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What did the new study involve?

The research, conducted by Carol Coupland, a professor of medical statistics in primary care at the University of Nottingham in England, and colleagues, evaluated anticholinergic drugs prescribed to nearly 285,000 people age 55 and older. About 59,000 of them had a diagnosis of dementia. The information came from a database of medical records from patients in more than 1,500 general practices in Britain, the authors said.

Researchers looked at the medical records of patients who were diagnosed with dementia and examined the drugs they had been prescribed from 11 years to one year before their diagnosis. They compared their medications during that time frame with those of people who did not have a diagnosis of dementia. They recorded which of 56 anticholinergic medications people were prescribed, and at what dose and how long. They accounted for factors like body mass index, smoking, alcohol consumption, other medical conditions and use of other medications.

The study found a 50 percent increased risk of dementia among people who used a strong anticholinergic drug daily for about three years within that 10-year period. The association was stronger for antidepressants, bladder drugs, antipsychotics and epilepsy medications, the study said. Researchers did not find any increased risk of dementia with antihistamines, bronchodilators, muscle relaxants or medications for stomach spasms or heart arrhythmias.

The link between anticholinergic drugs was stronger for people diagnosed with dementia before they turned 80 and in people with vascular dementia compared to people with Alzheimer’s disease, the authors reported.

What are the limitations of the research?

An important caveat with this type of study is that it is observational — meaning there is no way to know if the medication use played any direct role in causing dementia. All it shows is that the risk of developing dementia appears to be higher for people who take some of these medications.

It’s also possible, the authors note, some conditions, like depression, may be early harbingers of cognitive decline. It’s possible, for example, that some people taking antidepressants might actually be being treated for what will turn out to be an early symptom of dementia, so it’s their depression that goes along with an increased risk of dementia — not the medicine they are taking to treat it.

What’s the bottom line?

It’s possible, but not proven, that some anticholinergic drugs increase the risk of dementia. If you need long-term treatment for one of the relevant medical conditions, talk to your doctor about other medication options that are not in the anticholinergic class, such as antidepressants like Celexa and Prozac. In many cases, there may be choices.