Diabetes associated with cognitive decline, CABG better than PCI for diabetics

Higher HbA1c at midlife was associated with greater cognitive decline over the following 20 years, and coronary artery bypass grafting is preferable to percutaneous coronary intervention in diabetics, according to studies recently published in Annals of Internal Medicine.


Higher HbA1c at midlife was associated with greater cognitive decline over the following 20 years, and coronary artery bypass grafting is preferable to percutaneous coronary intervention in diabetics, according to studies recently published in Annals of Internal Medicine.

In the first study, researchers used cohort data from the community-based Atherosclerosis Risk in Communities study, which measured the HbA1c of 13,351 black and white adults who were aged 48 to 67 years in 1990 to 1992. At baseline and 20 years later, the participants' cognitive performance was measured by delayed word recall, digit symbol substitution, and word fluency and was summarized in a global Z score. Results were published in the Dec. 2 Annals of Internal Medicine.

Patients with diabetes (defined by self-report, medication use, or HbA1c ≥6.5%) had 19% greater cognitive decline over 20 years than those without diabetes (adjusted global Z-score difference, −0.15). Even patients with prediabetes (HbA1c 5.7% to 6.4%) had a significant increase in cognitive decline compared to those with lower HbA1c. Poorly controlled diabetes (HbA1c ≥7%) was associated with greater cognitive decline than controlled diabetes (adjusted global Z-score difference, −0.16), as was longer duration of diabetes. No association with race was observed.

The association of diabetes with cognitive decline was mostly driven by decreases in scores on digit symbol substitution and word fluency, suggesting that the cause may involve the subcortical microvasculature, the study authors suggested. They noted that excluding patients with stroke attenuated the results but that the adjustment for attrition worked in the opposite direction, and so the study's estimate of the association between higher HbA1c and cognitive decline may actually be conservative.

Because glucose levels are potentially modifiable, diabetes control “may offer an important opportunity for the prevention of cognitive decline, thus delaying progression to dementia,” the study authors concluded. Interventions should be attempted and studied for their potential individual and public health benefits, they said.

In the second study, authors reviewed the literature and identified 40 randomized, controlled trials comparing coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI) in diabetic patients with multivessel or left main coronary artery disease. Subsequent meta-analysis revealed that the primary outcome—a composite of all-cause mortality, nonfatal myocardial infarction, and stroke—was increased with PCI. PCI resulted in increased mortality, no change in the number of myocardial infarctions, and fewer strokes. The authors concluded that “coronary artery bypass grafting seems to be the preferred revascularization technique in diabetics, especially if long term-survival is anticipated.”

The Nov. 18 issue of Annals also included a study comparing print and electronic diabetes education tools used by community health workers. Annals of Internal Medicine's Diabetes Collection, which includes recent journal articles, In the Clinic features, and summaries for patients, is available online.