Johns Hopkins Health Alert
Research Findings on Diabetes, Alzheimer's Risk, and Vision Problems
Diabetes Update 1 -- High Levels of Insulin May Increase Alzheimer's RiskElevated levels of insulin can cause inflammation in the brain that may increase the risk of Alzheimer’s disease (AD). This finding was reported in the Archive Of Neurology (Volume 62, page 1539).
Researchers studied 16 healthy adults aged 55–81 years who were given a high dose of insulin by infusion one day and a saline placebo infusion another day. Both days, participants gave blood samples for plasma glucose levels. They also underwent lumbar puncture for cerebrospinal fluid samples for analysis. The moderately high levels of insulin produced by the infusion were like those seen in people with insulin resistance who eat a high-fat, high-carbohydrate diet. These higher insulin levels caused an immediate increase in cerebrospinal fluid markers of inflammation in the brain and spinal cord. They also had higher levels of beta-amyloid, a protein that accumulates in the brains of people with AD. These changes were not seen after placebo infusions.
The findings suggest that moderately high insulin levels in people with diabetes or insulin-resistance may increase the risk of AD by causing inflammation in the brain. The authors emphasize the importance of good blood glucose control in both those with diabetes as well as people who don’t have diabetes but have impaired glucose tolerance.
Diabetes Update 2 -- High Blood Glucose Levels Cause Temporary Vision Problems
People with diabetes often complain that their eyeglass prescription must be wrong. These vision problems are often caused by high levels of plasma glucose and may correct themselves when glucose control improves.
Researchers performed a complete eye examination in 18 people with diabetes who had high blood glucose levels (over 300 mg/dL). All of the patients wore ordinary eye glasses. The ophthalmologic examination was repeated after diabetes patients underwent treatment to reduce their plasma glucose levels to 200 mg/dL or less. The treatment-related decrease in blood glucose often caused small but significant changes in measures of the refractive error in their eyes. Nine diabetes patients became more farsighted, two became more nearsighted, and seven showed no vision change. Significant changes also occurred in the curvature of the cornea of their eyes. Although these changes were small, they could cause people to be dissatisfied with eyeglasses that had been recently prescribed.
The researchers conclude that people with diabetes should wait until their blood sugar is under good control before getting a new eyeglass prescription or having cataract surgery or corneal refractive procedures. Reported in the journal Cornea (Volume 24, page 531).
Posted in Diabetes on June 14, 2007
Reviewed September 2011
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