Sorry for the delay..
1. Give an example of a research question for investigating racial/ethnic health disparities where: [1] SES is a confounder; [2] SES is an effect modifier; [3] SES is a mediator. Briefly discuss the interpretations/implications of each approach as it relates to understanding health disparities by race/ethnicity.
1. SES as a confounder: The diagnosis of sarcoidosis can be challenging and elusive, especially since it requires a tissue biopsy and often times, expert referral. We and others have found that African Americans have a longer lead time between symptom onset and official diagnosis. A question could be whether this is due to having decreased access to referral experts, i.e. pulmonologists, would decrease the lead time between when sarcoidosis patients start to have symptoms and when they are diagnosed. An observational study to address this could look gather data that determines the duration of time between when someone starts to have symptoms and when they are diagnosed and relate this to the number of pulmonologists per square mile in their neighborhood using census tract data. However, SES could be a confounder because areas with higher densities of pulmonologist specialists could also be areas where patients have higher incomes, and higher SES may also affect how feasible it is for patients to see a specialist (e.g. if they cannot get time off work to be seen). If SES is not controlled for, associations between having greater number of providers and decreased time to diagnosis could be found, that are actually due to effects of SES.
2. SES as an effect modifier: African Americans have also been found to have overall worse outcomes after being diagnosed with sarcoidosis, including more severe symptoms and more aggressive multi-organ disease. The treatments that are used for sarcoidosis include corticosteroids like prednisone and non-steroid agents like methotrexate. A question could be how we could improve treatment strategies for these patients. A main issue with this could be that the differences in outcomes with these medications is due to SES status. For example, those with lower SES have more limited resources to get frequent lab testing required for these medications, therefore they don’t adhere to them or have toxicities. However, this could impact African Americans more than Whites due to other factors that affect their access to lab testing in lower income patients. Therefore, SES could be an effect modifier for treatment response AND race could be another effect modifier, such that it is lower SES that affects treatment, and on top of that, African Americans also have worse outcomes if they have lower SES as compared to Whites.
3. SES as a mediator: Sarcoidosis can cause significant symptom severity that can be quite debilitating and lead to loss of work and income. Similarly, once patients lose their jobs, then their symptoms related to the disease, e.g. fatigue, anxiety, and subjective experience of shortness of breath, can worsen. Pulmonary rehabilitation is a program that helps improve function and overall symptoms in patients with respiratory compromise. One of the potential reasons for the improvement in symptoms is because patients are able to improve their respiratory symptoms and return to work, which can then reduce their overall stress and impact on their life. In this way, a patient’s SES status (e.g. ability to work and earn a living) could be mediating part of the improvements they are having from pulmonary rehabilitation. In African American patients, there could a difference in response since improvements in earning and ability to find a job may not be as easy as it is for White patients (e.g., once an African American loses a job because of disability, it may be harder to find another one because of systemic bias). This would be an important issue to assess when determining the effects of programs like pulmonary rehabilitation.
2. Describe a potential effect modifier, mediator, or contextual variable (for definition of contextual variable, see Diez-Roux reading) for an association of interest to you and relevant to health disparities. For example, for investigating the association between education and hypertension, I might be interested in evaluating whether the association between years of education and hypertension is different for Black men than for White men. Describe how you would study whether this relationship exists.
I am interested in understanding why African Americans have worse outcomes in sarcoidosis than Whites. Sarcoidosis is more common in African Americans with a higher incidence and prevalence.1-3 Unfortunately African Americans have been consistently shown to have worse outcomes with respect to disease severity and mortality.4 The disease has many complexities. It has an unknown cause but is characterized by non-necrotizing granulomas. The strong immune basis of the disease has led to studies involving the important immune cells that are driving this disease. It is thought that immune cells are reacting to antigens (proteins) in the environment, that are then triggering the inflammation and causing it to not resolve. One issue that I raised above is the fact that African Americans have longer lead times between onset of symptoms and diagnosis. Later diagnoses can mean that African Americans have disease for longer that has been untreated and therefore more severe by the time the disease is recognized. This could lead to longer periods of unchecked inflammation that is harder to treat and what the cause of that is. The cause of increased lead times in African Americans could be SES or access to healthcare. I would want to enroll patients and determine their time from symptom onset to diagnosis and compare Whites to Blacks. I could then see if other factors such as insurance/physician access or SES are mediating the effects of the differences in Race for lead time in sarcoidosis diagnosis.
3. Respond to one other person's post on the forum with a comment or suggestion.
Please see Alison Dedent’s post.
1. Siltzbach LE. CURRENT THOUGHTS ON THE EPIDEMIOLOGY AND ETIOLOGY OF SARCOIDOSIS. The American journal of medicine 1965;39:361-8.
2. Rybicki BA, Major M, Popovich J, Jr., Maliarik MJ, Iannuzzi MC. Racial differences in sarcoidosis incidence: a 5-year study in a health maintenance organization. American journal of epidemiology 1997;145:234-41.
3. Nagai S, Shigematsu M, Hamada K, Izumi T. Clinical courses and prognoses of pulmonary sarcoidosis. Current opinion in pulmonary medicine 1999;5:293-8.
4. Mirsaeidi M, Machado RF, Schraufnagel D, Sweiss NJ, Baughman RP. Racial difference in sarcoidosis mortality in the United States. Chest 2015;147:438-49.