Discussion
This indepth examination of multidimensional SDoH in a low-income, non-Hispanic black Medicaid population highlights the important role that SDoH play in impacting adherence to diabetic retinopathy examinations. Even after eliminating cost as a barrier, one of the most commonly reported reasons for not receiving eye care,10 24 several SDoH factors emerged as significant predictors of adherence. Our two main findings are that (1) regular healthcare providers, such as primary care doctors, family care doctors, or general practitioners, have an important role in promoting adherence to diabetic retinopathy examinations, and that (2) patients who have poor housing conditions can have decreased adherence to diabetic retinopathy examinations. These associations suggest possible _targets for hospital or community-based interventions to promote diabetic retinopathy examinations.
The rates of diabetic retinopathy examinations in our population, 48% using the biennial definition and 17% using the annual definition, are largely consistent with other reported rates in the literature, which range from 15% to 77%.6–8 It is as high as 70%–77% by national surveys and integrated healthcare systems.24–26 In the Medicare population, adherence ranges from 25% to 60% when defined as one eye examination in a 15-month period.6 7 9 In a predominantly low-income African American population with diabetes in Alabama, diabetic retinopathy examination screening rate was about 30%.27 In an urban Hispanic population with diabetes in Los Angeles, 35% had eye examinations within the previous 12 months.28 In an urban Medicaid population in the mid-Atlantic, similar to our study, the adherence rate was 46% for annual examinations. The lowest rates of adherence were reported by Benoit and colleagues8 using the IBM MarketScan Research Database. The authors report only 15% of patients with type 2 diabetes without diabetic retinopathy and 51% with diabetic retinopathy met the annual or biennial eye examination recommendation, compared with 42% and 58%, respectively, in our population. It is difficult to compare rates of eye examinations between studies due to differences in the underlying population and varying definitions of ‘adherence’. What is clear, however, is that the rate of diabetic retinopathy examinations for most populations, including ours, continue to fall short of the Healthy People 2030 goal of 67.6%.29 The Healthy People initiative is a set of science-based objectives released by the US Department of Health and Human Services designed to guide national health promotion by setting _targets to monitor and motivate progress.30
Evaluating and addressing SDoH are potential means to improve adherence to diabetic retinopathy examinations. Our study found decreased adherence in those without regular healthcare providers, who had poor housing conditions, and were living with children. Regular healthcare providers, including primary care physicians, play a central role in coordination of care and promoting adherence to diabetes guidelines, including diabetic retinopathy examinations.31 Not surprisingly, patients who responded that they “have a regular doctor that [they] see” had increased odds of being adherent to diabetic retinopathy examinations, using both the primary outcome and in the sensitivity analyses. Strategies aimed at decreasing barriers in the referral process to eye care and improving communication between ophthalmologists and primary care physicians are effective in increasing eye examination rates.32 33 Future hospital-based interventions could focus on further improving this connection.
Having poor housing conditions has not been previously associated with adherence to diabetic eye examinations. Multiple mechanisms could explain this association. Poor housing conditions could be a general indicator of poverty. Living in overcrowded conditions is a precursor to homelessness and can make it difficult to attend preventive services and perform self-care.13 18 19 The physical aspects of where people live, or the built environment, can influence physical activity, walkability, and transportation to access healthcare.34 35 The association of poor housing conditions with adherence to diabetic eye examinations adds to the expanding literature on the critical role of housing in health. It is unknown why poor housing condition was not associated with adherence in sensitivity analyses. In the univariate model, poor housing conditions had a borderline association (OR 0.72, 95% CI 0.47 to 1.10, p=0.13) with decreased adherence to eye examinations that was not statistically significant. It could be that poor housing is an important SDoH but not the most important one, or that there could be fluctuations in the data due to sample size. Lastly, living with children also showed decreased odds of eye examinations in the sensitivity analyses. The cohort living with children in general were 7.5 years younger than those who were not. One possible explanation is that this cohort had added caregiving responsibilities that interfered with healthy behaviors and follow-up.36
It is unknown why the other SDoH were not associated with adherence to diabetic retinopathy examinations. For example, not having a high school degree has been previously associated with increased non-adherence to diabetic retinopathy examination, but not in our study.37 It could be that in the context of multiple SDoH, structural determinants including education are not as significant as intermediary determinants. Another possibility could be a combination of the sample size and the number of patients with social adversities. In this cohort, 34% of the population had very few social risks and were largely employed; only 12% had the most social risks and were unemployed, and the majority of patients fell somewhere in between.20 Financial strain can impact adherence to diabetic retinopathy examination but our study did not find this association.24 It could also be that having insurance supersedes other measures of financial strain by eliminating the financial barrier to diabetic retinopathy examinations. We also found a lower adherence among younger male patients with type 2 diabetes, which is consistent with other studies.25 37 Other studies have found an association of race/ethnicity with adherence to diabetic retinopathy examinations, while our study did not.11 37 38 A key difference is that our study was in a largely homogenous population of 91% black persons; thus, there was not enough heterogeneity to delineate the role of race/ethnicity. In addition, race/ethnicity is often used as a surrogate for socioeconomic status, whereas this is a relatively homogenous group of low-income adults.
Although most experts agree that SDoH underlie health outcomes, there is little consensus on how they should be assessed and incorporated into routine clinical care. There is a wide variety of published tools and guidelines that emphasize different aspects of SDoH.39–42 There is no consensus on a specific set of factors defining SDoH and there is a lack of standardized nomenclature across the field, but what is clear is that SDoH is a multidimensional construct.12 13 43 44 Existing literature examining SDoH in diabetic retinopathy care has predominantly focused on socioeconomic status and access to healthcare and has not assessed other dimensions of SDoH. By evaluating multiple determinants, even in our brief 10 min survey, we were able to highlight novel associations between SDoH and adherence to diabetic retinopathy examinations. An evaluation of multidimensional SDoH could be incorporated into routine clinical diabetic retinopathy examinations. For example, initial screening questions could include elements such as not having a primary care physician or poor housing conditions that subsequently lead into further questions and evaluations. Ultimately, addressing these SDoH and connecting patients to needed services could lead to improved patient adherence to eye examinations. More work is needed to identify the precise list of multidimensional SDoH that are relevant for adherence to diabetic retinopathy examinations and the best methodology to screen for them.
This study has a number of limitations. The results of this study are not generalizable as the cohort is not a representative sample of Medicaid beneficiaries. We enrolled a group of individuals who were already seeking treatment. The Washington, DC Medicaid program has an expansive eligibility criteria and covered services; thus, the enrollees in the Washington, DC Medicaid program might not be reflective of populations enrolled in other state Medicaid programs. The accuracy of our definition of type 2 diabetes is unknown. It is possible that our population also erroneously included some individuals with type 1 diabetes, although only 8% of our population are dual-coded with type 1 diabetes. Individuals with type 1 diabetes are also recommended to receive screening diabetic eye examinations, but the guidelines are different from those with type 2 diabetes.4 Administrative claims data are not always accurate for clinical diagnoses and examinations since coding practices may vary by healthcare provider. Although we used previously published cohort and outcome definitions, we could be overestimating adherence to eye examinations if dilation was not performed at these office visits. The definition of adherence also varies in the published literature. Recommendations for frequency of eye examinations depend on the severity of retinopathy and presence of diabetic macular edema, but that level of granularity is not reliably captured in the claims data used in this analysis.45 Thus, the definitions of adherence used for this study reflect the most general recommendations of examinations every 1–2 years.4 Altering the definition of compliance can drastically change associations, but we were able to show robust findings even in sensitivity analyses.9 Lastly, knowledge of diabetic retinopathy and visual impairment from eye disease improves adherence to eye examinations, but these ophthalmic-specific characteristics were not measured in this study and could be confounders.24
In conclusion, evaluating and addressing multidimensional SDoH are critical components of promoting adherence to diabetic retinopathy examinations and improving health outcomes. Our study confirms the previous finding that having a regular provider impacts adherence to diabetic retinopathy examinations and has identified poor housing conditions as a novel association that warrants further investigation. Future interventions can focus on these important determinants to improve adherence and eliminate health disparities in diabetic retinopathy care.