our main analyses, given that much of our sample was Medicare-only patients. While further studies are needed, these findings suggest that dually-enrolled individuals may be more sensitive to changes in the NP practice environment than traditional Medicare enrollees. Nurse practitioner-delivered care, with its focus on identifying and addressing the full spectrum of medical and social determinants of health, is highly aligned with the care needs of dually-enrolled patients.1,3,14,16,20,24 Improving the NP practice environment may therefore provide an opportunity for health systems to reduce the disparities faced by their dually-enrolled patients.
These findings have important clinical implications for dually-enrolled patients, and for the NPs and healthcare organizations who care for them. Dually-enrolled patients are simultaneously low-income and either disabled or older adults.1,3 Dually-enrolled patients also frequently live with multiple chronic conditions, while often lacking the social or economic resources necessary – such as accessible, affordable primary care – to manage these conditions.2,12 Primary care organizations and administrators may not fully understand or provide resources to support the unique role of NPs in managing chronic diseases through a holistic, nursing lens.14,17 In such environments, NPs may be unable to practice to the full extent of their knowledge, skills, and training, which may lead to health inequities and poorer ratings of care quality and patient-centered care.16,24 Because NPs are more likely to care for dually-enrolled patients, limited resources and support for NPs may lead to poorer outcomes and widen disparities for these patients.14
While improvements in the practice environment may represent a modifiable lever to address disparities amongst dually-enrolled individuals, significant health inequities amongst racially and socioeconomically marginalized populations must still be addressed. Multi-level solutions, including healthcare system reforms and community-level efforts, are necessary to address the complex health and social needs of dually-enrolled patients. At the practice level, healthcare organizations can invest in new models of care, prioritize population health, and partner with community organizations to address the health and social needs of complex patients such as dually-enrolled individuals. At the policy level, the removal of restrictive SOP policies has been associated with maintained or improved care quality and chronic disease management.15–17 At the community level, investments in the primary care workforce in health professional shortage areas – where dually-enrolled individuals disproportionately live – can improve the equitable allocation of healthcare resources.24
Limitations
Our study has important limitations. First, our findings are only generalizable to patients with either CAD or diabetes, and studies are needed to assess the influence of the NP practice environment on outcomes for other patient populations. Our cross-sectional design and inability to link NPs to individual patients also limit our ability to draw conclusions on causality. We address this limitation through our attribution methods, which have previously been found to reflect which providers our patient sample most frequently received their primary care from with relatively strong accuracy.12,39 Additionally, while evidence has demonstrated a relationship between state-level NP SOP and patient outcomes,13 none of our states designate full practice authority for NPs, and thus we were unable to explore the role of SOP. It is possible that other unmeasured factors, such as unobserved severity differences, practice-level care models, and specific community resources, may have influenced our findings. Future studies should take these multilevel factors into account when examining the role of the NP practice environment. Finally, though our survey response rate was low at 30%, this is within the expectation for survey research, and we validated this by sampling survey nonrespondents.47
Conclusions
Dually-enrolled individuals had up to 43% higher odds than their Medicare-only counterparts to experience a hospitalization. However, this disparity substantially narrowed when dually-enrolled individuals received care in supportive NP practice environments. Investing in improving the NP practice environment may be one step towards achieving equitable health outcomes for dually-enrolled individuals. More efforts by healthcare leaders and policymakers are needed to eliminate this disparity.
Supplementary Material
Acknowledgements
Funders were not involved in the conceptualization, design, or development of this study.
J.N was involved in conceptualization, design, statistical analyses, and writing and revising the manuscript. H.B was involved in design, statistical analyses, writing and revising the manuscript. A.M was involved in conceptualization, writing, and revising the manuscript. J.C was involved in conceptualization, design, and revising the manuscript. L.P was involved in conceptualization, writing, and revising of the manuscript. M.B.C was involved in conceptualization, design, statistical analyses, and revising the manuscript.
Disclosures:
This study was funded by the National Institute of Nursing Research (T32NR007104, PI: McHugh/Aiken/Lake; and R01NR014855, PI: McHugh/Aiken), the Robert Wood Johnson Foundation (PD10084376, PI: Nikpour), and the National Council of State Boards of Nursing (R101047, PI: Brooks Carthon/Poghosyan).
Research reported in this publication was supported by the National Institute Of Nursing Research of the National Institutes of Health under Award Number T32NR007104. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Footnotes
Conflict of Interest: The authors have no conflicts of interests to disclose.
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