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.
Research Question 1: How does access to medical services affect the quality of life after a diagnosis of dementia. SES factors like age, geographical location, wealth, education, and income could all affect the types of services available to individuals, and the same factors could affect the quality of life after a dementia diagnosis. It might be useful to control for SES factors when assessing the relationship between medical services and quality of life with dementia. It would then be interesting to stratify different race/ethnicities to see if the effect is different between the groups.
Research Question 2: Does geographical distance to work effect the amount of exercise that an individual gets? Individuals who live far away from work will likely need to take some form of motorized transportation rather than walking or biking. In this scenario, SES factors like income or age could effect the relationship. For example, someone with a high income or an advanced age may own a personal car and be able to park in a spot at home and at work, thus resulting in minimal exercise. Another individual with low income or a younger age may, by choice or necessity, decide to find alternative methods like biking or walking from bus stops, thus increasing exercise. In this scenario, SES factors are modifying the relationship between distance and exercise.
Research Question 3: To whom does our current research in dementia apply? Dementia research is time intensive and recruitment/retainment of study participants is difficult. SES factors may affect the ability of an individual to be identified, recruited or retained in a study, thus leading to the study results that are less applicable to some groups. In this case, SES is mediating the relationship between research studies and the groups to which the results apply.
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.
Exercise is thought to be related to the development of dementia, and neighborhood structure has been shown to affect the amount of exercise that individuals will get, often over long periods of time. For example, someone living in an urban neighborhood like San Francisco is more likely to walk to a nearby store, or bike across town to get to work. This is partially due to the proximity of stores as well as it being harder on average for individuals to keep a car and find/afford parking. Elsewhere, like in cities of the California Central Valley, neighborhoods are spread far apart, with residential areas often spanning several square miles before a store can be found. It is expected that residents will have a car and use it to get most places, thus reducing the need to go out and walk. A question of interest thus arises: How does geographical location affect the relationship between exercise and dementia?
Contextual variables derived from geographical location may include: average distance for neighborhood residents between home and work, home and food, or availability of local gyms or even culture around bicycling (example, in my home town of Modesto, very few individuals bike, and there is even a slight stigma around biking as it is seen as a low income mode of transportation!) Most of these variable could be viewed as factors that lead to different levels of exercise behaviors in individuals that then could affect the development of dementia. In this relationship, exercise could be considered a mediator between geographical location and dementia. Additionally, the effect of geographical location on exercise could by modified by factors like SES or social group.