DEAR DR. DONOHUE: My husband, 55 years old, had his first colonoscopy a month ago. They found a polyp that wasn’t cancer. No one in his family has ever had colon cancer. Does the polyp put him at risk for it? The doctor wants him to have a repeat colonoscopy in three years. Is that too long to wait? Can my husband do anything to lessen his risk, if he has a risk? — L.O.

ANSWER: Colon cancer is the third most common cancer, but it’s the second leading cause of cancer-related deaths. Everyone at age 50 should have a colonoscopy, a scope exam of the colon. It’s the surest way to detect cancer, and it’s the best way to eliminate cancer risk by removing polyps. Polyps are benign growths from the colon lining. Polyps can become cancers if they’re neglected. It takes between five and 10 years for the cancer-prone polyp, adenoma, to become cancer. Polyps larger than two-fifths of an inch in diameter (1 cm) are likely to harbor cancer changes.

Since blacks are more apt to develop colon cancer than whites, many authorities advise that they begin colonoscopic exams at age 45.

Having had one adenoma raises the chances for developing another. Your husband’s risk is higher than it would be if he had had no polyps. The three-year interval before his next colon exam is the suggested time interval put down by many expert bodies that develop the standards for such exams. Larger polyps — larger as defined above, call for a second colonoscopy in less than three years.

Your husband, as well as all of us, can lessen his chances of colon cancer by limiting his consumption of fats, processed meats and possibly red meats. Obesity encourages the development of colon cancer, as does physical inactivity. Exercise, believe it or not, is a precautionary step. A high-fiber diet is also a preventive measure.

The booklet on colon cancer explains this illness and its treatment. Readers can order a copy by writing: Dr. Donohue — No. 505, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. DONOHUE: Please explain Parkinson’s disease. I am 86. How do you tell if you have it? — Anon.

ANSWER: Four fairly distinctive signs strongly suggest Parkinson’s disease: One is rest tremor, a shakiness of the hands when they are not engaged in any movement but quietly resting in the lap. The second is rigid muscles, muscles that are tensed so tightly that it’s hard for another to move the person’s arm. The third sign is slow movements and shrinking movements. Blinking slows. Handwriting grows smaller. All movements take an eternity to complete. A fourth major sign is walking impairment. Steps turn into a shuffle. Or they become tiny and hurried, propelling a person forward uncontrollably.

The problem in Parkinson’s is a lack of the brain chemical dopamine. Medicines can restore the dopamine supply. A neurologist is the doctor best trained to diagnose Parkinson’s disease.

DEAR DR. DONOHUE: My ophthalmologist found Hollenhorst plaque in my left eye. He was quite concerned, and dictated a letter to my primary-care doctor. He recommended an ultrasound of the carotid arteries and an echocardiogram. I did not hear from my primary-care doctor. When I talked to him, he seemed unconcerned. I would appreciate your thoughts. — L.H.

ANSWER: A Hollenhorst plaque is a cholesterol crystal that the doctor saw in one of the arteries of your left eye’s retina. For some, it causes pain and blurs vision. For others, it produces no symptoms. It most likely came from an artery at some distance from the eye artery.

You should have the tests recommended by your ophthalmologist. There might be a buildup of plaque in your carotid neck arteries. The echocardiogram will demonstrate any cholesterol buildup in your aorta.

If your primary doctor has taken a blase attitude about all this, it would be good to shake him into action. Plaque in the carotid arteries or the aorta can have dire consequences.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from