Diabetes and Alzheimer's: Insulin resistance increases risk

diet, exercise, diabetesDiabetes increases your risk of Alzheimer's. Reduce this risk by controlling your blood sugar. Diet and exercise can help.

Public health officials were already concerned about the projected increase in the number of Alzheimer's cases that will occur simply because the aging baby boom generation is so large. Now they worry there may be even more Alzheimer's cases than expected.

That's because diabetes — a strong risk factor for dementias like Alzheimer's — also becomes more common with age. Type 2 diabetes, which is by far the most common form of the disease, often occurs in people who weigh too much and exercise too little — a group that includes a large proportion of baby boomers.

Luckily, type 2 diabetes can often be prevented if you maintain a healthy weight and exercise regularly. And if you already have diabetes, controlling your blood sugar with diet and medication, if needed, appears to decrease your risk of Alzheimer's.

How diabetes accelerates dementia

Your body changes the food you eat into glucose, the sugar that fuels all your cells. People who have type 1 diabetes don't produce enough insulin, a hormone that makes it possible for glucose to enter your cells. People with type 2 diabetes produce enough insulin, but their cells resist the hormone's action and fail to take up enough glucose.

Scientists have identified several ways in which the abnormal insulin and blood sugar levels in diabetes could promote the brain damage that causes dementia. These proposed mechanisms are closely related, so they all may operate in concert. Here are the leading possibilities.

High blood sugar and blood vessel damage

When your blood sugar is too high, it damages your blood vessels. This damage may first become evident in the tiny vessels of your eyes and feet, but it can also affect your brain. Small-vessel damage in the brain often contributes to vascular dementia.

While vascular dementia and Alzheimer's disease are separate types of dementia, they often occur together. Some scientists have suggested that vascular dementia may deplete a person's cognitive reserve, making Alzheimer's symptoms appear earlier.

Insulin in the brain

Before full-blown type 2 diabetes develops, your body becomes less responsive to insulin. The result is elevated blood sugar, a condition sometimes referred to as prediabetes. Your body compensates by producing more insulin.

A modest increase in insulin makes more glucose available to brain cells, resulting in improved memory. But if you're insulin resistant and the level of insulin in your bloodstream remains high, the brain takes measures to slow the transport of insulin across the blood-brain barrier. That reduces the amount of insulin in the brain, making less glucose available to nourish brain cells.

Researchers have found that some people with Alzheimer's experience improved memory when they use a nasal spray containing insulin. The nasal spray bypasses the bloodstream to deliver the insulin directly to the brain.

Insulin, amyloid and inflammation

Excessive insulin in the bloodstream may trigger increased production of beta-amyloid, a segment of a protein the body normally makes. In Alzheimer's disease, beta-amyloid builds up in the brain, forming clumps, or amyloid plaques. Excess insulin may also be responsible for brain cells' failure to clear beta-amyloid.

This whole process appears to be worsened by inflammation, another side effect of high levels of insulin in the blood.

Reduce your risk

You can counter insulin resistance through modest weight loss and exercise. If you have prediabetes, you can cut your risk of developing type 2 diabetes in half by losing 5 percent of your body weight — 10 pounds for a 200-pound person — and exercising 30 minutes most days of the week.

In addition to reducing your risk of diabetes and Alzheimer's, these lifestyle changes can also help protect you from heart attacks and strokes.

source - Mayo Clinic