Establishing a Cohort to Investigate Health Disparities: DISCUSSION

27 Oct
2009

Despite higher rates of morbidity and mortality from many cancers and nonmalignant chronic diseases, African Americans have been poorly represented in epidemiologic studies. One impediment to inclusion has been the tendency of studies to sample from populations where African Americans have limited representation. Moreover, African Americans have often been reluctant to participate because of mistrust resulting from the historical exploitation of blacks in medical research studies, the belief that medical research is not carried out ethically, and the view that chronic disease prevention is a low priority in the context of more immediate socioeconomic and psychosocial pressures.

We sought various means of overcoming these barriers. First, we identified a geographic area where African Americans are well represented, and within those areas, identified CHCs as a means of gaining access to a portion of that population. Second, we established strong ties between the study team and the CHC network in the south, who could partner with the study and effectively promote it as a credible and worthwhile endeavor. For the study team, this involves visits to CHCs across the south, meetings with and presentations to CHC staff, attendance at regional and national CHC conferences to meet CHC administrators and promote the study, and assigning a study field manager to each CHC to act as a day-to-day liaison. Third, at the CHCs, we recruit subjects face to face, and our study interviewers are not viewed by potential participants as “outsiders” to their community. Interviewers are hired as employees of the CHC, come from the local community, tend to be racially concordant with the patient population and are often motivated by community-driven interests. Some of the study interviewers are long-time employees of the CHC and therefore are already known and trusted figures to the patient population. Finally, our study materials were designed to be culturally sensitive and comfortable for a wide range of educational levels, as well as to impart a clear message about the relevance of this study to the health of southerners—African Americans in particular. cheap generic sildenafil

These strategies are very labor-intensive. In particular, enrolling cohort members at CHCs across the south is a complex operation, and the management of a strict scientific protocol at numerous autonomous organizations (many with multiple clinics functioning as recruitment sites) requires a high level of coordination. The recruitment success we have achieved, however, demonstrates the value of the CHC relationships. On a practical level, working within the CHC also facilitates the collection of biologic specimens, particularly blood. Most CHCs have on-site laboratories and phlebotomists, and it is often possible to have the SCCS blood taken jointly with blood already required for physician-ordered tests, increasing donation rates. Being present within CHCs also allows access to medical records, and it facilitates in-person interviewing, which is preferable to phone or self-administered surveys. Another important benefit of this approach is the drawing of CHCs into the research arena, with the potential for this experience to promote a lasting interest and ongoing participation in public health research projects.

Specific challenges associated with CHC-based field work should also be discussed. Our experience indicates that recruitment at an average CHC abates within 12 months due to the depletion of the pool of eligible study participants. Seasonal fluctuations in patient attendance at the CHCs also affect subject enrollment, with low points occurring during the winter holiday season and during the summer months. Some CHCs have sufficiently large patient populations to have recruitment extend for a number of years and to weather slow periods of patient flow, but this is uncommon. The inclusion of CHCs from rural areas is a particular challenge, as they can be very small in size; lack support, such as internet connectivity and conveniently timed Federal Express service for biospecimen shipments; and involve multiple geographically dispersed sites (which makes efficient field work difficult if interviewers need to travel from site to site). levitra plus

CHC patients are not representative of the general southern population. However, one of our goals was to reach persons of low SES from rural and urban areas in the south who would be extremely difficult to reach by other means. Twenty-two percent of African-American adults in our current enrollment states live below the poverty level. Therefore, while not being broadly representative of southern blacks, CHCs capture a group that makes up a sizeable minority of that population and a group that is at especially high risk for premature morbidity and mortality. Another advantage of this recruitment strategy is the enrollment of white participants who have similar incomes and educational backgrounds. This helps reduce some of the confounding by socioeconomic status that is present in most studies that attempt to enroll large numbers of blacks and whites. Historically, through investigator-defined study bases and through participant self-selection, prospective cohort study members typically represent a higher SES stratum than the general population, with exposure information corresponding to that stratum. The SCCS has the potential to extend the usefulness of the collective body of cohort data past this boundary by adding information from a different, understudied population.

Starting in 2005, a segment of the SCCS cohort will be drawn from a separate, population-based sample and thus provide additional participants that span middle- and upper-income levels. In total, the SCCS cohort will cover the broad SES spectrum to enhance variability in exposures, distinguish effects of race from economic level and therefore aid in drawing eti-ologic inferences. Our preliminary data suggest that we already have a more than adequate range of important exposures within the current CHC-enrolled cohort to conduct powerful statistical analyses. It remains to be seen how different the exposures will be between the CHC-enrolled and the population-enrolled portions of the cohort, but all statistical analyses will be stratified by enrollment type.
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The use of different modes of data collection (in-person interviews versus self-administered questionnaires) for the CHC-enrolled and general population-enrolled segments of the cohort, respectively, raises the issue of possible systematic differences in reporting answers between the two groups. Steps will be taken to minimize differences between the two surveys. For example, intelligent character recognition technology will allow participants to answer most questions on the paper form the same way they could during an interview (i.e., writing in their numeric answers rather than having to choose from preassigned categories). While there is little published data about the relative performance of these two methods among African Americans specifically, we expect: 1) more missing data from the self-administered questionnaire, but 2) fairly comparable reporting of health indices and health-related behavior. Also, as mentioned above, our statistical analyses will be conducted separately for these two groups to examine any effect modification before the groups would be combined.

With regard to follow-up, participant-identifying information obtained at baseline will enable nearly complete mortality follow-up through the National Death Index and other sources, even if participants move from the south. Through state registries, we will also be able to ascertain information on inci dent cancer diagnoses (Nolvadex canadian is an anti-estrogen used to treat or prevent breast cancer), although reporting lags will result in over two-year delays in case identification in some states. We anticipate that active follow-up will be especially challenging due to the low education and income levels of many participants.

In summary, the SCCS is an ambitious undertaking, seeking to enroll large numbers of adults from segments of the American population underrepre-sented in previous epidemiologic research. The success of the study to date derives largely from the utility of the CHC system for the recruitment of African-American and low-income participants. We are assembling a unique cohort of southerners and oversampling African Americans to investigate the racial disparities that are currently seen in cancer (treating endometriosis, symptoms of fibrocystic breast disease, orgiant hives) risk and other chronic disease outcomes. Biospeci-men collection for the SCCS has been exceptionally successful, and the resulting repository will aid us in investigating molecular markers for cancer (Eulexin drug is used along with drugs such as Lupron to treat prostate cancer) and other diseases, and in exploring gene-environment and gene-gene interactions. We anticipate that the future results of the SCCS will be valuable for assessing risk factors and for developing prevention measures aimed at cancer (reducing the number of painful episodes and blood transfusions needed by adults with sickle cell anemia experiencing recurrent episodes associated) and other serious diseases, especially among African Americans.

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