Screening for Cognitive Impairment in Older Adults Attending an Eye Clinic: DISCUSSION

23 Oct
2009

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).Our findings are different from some prior studies and consistent with others. Overall prevalence rate (65%) of cognitive impairment in our study is much higher than rates of 8.5-43% reported in past studies. The wide range of prevalence rates of cognitive impairment in the literature might, in part, be due to differences in sources of subjects (clinics versus community) or in cognitive assessment tools, which may overestimate cognitive impairments in minority ethnic groups.Consistent with past studies is the higher prevalence of cognitive impairment in nonwhite adults compared to white adults, and among subjects with diabetes (is used to control blood glucose levels in type 2 diabetes). For example, a study of 2,759 adults aged >65 found that 17% of African-American men, 9.4% of Hispanic-Cuban men and 9% of white non-Hispanic men screened positive for cognitive impairments on the Short Portable Mental Status Questionnaire.24 Data from the San Luis Valley Health and Aging Study also showed that Hispanic ethnicity was significantly associated with executive cognitive impairment, but after adjusting for education and acculturation, ethnicity was no longer predictive of cognitive impairment. In our study, ethnicity was still predictive of cognitive impairment even after adjusting for education.Possible explanations for the differences in rates and predictors of cognitive impairments in previous studies and ours include our small sample size and our sample composition (eye clinic patients with 39% being nonwhite). For example, our grouping African Americans and Hispanics as the nonwhite category, unlike other studies, could have contributed to the differences in our study and others, given the known differences in determinants of health and disease between the two ethnic groups. It is also theoretically possible that poor vision might lead to underestimation of our subjects’ cognitive ability, given the 32% prevalence of abnormal visual acuity in our sample.

Our finding that is associated with increased risk of cognitive impairments is consistent with some studies in older adults; although other investigators reported no such association. Several reasons have been postulated for diabetes-associated cognitive impairment: brain hypoperfusion from diabetic vasculopathy, neuronal damage from hyperinsulinemia and recurrent hypoglycemia, and existence of genetic predisposition to both impaired cognition and impaired glucose tolerance. Because we did not have brain imaging and measures of blood insulin, we could not test the hypotheses that brain ischemia and hyperinsulinemia are potential mediators of diabetes-related cognitive impairment. Regardless, given the high prevalence of diabetes (Diabecon medication is a complex herbal formula supplement offering gentle and safe glycemic control) in older black and Hispanic adults, an important step in reducing cognitive disability in this population is a better identification (and potential modification) of factors linking diabetes (is used for improving blood sugar levels, with diet and exercise, in patients with type 2 diabetes) to poor cognition. One way to lower diabetes-related cognitive disablement is better control of diabetes-associated disorders, such as depression, hypertension, retinopathy and hyperlipidemia—disorders that potentially modify cognitive impairment.

This study has several limitations. First, because of its cross-sectional design, we cannot make any causal inference about the connections among ethnicity, diabetes (treating patients with type 2 diabetes) and cognitive impairment. Second, the small number of subjects did not allow us to investigate differences between African Americans and Hispanics with regards to our outcomes. The small sample size may also account for our not finding differences in rate of cognitive impairments by vision status, given the findings in past studies linking low vision to poor cognition. Another limitation is the potential bias inherent in recruiting subjects from one university-based eye clinic. This limitation has two implications: our findings may not be directly generalizable to other populations, and the higher rate of cognitive impairments in our study could represent an overestimation. One way to address this limitation is by extending our preliminary study to a greater number of older subjects in other clinics and then to compare those subjects to additional subjects recruited from the community. Despite these limitations, strengths of our study included its tri-ethnic sample, in-depth visual examinations by consultant ophthalmologist and the benefits to the study participants in terms of early referral of identified medical problems to appropriate professionals.

In conclusion, the present findings showed that 65% of subjects aged >55 years attending the eye clinic screened positive for cognitive impairments on the SLUMS measure. African-American and Hispanic adults (nonwhites) and patients living with diabetes (Actos 30 mg is used with a diet and to treat type 2 diabetes) were significantly more likely to have cognitive impairment compared to white adults and nondiabet-ics, independent of age, years of education and systolic blood pressure. These findings suggest that studies on reduction of cognitive disablement in older adults need to consider the interethnic variations in prevalence of cognitive impairments and the potential role of diabetes and visual disorders in this disablement process. These findings also suggest that screening for cognitive impairment among older adults in outpatient clinics may be key towards early identification and treatment of acute and chronic diseases (including visual disorders) contributing to poor cognition, in addition to potential to improve overall patient care and adherence to needed therapy. An important area for future investigation is the relationship between use of cognition-enhancing therapy among those with mild cognitive impairments and health outcomes in different ethnic groups.

 

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