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.
A high level of participant enrollment was achieved in the CHCs. The calculation of a standard response rate, however, is not possible, due to the recruitment strategies employed by the interviewers. In addition to randomly approaching single individuals, some interviewers found that a successful means of recruitment was to speak to an entire CHC lobby at once, explaining the study and its eligibility requirements, then enrolling the resulting volunteers. Moreover, we found that there were various routes by which potential participants came to the interviewer already prescreened for interest and eligibility: 1) through word-of-mouth referrals from previous participants; 2) through referrals from the CHC receptionists or medical staff; and 3) from volunteers who sought out the interviewer in response to seeing posters, flyers, brochures or even articles and advertisements placed in local newspapers by some CHCs.
This study was approved by the institutional review boards at Vanderbilt University and Meharry Medical College. All participants provided written informed consent and (since April 14, 2003) a signed Health Insurance Portability and Accountability Act (HIPAA) authorization.
U.S. cancer statistics document higher incidence rates of most forms of cancer, including cancers of the oral cavity, pharynx, esophagus, stomach, colon, lung, cervix, kidney, liver and prostate, among African Americans than whites, yet reasons for the racial disparity are poorly understood. Blacks also experience poorer survival than whites for nearly all forms of cancer (treating breast cancer that has spread to other sites in the body), so that the disparities tend to be even greater for mortality than for incidence. Mortality rates for both stroke and heart disease are also higher among blacks than whites in the United States.
Our findings can be summarized as follows. In our study sample of 100 community-dwelling subjects aged >55 years attending a university-based eye clinic, 65 subjects screened positive for cognitive impairments on the SLUMS. African-American and Hispanic adults (nonwhites) were significantly more likely to have cognitive impairment compared to white adults, independent of age, years of education and systolic blood pressure. Subjects with diabetes also had increased odds of cognitive impairment even after adjusting for relevant confounders, including ethnicity and visual acuity. After adjustments were made for presence of diabetes, ethnicity was no longer significantly predictive of cognitive impairment, indicating a possible mediating effect of diabetes (Prandin canadian used in addition to diet and exercise to lower blood sugar in adults) on the association between nonwhite ethnicity and increased likelihood of cognitive impairments. There was a nonsignificant trend between visual acuity impairment and cognitive impairment (p=0.059).
Figure 1 shows the frequency of subjects by performance on the SLUMS measure. Thirty-five subjects had normal scores. Sixty-five subjects had scores in the cognitive impairment range: 46 with mild cognitive impairment and 19 with severe impairment (possible dementia).
Following approval from the University of Texas Medical Branch (UTMB) institutional review board, we collected social, demographic and health information from 100 consecutive Hispanic, African-American and white adults, aged >55, who came to receive ophthalmologic care at the UTMB Eye Center. Patients included in the study had no history of dementia, were able to give informed consent for the interviews and physical examination, and were able to communicate in English or Spanish. The eye examination was done by a board-certified ophthalmologist. Patients with significant cognitive, physical and emotional disorders were referred to appropriate professionals for further management.
The data collection was performed over a period of eight months (November 2003 to June 2004). In addition to sociodemographic and medical information and using standardized questionnaires, we collected information on physical activity level and cognition. All participants also had a comprehensive eye examination as well as blood pressure measurements. The assessments lasted approximately one hour. Interviews were done in English or Spanish, depending on the preferences of participants. The bilingual interviewers were thoroughly trained in the administration and scoring of the questionnaires.