It started with a conversation about insomnia. My friend smiled, as if she were giving a wonderful gift. "Don't spend money on sleeping pills or take a narcotic. Cold pills will do the trick," she said.

I began taking the dose prescribed on the cold and flu "nighttime" package: two capsules a half hour before bedtime. Not only did I sleep soundly for eight hours or more, but I also had wonderfully vivid dreams. Problem solved!

But about three months later, something seemed wrong with my brain. During conversations, my mind would blank out on words; I'd stutter and verbally stumble. I'd forget names of friends and people I knew well. I'd forget appointments, assignments, things I was supposed to do. I'd purchase something, pay for it, then walk away, leaving my items at the counter.

It was awkward — and alarming. The increasingly serious symptoms had come on so fast — could I have had a stroke?

Finally, I began researching possible side effects from the cold pill ingredients, which is how I learned the truth. These over-the-counter pills are not harmless. They can, and do, affect the brain with long-term use, especially in people who are 50 and over. Cold pills containing diphenhydramine (an antihistamine), can cause symptoms similar to dementia. (Perhaps I would have known this if I'd talked to my doctor before taking these things long term.)

Here's the science: A healthy brain depends on neurotransmitters, which are chemicals that allow brain cells to communicate with one another. One of the most important neurotransmitters is acetylcholine, which is essential for memory and learning. Those with Alzheimer's disease have much lower levels of this chemical in their brains. Well, diphenhydramine blocks acetylcholine, according to a study published in 2009 in the Journal of Clinical Interventions in Aging.

Studies have shown that older adults who take OTC medications that block acetylcholine for more than three months at a time dramatically increase their risk of developing Alzheimer's disease.

In addition, many different medications, both OTC and prescription, contain antihistamines such as those found in Benadryl. You may be taking more than one kind of pill containing this substance, which then builds up in the brain, causing even more symptoms of cognitive impairment.

Luckily, brain functions that have been negatively affected by OTC cold medicine aren't permanent. In most people, the brain will recover totally once acetylcholine is allowed to build back up to normal levels. The restoration of this neurotransmitter in the brain will start as soon as the medication is stopped.

This doesn't mean you can't take these medications to relieve symptoms if you come down with a cold. Taking them for a few days while symptoms are at their worst won't be harmful to your brain. But taking them for a long period, or using them for sleeping pills, can be a risk.

Natural alternatives

There are several over-the-counter herbs and minerals used as sleep aids, including melatonin, magnesium and valerian. Talk to your doctor to see if one of these might be appropriate for you if you're experiencing trouble getting or staying asleep.

sunday@tribune.com