"The association between diabetes mellitus and increased risk for dementia in the elderly is well documented," the authors write as background information in the article. Several possible mechanisms have been proposed for this association, including the direct effects of high blood glucose and insulin, the build-up of beta-amyloid plaques in the brain and the effects of diabetes-related vascular disease on blood vessels in the brain.
Joshua A. Sonnen, M.D., of the University of Washington, Seattle, and colleagues studied 196 individuals who were part of the Adult Changes in Thought Study, a community-based investigation of dementia. After the participants died, their brains were autopsied and their cases were divided into four groups based on clinical information: those with diabetes and dementia, those with diabetes but not dementia, those with dementia but not diabetes and those without either disease.
In the 125 patients without dementia, neuropathological and biochemical factors did not differ based on diabetes status. However, among the 71 with dementia, two patterns of injury emerged based on whether the patients had diabetes and received diabetes treatment. Those without diabetes had larger amounts of beta-amyloid buildup and greater free radical damage, whereas those with diabetes had more microvascular infarcts (microscopic injury to small blood vessels in the brain known as arterioles) and more inflammation in neural tissue. This pattern was related to diabetes treatment, in that patients with dementia receiving treatment for diabetes had more microvascular infarcts, and untreated diabetic patients with dementia had beta-amyloid build-up similar to non-diabetic patients with dementia.
"These novel characterizations of two apparently different patterns of injury in dementia depending on diabetes mellitus status may have important etiologic and therapeutic implications," the authors conclude.
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Among individuals without any prior cardiovascular disease or diabetes, 72.1 percent had admission LDL levels less than 130 mg/dL, which is the current LDL cholesterol target for this population. Thus, the vast majority of individuals having their first heart attack would not have been targeted for effective preventative treatments based on the criteria used in the current guidelines.
The team also found that half of the patients with a history of heart disease had LDL cholesterol levels lower than 100 mg/dL, and 17.6 percent of patients had LDL levels below 70 mg/dL, which are guideline targets for LDL cholesterol in those at fair risk and at high risk for cardiovascular disease, respectively.
The study also showed that HDL cholesterol, or "good cholesterol," levels have dropped in patients hospitalized for heart attack over the past few years, possibly due to increasing rates of obesity, insulin resistance and diabetes.
Researchers found that 54.6 percent of patients had HDL levels below 40 mg/dL. Developing more effective treatments to boost HDL levels may help reduce the number of patients hospitalized for heart attacks, according to the authors.
"We found that less than 2 percent of heart attack patients had both ideal LDL and HDL cholesterol levels, so there is room for improvement," said Fonarow.
Fonarow said that only 59 percent of patients in the database had their lipid levels checked upon admission, which should be increased, since these early measurements can often help guide treatment decisions.
He also noted that only 21 percent of patients in the study were taking lipid-lowering medications before admission, despite almost half having a prior history of cardiovascular events, which would prompt treatment.
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