Published research has shown that type 2 diabetes is associated with about a twofold greater risk of dementia among older adults, but it is unclear if the risk of dementia for people with diabetes varies across racial and ethnic groups. “Over the last 10 years, much has been learned about the connection between type 2 diabetes and dementia risk,” says Rachel A. Whitmer, PhD. “Rates of both of these conditions continue to rise as the population ages and as there continues to be growing ethnic diversity among older patients. Because type 2 diabetes increases the risk of dementia, it’s important to understand the risk of dementia among older adults with type 2 diabetes who are from diverse racial and ethnic backgrounds.”

A national public health goal has been set forth to eliminate health disparities. This makes it increasingly important to understand racial and ethnic differences in diabetes-related complications, including dementia, among older adults. Studies have reported that the prevalence of dementia is higher among African Americans and Caribbean Hispanics, lower among Japanese Americans, and similar among Native Americans and Mexican Americans when compared with Caucasians. However, knowledge about racial and ethnic differences in dementia risk has not been thoroughly investigated among people with type 2 diabetes.

Exploring Racial & Ethnic Differences

In Diabetes Care, Dr. Whitmer and colleagues had a study published that examined if there are racial and ethnic differences in the 10-year incidence of dementia among individuals with type 2 diabetes. The study analyzed more than 22,000 culturally diverse patients with diabetes aged 60 and older who did not have preexisting dementia and were part of the Kaiser Permanente Northern California (KPNC) Diabetes Registry. “Inclusion of our study patients in the KPNC Diabetes Registry is important,” says Dr. Whitmer. “This provided an excellent setting to examine racial and ethnic differences because health plan members had uniform access to care.”

Overall, dementia was diagnosed in 17.1% of patients involved in the study. Dementia incidence densities were highest among Native Americans and African Americans and lowest among Asians (Table 1). In addition, consistent patterns were seen after adjusting for age, sex, and level of education in Cox proportional hazards models. Diabetes control and microvascular and macrovascular complications were significant risk factors for incident dementia, but adjusting for these measures imparted no substantive changes in the association between race and ethnicity and dementia incidence. In all models, dementia risk was significantly higher among Native Americans and African Americans than for all other racial and ethnic groups; also, dementia risk was significantly lower among Asians (Table 2). The largest observed difference was between Native Americans and Asians. These observations persisted even after accounting for sociodemographic characteristics, diabetes duration, markers of clinical control, and many other diabetes-related microvascular or macrovascular complications.

Greater Awareness Required

Dr. Whitmer says more work is needed to gain a better understanding of the associations between diabetes, dementia, and race and ethnicity. “More research is needed to explore the links between sociodemographic characteristics or differences in diabetes duration and how these factors affect dementia risk,” she says. Furthermore, data are needed on markers of clinical control and the effect of microvascular and macrovascular complications of diabetes on dementia incidence.

“Clinicians need to be vigilant about assessing dementia risks when managing older patients with type 2 diabetes,” Dr. Whitmer says. “Cognitive problems can be identified during patient encounters or when working with caregivers. If left unaddressed, these problems can result in negative consequences with regard to diabetes self-management. It may behoove clinicians to screen older patients with type 2 diabetes for cognitive impairment with simple tests that are quickly and easily administered. Finding out about dementia risk using electronic health records can also help. Such efforts may enable physicians to tailor treatment approaches so that they can provide optimal care to patients.” Dr. Whitmer notes that the Diabetes-Specific Risk Score for Dementia is an option to consider when calculating 10-year dementia risk for someone with diabetes.

Dr. Whitmer hopes that future analyses will explore the role of glycemic control and its potential to reduce dementia risk later in life. More data are also needed on the link between diabetes treatment and dementia risk. In the meantime, she recommends that clinicians recognize the risks of dementia among certain races and ethnicities with diabetes. “A key factor to eliminating health disparities in the care that is provided to patients is to increase awareness of the link between type 2 diabetes and dementia,” she says. “Clinicians can then take it a step further by addressing the role of race and ethnicity on these risks and talking about these correlations with patients.”

References

Mayeda ER, Karter AJ, Huang ES, Moffet HH, Haan MN, Whitmer RA. Racial/ethnic differences in dementia risk among older type 2 diabetic patients: the Diabetes and Aging Study. Diabetes Care. 2014;37:1009-1015. Available at: http://care.diabetesjournals.org/content/37/4/1009.full.

Strachan MW, Reynolds RM, Marioni RE, Price JF. Cognitive function, dementia and type 2 diabetes mellitus in the elderly. Nat Rev Endocrinol. 2011;7:108-114.

Whitmer RA. Type 2 diabetes and risk of cognitive impairment and dementia. Curr Neurol Neurosci Rep. 2007;7:373-380.

Haan MN. Therapy insight: type 2 diabetes mellitus and the risk of late-onset Alzheimer’s disease. Nat Clin Pract Neurol. 2006;2:159-166.

Whitmer RA, Karter AJ, Yaffe K, Quesenberry CP Jr, Selby JV. Hypoglycemic episodes and risk of dementia in older patients with type 2 diabetes mellitus. JAMA. 2009;301:1565-1572.