Question: Are there any tests out there for Alzheimer's disease?

Answer: As of now, the only definitive test for Alzheimer's disease is the analysis of brain tissue after death. That's why folks with a presumptive diagnosis of Alzheimer's disease are described as having "senile dementia of the Alzheimer's type." However, there may soon be a new blood test that can accurately diagnose Alzheimer's and differentiate it from other forms of dementia.

Researchers at Canada's McGill University have found there is a dramatic difference between the production of the hormone DHEA in folks with Alzheimer's disease versus those without dementia or even other forms of dementia. DHEA is a natural steroid hormone produced by the adrenal glands, the testicles, and the brain. It affects a wide array of bodily characteristics, including mood, memory, physical stamina, and immune and stress response.

Researchers found that blood from a person affected with Alzheimer's does not show a rise in DHEA production when subjected to oxidation, whereas blood from a non-Alzheimer's person shows a dramatic rise in the level of DHEA when subjected to the same blood oxidation. The lack of ability to produce DHEA through oxidation in the blood allows for a simple lab test to identify someone affected with Alzheimer's. DHEA supplementation may help memory, but has been shown to be ineffective in the treatment of Alzheimer's. The test will require FDA approval in the United States before it can be commercially available.

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What could be causing this yearlong cough?

Q: I've had a chronic cough for over a year now. My doctor has tried giving me cough medication, heartburn medication, and an inhaler, all without much success. I had a chest X-ray and that was fine. What do you think might be causing my annoying cough?

A: Coughing is the second most common reason folks seek medical attention, after pain. I don't have any information about your medical history or if you're a smoker, so I'll list some possible causes.

Smokers (or folks with prolonged exposure to secondhand smoke) often develop a chronic cough due to a low-grade chronic bronchitis. If your cough is worse in the evening, at night, or in the early morning, a postnasal drip may be causing a tickle. Intranasal steroid sprays like Flonase can take down nasal swelling that's contributing to a drip. Atrovent is another type of nasal spray that works great to dry up a drip. If an allergy is causing it, an antihistamine will help. Acid reflux in the absence of heartburn is a sneaky cause of coughing that you won't want to miss. Medications like Prilosec are great for that.

Asthma is another tricky one because it sometimes causes a cough without any wheeze. There are two ways to approach this suspect: (1) a methacholine test to try to provoke asthma, and (2) empiric use of an albuterol bronchodilator along with a steroid inhaler. Chronic sinus infection can cause a persistent cough, and sinus films may help to identify this as the cause. ACE inhibitor blood pressure medications are well-known potential causes of cough. Look for mold or excessive dust in the home or workplace as potential causes. A new pet is also a consideration.

Mitchell Hecht specializes in internal medicine. Send questions to him at: "Ask Dr. H.," Box 767787, Atlanta, Ga. 30076. Due to the large volume of mail received, personal replies are not possible.