- Many popular OTC sleep aids are made from antihistamines (diphenhydramine & doxylamine succinate).
- Research shows that they do not significantly increase total sleep time. And when it comes to quality, there’s an adverse effect at the expense of REM sleep. (1)
- This is why people who take an OTC sleep aid may feel “groggy” the next morning—a side effect with potentially serious implications for older adults. (1)
- While okay for occasional use, long-term use of over-the-counter sleep aids with antihistamines was found to increase dementia risk by about 50%. (2-3)
- If you haven’t already taken stock of your medicine cabinet, be sure to do so and talk to your doctor about ways to reduce or lower the dose of your anticholinergic medications (a family of medications that contains antihistamines).
If you’ve used an over-the-counter (OTC) sleep aid, you’re not alone. According to a recent Consumer Reports study, 1 in 5 adults reported using OTC sleep aids. (1) This equates to roughly 50 million Americans—about one-third of the 164 million people who suffer from sleep issues at least once a week. (4) And while the Food and Drug Administration mandates that labels on all OTC sleep aids include language telling consumers to consult their doctor if insomnia persists for more than two weeks, a Consumer Reports national survey found that, of the 20% who took an OTC medication within the past year, almost 1 in 5 (18%) reported taking it on a daily basis, with 41% using the drugs for a year or longer. (5)
With numbers that high, one might assume that OTC sleep aids are safe and effective, right? What most people don’t realize is that there isn’t research indicating that sleep aids containing antihistamines lead to better quality sleep. (1) When taken long-term, they are even associated with a statistically significant increased risk of dementia for those 65 and older. (2)
If one (or many) of these facts is surprising, it’s due to no fault of your own. Outside of some medical communities, not many people are talking about this or aware of it. It’s time this changes. Let’s use the best of the available science and data to let folks know the truth. And if a product actually does harm, let’s help people become aware so they can use those OTC drugs safely and appropriately. They are okay for occasional use only, and with caution.
To break this down:
First things first...what are antihistamines?
Before we talk about antihistamines, it’s important to mention anticholinergics. This family of drugs works by blocking the actions of acetylcholine, a neurotransmitter that shepherds messages throughout the nervous system, impacting processes such as learning, memory, and muscle contractions.
Antihistamines are a sub-group of medications under the larger anticholinergic group. As the name suggests, antihistamines work to reduce or block histamines, which are chemicals produced by the immune system. For the most part, antihistamine medications are used to reduce or eliminate allergy symptoms. But because histamine receptors also affect wakefulness, antihistamines have a secondary use as sleep aids that induce feelings of drowsiness.
Throughout the article, you’ll see us refer specifically to diphenhydramine and doxylamine, which are two types of antihistamines.
OTC sleep aids with antihistamines do not lead to better quality sleep
Although that knocked-out feeling may lead some to believe that an OTC drug is working faster and better, science says otherwise. A Consumer Reports study found that most OTC sleep aids only increase total sleep duration by 20-30 minutes. (1) At face value, that sounds like a good thing (who wouldn’t want 30 more minutes of shut-eye?), but is it worth it when sleep quality suffers?
When you dig deeper, you’ll find that sleep time is only part of the story. The quality of your sleep—the amount of deep and REM sleep—matters, too. When you use OTC sleep aids with antihistamines, sleep quality suffers.
The reason? Acetylcholine. This neurotransmitter plays a critical role in rapid eye movement sleep, otherwise known as REM. (6) During this time of the night, brain waves are far more active, although muscles remain fully relaxed. Because of the disparity between the brain increasing activity and the muscles remaining inactive (known as atonia), REM is sometimes referred to as “paradoxical sleep.” We spend about 20-25% of our sleep time in this stage, which benefits cognitive functions such as memory consolidation, creativity, and learning. (7-8)
Because antihistamines block acetylcholine, REM sleep suffers, which is one reason why upwards of 40% of people taking OTC sleep aids report feelings of fogginess or drowsiness the following morning. (1)
“Antihistamines may help you fall asleep, but overall sleep quality is usually not very good,” explains (9) Philip Alapat, MD, assistant professor at Baylor College of Medicine. “Using an antihistamine for sleep [also] has no long-term benefit. Most people develop a tolerance quickly.”
This side effect is particularly concerning for older adults who metabolize medications at a slower rate. According to studies from Consumer Reports, 1 out of 10 adults 65 and older who take OTC sleep aids report feeling “uncoordinated, tripping, or falling.” What’s more, they’re 34% more likely to fall than those not taking sleep drugs. (1)
OTC sleep aids with antihistamines are associated with an increased risk of dementia
In two Journal of American Medicine (JAMA studies), researchers concluded that taking an anticholinergic continuously for the equivalent of three years was associated with around a 50% higher risk of dementia in older adults than taking the same dose for three months or less. (2-3) These staggering results followed a multi-year cohort study of 3,434 participants aged 65 or older with no dementia at entry. (2) Cognitive performance was measured every two years via the Cognitive Abilities Screening Instrument, which scores on a range of 0 to 100. Higher scores for better cognitive performance, lower scores for worse. If a participant scored at or below 85, s/he then underwent a formal diagnostic evaluation for dementia, which included both a comprehensive physical and neurological exam. This study was the first to evaluate dose—in other words, the higher the cumulative amount of antihistamine OTC sleep aids taken, the higher the dementia risk.
These results led scientists to believe that cumulative use of anticholinergics “results in pathologic changes in the brain similar to those observed with Alzheimer’s disease.” (2)
Remember, anticholinergics block acetylcholine—which affects, among other things, memory. If the body’s production of this substance is already decreasing with age, the last thing we want to do is take a medication that accelerates its decline.
Also worth mentioning is the fact that a reduction in REM sleep has been shown to increase the risk of dementia. Although the clinical study did not specifically consider antihistamine use, it’s notable that for every percent reduction in REM sleep, there was a 9 percent increase in the risk of dementia. (10)
“It is clear that REM sleep is an important contributor to the risk of developing dementia and steps should be taken to address this—through a modification of OTC regimen or behavioral sleep interventions—so dementia can be delayed or even prevented,” explains Adam Perlman, MD, MPH, Director for Integrative Health & Wellbeing for Mayo Clinic Florida.
Alternative ingredients for safe + effective sleep support
Hundreds of positive human clinical studies show that various natural, safe supplement ingredients support sleep in two major ways:
- Directly impacting sleep quality or quantity (physical)
- Indirectly supporting sleep by reducing everyday stress and promoting a sense of calm and relaxation (emotional + behavioral)
Eight of the most effective, non-antihistamine ingredients that directly or indirectly promote healthy sleep are:
- Valerian Root
- Lemon Balm
Learn more about the science behind WHY these ingredients work in our complete guide.