Benadryl and Other Common Medications are Linked to Dementia in Men and Women

Many people turn to over-the-counter medicines when they need relief from allergy and cold symptoms or have trouble falling asleep.  That’s why you might be concerned about a 2015 study showing that one of the most common of those drugs—Benadryl—could lead to serious health problems, including dementia.

Benadryl has many uses.  Although often taken for allergy symptoms, the same dose of the same ingredient (diphenhydramine) is used in most over-the-counter sleeping pills, and also used for motion sickness. We’ve known since 2012 that people who regularly take Benadryl or other sleeping pills to fall and stay asleep are more likely to get cancer and tend to die earlier than people who don’t take sleep medication.  A 2015 study, however, found that taking Benadryl also seems to increase a person’s chances of developing dementia.

Most people who take Benadryl don’t even know it, since the pills they buy in their local drug stores have many different names (such as Tylenol PM, Simply Sleep, Unisom, ZzzQuil, Compoz Nighttime Sleep Aid, Simply Right Sleep Aid, Allermax, and Equate Nighttime Sleep Aid).[1] Drugs containing diphenhydramine aren’t the only ones linked to an increased risk of dementia. The 2015 study, led by a researcher from University of Washington, found an increase in dementia linked to a type of drug known as anticholinergics. These drugs are known to help dry out a runny nose or tearing eyes and also to make you sleepy; they work by blocking acetylcholine, a chemical that sends messages to and from the brain and helps start muscle contractions.

In addition to Benadryl, other anticholinergics include tricyclic antidepressants such as Tofranil (Imipramine), Elavil (Amitriptyline), and Sinequan (Doxepin),[2] and medicines for overactive bladder such as Toviaz (fesoterodine); Ditropan, Gelnique, and Oxytrol (all with the generic name oxybutynin); Vesicare (solifenacin); and Detrol (tolterodine).[3] These are just a few of the many names for these drugs – if you are taking tricyclic antidepressants or medicines for overactive bladder, check them out online to see if they are similar to the drugs listed above.

The 2015 study showed that the longer and more consistently people took anticholinergics, the more likely they were to develop dementia.[4] The study included more than 3,000 men and women who were 65 or older, and they were randomly chosen from among members of the Group Health system in the Seattle area. None of the men and women had dementia at the time that they were selected for the study, and all had belonged to the health plan for at least 10 years. Using patient health records, study participants were then divided into 5 groups based on how much they used anticholinergic drugs in the 10 years before the study began (which means they were age 55 or older). These were calculated as objectively as possible, based on information including the number of times such drugs were purchased at pharmacies belonging to the Group Health system. A limitation of the study is that the purchase of over-the-counter anticholinergics at other pharmacies would not have been included.

The researchers followed the study participants for over 7 years on average to see who developed dementia. Those who had the highest exposure to these drugs (equivalent to taking an anticholinergic every day for more than three years), had a 54% higher risk for dementia compared to those who did not use anticholinergics at all. Those who had between 1 and 3 years’ worth of exposure (366-1,095 days) had a slightly higher risk for dementia than the patients with no exposure, but the difference was not statistically significant. This means it could have happened by chance. The general trend was the greater the use (as measured in days) of anticholinergics, the higher the risk of dementia. However, only the highest exposure (more than three years) had a link to dementia that researchers can say for sure was not a chance occurrence.

Taking Benadryl or other anticholinergic drugs occasionally probably won’t harm you. But, it’s important to remember that, according to this study, the more you take—and this means either the dose or the number of days—the higher your risk of developing dementia. Some of the people in the high exposure group may have been taking very low doses but they took them for a long time. Even if you think you’re not taking a lot of Benadryl or these other drugs, using them for years could put you at risk.

Bottom Line

While we can’t be absolutely sure that Benadryl (diphenhydramine) or other anticholinergic drugs cause dementia, there is now one study that suggests that it might.  When added to other studies showing a link between diphenhydramine and cancer and earlier death, it certainly raises questions about whether this very common and inexpensive medication, sold in supermarkets and drug stores across the country, is too dangerous to take on a daily basis for more than a few weeks.

All drugs tend to stay inside your body longer as we get older.  All patients, and especially those who are 55 or older, may want to avoid regular or long-term use of anticholinergics and sleeping pills. Benadryl is both an anticholinergic and a sleeping pill, so that is of even greater concern.

Many people assume that if a drug is sold without a prescription in your neighborhood store, it is safe for you to take as often as needed.  That is not true, because drugs are not tested for very long-term use before they are allowed to be sold.  Whether you have allergy symptoms, trouble falling asleep, a bladder that keeps you running to the bathroom more than you’d like, or even depression, there may be safer ways of coping with or treating the problem. And, the strategies that don’t involve medications are the ones with the least risks.

All articles are reviewed and approved by Diana Zuckerman and other senior staff.

  1. Diphenhydramine. MedlinePlus. Accessed March 26, 2015.
  2. Safer Alternatives to Potentially High Risk Medications in the Elderly. GroupHealth. Accessed March 23, 2015
  3. Anticholinergics for Urinary Incontinence in Women. WebMD. Accessed March 30, 2015.
  4. Gray SL, Anderson ML, Dublin S, et al. Cumulative use of strong anticholinergics and incident dementia: A prospective cohort study. JAMA Internal Medicine. 2015;175(3):401-407.