I swear I don’t go looking for alarming news about benzodiazepines, drugs widely prescribed for insomnia and anxiety. But it shows up with some frequency, so, mindful of your fervidly held views on the subject, I am donning a hazmat suit to bring you the latest findings from the medical journal BMJ.

They’re disturbing.

In previous posts, I reported that long-term use by older people of drugs called sedative-hypnotics, which includes benzos (like Ativan, Xanax, Valium and Klonopin) and the related “z-drugs” (Ambien, Lunesta), has for years caused concern among some researchers.

Some readers took exception, arguing that critics minimize the miseries of chronic sleeplessness, reflexively condemn all drug dependence or condescendingly assume older people can’t make smart decisions. “The Ambien I use is low dose and I am not an idiot,” commented a miffed Margaret Moffitt of Roanoke, Va.

The doctors and health organizations I have spoken to, however, point to much higher rates of falls and fractures, auto accidents and cognitive problems in older patients taking sedative-hypnotics, along with increased emergency room visits and hospital admissions. Hence, the American Geriatrics Society’s inclusion of these drugs in its Choosing Wisely list of treatments that doctors and patients should question.

Now French and Canadian researchers are reporting — in a study designed with particular care — that benzodiazepine use is linked to higher rates of subsequent Alzheimer’s disease, and that the association strengthens with greater exposure to the drugs.

“The more the cumulative days of use, the higher the risk of later being diagnosed with dementia,” Dr. Antoine Pariente, a pharmacoepidemiologist at the University of Bordeaux and a co-author of the study, told me in an interview.

He and his colleagues reviewed medical records of almost 1,800 older people diagnosed with Alzheimer’s in the public health insurance program in Quebec, and compared them with nearly 7,200 control subjects. Most were over age 80.

About half those with Alzheimer’s and 40 percent of the control subjects had used benzodiazepines, the researchers found. That translated to a 51 percent increase in the odds of a subsequent Alzheimer’s diagnosis among the benzodiazepine users.

It was not short-term use that drove that finding: Older people who took prescribed doses for 90 days or fewer over the course of the study — patients were followed for six years or longer — had no increased risk.

But those who took the drugs longer were more likely to be diagnosed with Alzheimer’s. In older patients who took daily doses for 91 to 180 days, the risk rose 32 percent, compared to those who took none. In those who took daily doses for more than 180 days, the risk was 84 percent higher.

The association persisted whether users took 180 doses over six months or over five years, Dr. Pariente said. It also held when the researchers controlled for health and demographic factors, including conditions like anxiety, depression and insomnia.

The link was stronger to longer-acting forms of the drug, like Valium, than to formulations that leave the body more quickly, like Ativan and Xanax.

Annoyed comments may already be on their way, so let me address a few likely objections:

Objection! This is just another example of “correlation, not causation.”

Does the study show that extended benzodiazepine use causes Alzheimer’s? No, an observational study like this can never directly answer that question. But “the stronger association observed for long term exposures reinforces the suspicion of a possible direct association,” the researchers wrote.

Dr. Malaz Boustani, a geriatrician at Indiana University Health and a co-author of an accompanying BMJ editorial, praised the study’s design, which attempts to correct for what is sometimes called “reverse causation bias”: the danger, as Dr. Pariente put it, that “it’s not the drug that caused the disease. It’s the early symptoms of the disease that caused the drug use.”

Because Alzheimer’s symptoms develop slowly and can include some of the very problems (like anxiety and insomnia) for which doctors prescribe benzos, the study looked at Alzheimer’s patients who had not taken benzodiazepines for five years before their diagnoses. Their use of the drugs occurred five to 10 years earlier than that.

“They really did everything possible to overcome methodological issues,” Dr. Boustani said of the researchers.

Objection! Taking benzos only occasionally — once or twice a week, perhaps — has no impact.

Not in this study. Whether these elderly Quebecois took 180 daily doses in a row or spread them out over years, their risk of later developing Alzheimer’s disease was nearly double that of people who did not take the drugs or who stopped at 90 doses.

And many people don’t stop at 90, or stop at all. “The problem is chronic use, especially in the very elderly,” Dr. Pariente said. “You develop a tolerance and a dependency.”

Objection! What about relative versus absolute risk?

For some ailments, an increase in risk of 51 percent or even 84 percent still means people face very low risk. But dementia affects roughly 25 to 30 percent of the population over 80; Alzheimer’s accounts for about 70 percent of that. The projected numbers are sobering. To date, the search for drugs, treatments, even basic causes has been discouraging.

What if, instead of regarding these findings as scolding about drugs, we saw them as a possible finding about Alzheimer’s prevention? “Stopping these medications is such an easy, cost-effective potential therapy,” Dr. Boustani said.

Maybe that is a bit optimistic. But remember that in a different Quebec study, a brochure alone helped 27 percent of long-term, elderly benzo users to taper down (no one should simply stop these drugs cold) and discontinue their prescriptions within six months. Another 11 percent reduced their dosage.

People don’t want to part with their sleeping pills, I told Dr. Boustani, remembering our earlier discussions. They don’t see why they should.

His reply: “Tell them: ‘Here is the information. Take this into account when you decide to take a sleeping pill or not.’ ”

“If you’re willing to take the risk, O.K.,” he added. “You’re making an informed decision.”