April 26 (UPI) -- A new study has linked common antidepressants and incontinence medications to increased risk of dementia -- even if the drugs are taken 20 years before diagnosis.
Researchers from the United States, Britain and Ireland found anticholinergic drugs, which are often prescribed as antidepressants and for incontinence, may increase risk for dementia, based on analysis of 27 million prescriptions given to 40,770 people over age 65 who were diagnosed with dementia between April 2006 and July 2015.
After comparing the dementia patients' records with 283,933 older adults who did not have dementia, the researchers found a 30 percent increased risk of developing the condition after taking the drugs. The study's findings were published this week in BMJ.
About 7.6 percent of people aged 12 years and over has been diagnosed with depression, according to the Centers for Disease Control and Prevention. And about 50 percent of women and 25 percent of men said they had bladder incontinence, according to the CDC.
"Middle aged and older populations are increasingly taking multiple drugs, but the potential adverse events of long term use are not well understood," the researchers wrote.
Anticholinergics, which block acetylcholine, a nervous system neurotransmitter, have previously been associated with potential cause of cognitive impairment. The drugs have been prescribed for depression, gastrointestinal disorders, Parkinson's disease, urinary incontinence, epilepsy and to manage allergies.
Commonly used anticholinergic prescription drugs include Levsin, Donnatal, Pamine, Librax, Symax Duotab, Bentyl and Transderm-Scop.
"This study is large enough to evaluate the long-term effect and determine that harm may be experienced years before a diagnosis of dementia is made," study co-author Dr. Noll Campbell, a researcher at the Regenstrief Institute in Indianapolis and Indiana University Center for Aging Research, said in a Regenstrief press release.
For the study, the researchers utilized data derived from Clinical Practice Research Datalink in Britain, and the participants selected had a median age of 83.
Among the patients whose medical data was analyzed for the study, 35 percent with dementia and 30 percent without were prescribed at least one anticholinergic drug.
Dementia was linked to increasing exposure to antidepressant, urological and antiparkinson drugs. And they said it was noticed 15 to 20 years before diagnosis.
The proportion of dementia cases diagnosed with depression at the start of drug treatment was 12 percent, but rose to 20 percent during use.
While study author Dr. Ian Maidment, a senior lecturer in clinical pharmacy at Aston University, urged medical providers to de-prescribe anticholinergic drugs, another of the study's authors recommended caution because more research is necessary to understand the link between the drugs and dementia.
"We don't know exactly how anticholinergics might cause dementia," said study co-author Dr. Chris Fox, a professor of clinical psychiatry at UEA's Norwich Medical School. "Further research is needed to understand possible reasons for this link. In the meantime, I strongly advise patients with any concerns to continue taking their medicines until they have consulted their doctor or pharmacist."