Association Between Social Determinants of Health and Physical Function in the IBHPC study

Here are preliminary results from the first ancillary study using data from IBH-PC.

Association Between Social Determinants of Health and Perceived Physical Function in Adults with Comorbid Chronic Medical and Behavioral Problems: A Cross-sectional Analysis

Kathleen Whitbread MD, Benjamin Littenberg MD

Background: Patients with multiple chronic medical and behavioral health issues often perceive a lower health-related quality of life, but little research explored the association between socioeconomic factors and physical health.  Social determinants of health (SDH) differ from traditional socioeconomic factors by specifically addressing daily challenges such as food, housing and income insecurity. We sought to describe the association of SDH with physical function in a chronically ill primary care population.

Methods: This is a cross-sectional observational study of 154 randomly selected adults from the Integrating Behavioral Health and Primary Care for Comorbid Behavioral and Medical Problems study. Subjects had at least one chronic medical illness and one behavioral health need. An SDH score was calculated for each subject based on 4 questions about their ability to meet their basic daily needs including food, housing and other expenses. Physical function was measured by the 12-item Duke Activity Status Index (DASI) which has been validated against exercise testing with measurement of peak oxygen uptake.  Race was dichotomized as “White” vs. all others and Low Income was defined as self-reported annual household income <$30,000. We used nonparametric robust linear regression to assess the relationship between DASI, SDH, and other social factors.

Results: Subjects without any SDH challenges were found to have a mean DASI score of 31.4 METs (95% confidence interval [28.3, 34.4]), compared to subjects identified as having moderate (21.8 [16.0, 27.6]) or severe (19.1 [12.6, 25.7]), a significant trend (P<0.001). Race and low income were significantly associated with both SDH score and DASI and were retained in multivariate linear regression to control for possible confounding. Adjusting for race and low income reduces the strength of association of SDH with DASI, rendering it non-significant, and demonstrating confounding.

Conclusion: There is an association between SDH and physical function in patients with chronic medical conditions and behavioral health needs. However, other social variables (e.g., income and race) confound the relationship between DASI and SDH, making determination of the causal pathway problematic. Does poor function lead to social challenges or vice versa? Unlike other socioeconomic variables, however, housing and food insecurity can be directly addressed in the primary care setting.  Although there were multiple limitations to this study including a small number of subjects and lack of several predictors including age, this study suggests that such efforts may be valuable. Social determinants of health are potentially modifiable risk factors for poor physical function in the chronically ill.

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Dr. Whitbread, an Internal Medicine Resident at the University of Vermont Medical Center, led the study and presented these preliminary results at Medical Grand Rounds in Burlington on May 25, 2018. As more baseline data come in, the analysis will be expanded and updated.