DEAR DR. ROACH: I’m the only person in the history of mankind whose blood pressure goes up when I sleep. There seems to be no cause. In addition, I’m resistant to medication; I’ve tried 21 different kinds. All give me terrible side effects and don’t bring my blood pressure down. The only one that works is clonidine. The side effects are terrible — sleepiness and no motivation — but at least I can deal with that.

Recently clonidine stopped working, and I went from 0.1 mg per day up to 0.4 mg per day in a matter of six weeks after being on it for two to three years. A month ago, I was put on a 0.4 mg weekly patch. This has been much better, as it’s removed about 50% of the sleepiness.

I’m 69 and a nationally ranked senior singles tennis player. I have a good diet and am in good shape. My blood pressure usually spikes between 1:30 to 3:30 at night. It even goes up when I take a 40-minute nap. I’ve been tested for everything: heart, renal artery, carotid artery, kidney, tumors, etc. I sure would like to know the cause of these spikes when my body is completely relaxed and experiencing no emotional triggers. Have you or any of your associates ever heard of such a thing? — M.H.

ANSWER: The blood pressure normally goes down 10% to 15% on average when a person is asleep, a phenomenon called “dipping.” This is found by measuring someone’s blood pressure very frequently over 24 hours with a blood pressure monitor. There are people who do not dip, called appropriately enough, “nondippers.” Some people (you are NOT the only one) experience a blood pressure increase at night, called nocturnal hypertension. There have been studies showing worse outcomes, including a higher risk for heart disease and stroke, in both nondippers and those with nocturnal hypertension.

It is not always clear what is causing people to have this condition. Kidney disease and previous heart problems are associated with dipping. That’s why you were tested for those, along with some others. The recent dramatic increase in blood pressure medication need is concerning, and a comprehensive look for any unusual causes was certainly indicated.

Treatment for nondippers often includes giving blood pressure medication at nighttime. This is not available for you, since a clonidine patch gives medication at a continuous level night and day throughout the week. Melatonin has also been tried to alleviate nondipping, although there has not been any clear benefit to this approach yet proven.

Clonidine works at the level of the brainstem, so it is ideal for blood pressure that is mediated by brain issues. One potential cause for which you have not mentioned being checked is obstructive sleep apnea, where people stop breathing at night for a few seconds (or even longer). Sleep apnea often causes difficult-to-manage high blood pressure, and may cause nocturnal hypertension or nondipping. The most effective drug is often clonidine. Physicians sometimes forget that even healthy athletes can have OSA. If you have not had an evaluation for OSA, your physicians should consider it. Sleepiness during the day is a cardinal symptom of obstructive sleep apnea.

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Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or send mail to 628 Virginia Dr., Orlando, FL 32803.