Financial Hardship and Risk of Incident Diabetic Kidney Disease

Approximately 30.3 million individuals in the United States are affected by diabetes; since the 1980s, there has been a rise in the prevalence of diabetes, accompanied by a rise in diabetic kidney disease (DKD). DKD affects ~40% of those with diabetes, putting them at increased risk of cardiovascular disease and progression to end-stage kidney disease. There are also associations between DKD and increased healthcare costs and risk of mortality.

Growing evidence suggests the role of social determinants in diabetes outcomes. Social determinants of health include the conditions in which individuals are born, grow, live, work, and age. Those conditions exacerbate health disparities at global, national, local, and individual levels, and impact individuals’ socioeconomic status. The standard metrics of socioeconomic status, including education, occupation, and income, may be insufficient to capture the true burden some individuals are experiencing.

Financial hardship is a measure that accounts for material conditions, psychological response, and coping behaviors related to interaction with the healthcare system. Associations between financial hardship and poor health are well recognized. However, there are few data available on the association between financial hardship and incident diabetic kidney disease (DKD) in the United States.

Timothy R. Corwin and colleagues conducted a study designed to assess the longitudinal relationship between financial hardship and incident DKD among older adults with diabetes. The researchers sought to test the hypothesis that there is a positive longitudinal relationship between financial hardship and incident DKD among older adults in the United States with diabetes. The second hypothesis was that there is a positive association between positive, negative, and persistent financial hardship change and incident DKD in adults with diabetes in the United States. Results were reported online in BMC Nephrology [doi.org/10.1186/s12882-021-02373-3].

Using four waves of data (2006-2012) from the Health and Retirement study, a national longitudinal cohort, the analyses included 2735 adults ≥50 years of age with diabetes and no DKD. The primary outcome of interest was incident DKD based on the question: Has your diabetes caused you to have trouble with your kidneys or protein in your urine?

Based on validated surveys, financial hardship was defined as: (1) difficulty paying bills; (2) food insecurity; and (3) cost-related medication nonadherence. Using all three measures, the researchers constructed a dichotomous financial hardship variable (0 vs 1 or more). The variable was generated by coding all yes responses as 1 and no responses as 0. Financial hardship was defined as a score of ≥1. In addition, a 4-category change in financial hardship experience was created for those who answered the financial hardship question during the follow-up interview as: (1) those who reported no financial hardship in both interviews were categorized as no financial hardship; (2) those who reported financial hardship in both interviews were categorized as persistent financial hardship; (3) those who reported financial hardship in the first interview and no financial hardship in the second interview were categorized as positive financial hardship change; and (4) those who reported no financial hardship in the first interview and financial hardship in the second interview were categorized as negative financial hardship change.

After adjusting for demographics, socioeconomic status, and comorbidities, the association between financial hardship, change in financial hardship experience, and incident DKD was estimated using Cox regression models.

Median follow-up was 4.1 years (10,686 person-years of follow-up). A total of 347 adults developed incident DKD. Mean age in the overall cohort was 68.1 years; mean age of those without financial hardship (n=1648) was 69.8 years; in those with financial hardship (n=1087), mean age was 65.4 years. Compared with those without financial hardship, adults in the financial hardship group were more likely to be female, of ethnic minority, have less education, and  have a low household income.

During follow-up, the rate of incident DKD was higher in those with versus those without financial hardship (4.12 per 1000 person-years vs 27 per 1000 person-years). Following adjustment, the likelihood of developing incident DKD was significantly increased in those with financial hardship compared with those without financial hardship (hazard ratio [HR], 1.32; 95% confidence interval [CI], 1.04-1.68). Persistent financial hardship and negative financial hardship  were associated with incident DKD compared with no financial hardship experience (adjusted HRs, 1.52; 95% CI, 1.06-2.18 and 1.54; 95% CI, 1.02-2.33, respectively).

Positive financial hardship was not statistically significant in unadjusted and adjusted models (adjusted HR, 0.89; 95% CI, 0.55-1.46). Independent of other financial hardship measures, cost-related medication nonadherence was associated with incident DKD (adjusted HR, 1.43; 95% CI, 1.07-1.93).

The researchers cited some limitations to the findings, including substantial heterogeneity in the literature in measures of financial hardship, limiting the ability to compare the findings with other studies; using self-report as the basis of the presence of diabetes and DKD, perhaps underestimating the prevalence of DKD; the possibility of residual confounders; and restricting the study population to older adults, limiting the ability to generalize the findings to younger adults with diabetes.

In conclusion, the researchers said, “In a longitudinal cohort of older US adults we show that compared with individuals without financial hardship, individuals with financial hardship experience were significantly more likely to develop DKD. In particular, individuals reporting persistent financial hardship had a higher probability of patient reported incident DKD while individuals reporting negative financial hardship change may be at risk of incident DKD. Our study findings suggest cost-related medication nonadherence may be an important target for future intervention studies to mitigate adverse outcomes. Future studies are needed to explore factors not included in this study that may explain the relationship between financial hardship and incident DKD.”

Takeaway Points

1. Researchers reported results of an analysis of data from a national longitudinal cohort of adults in the United States with diabetes to examine the longitudinal relationship between financial hardship and incident diabetic kidney disease (DKD) in that patient population.
2. Incident DKD was higher among those with versus those without financial hardship: 41.2 per 1000 person-years versus 27 per 1000 person-years. In adjusted analysis, the likelihood of developing DKD was significantly increased in those with financial hardship compared with those without financial hardship.
3. Persistent financial hardship and negative financial hardship change were associated with incident DKD compared with no financial hardship experience.