SATURDAY, May 3 (HealthDay News) -- Two new studies show that anticholinergics, a commonly prescribed group of drugs, may cause elderly people to "slow down" in their daily physical activities.

The two reports from researchers at Wake Forest University School of Medicine support findings released a few weeks ago that anticholinergic drugs -- which treat a variety of diseases and conditions, including acid reflux, Parkinson's disease and urinary incontinence -- may cause older people to lose their thinking skills more quickly than those who don't take the medicines.

Anticholinergic drugs work by stopping acetylcholine, a chemical that enhances communication between nerve cells in the brain, from binding to its receptors in nerve cells.

In the first Wake Forest study, older adults taking anticholinergics became more likely to walk more slowly and to need help in other daily activities.

"These results were true even in older adults who have normal memory and thinking abilities," study author Dr. Kaycee M. Sink said in a prepared statement. "For older adults taking a moderately anticholinergic medication, or two or more mildly anticholinergic medications, their function was similar to that of someone three to four years older."

Common anticholinergic medicines cited in the study included the blood pressure medication nifedipine (Adalat or Procardia), the stomach antacid ranitidine (Zantac) and the incontinence medication tolterodine (Detrol).

The findings, which involved more than 3,000 people, average age 78, were scheduled to be presented Saturday at the American Geriatrics Society annual meeting, in Washington, D.C.

In a separate Wake Forest study, published online in April in the Journal of the American Geriatrics Society, Sink found that older nursing home residents who took medicines for dementia along with anticholingerics for incontinence declined in function 50 percent faster than those only treated only for dementia.

"Over a year's time, the decline we observed would represent a resident going from requiring only limited assistance in an activity to being completely dependent, or from requiring only supervision to requiring extensive assistance in an activity," said Sink, an assistant professor of internal medicine-gerontology at Wake Forest.

The seniors in the second study had completed at least two consecutive prescriptions for cholinesterase inhibitors, a family of drugs used to treat dementia by increasing levels of acetylcholine. These include donepezil (brand name Aricept), galantamine (Razadyne), rivastigmine (Exelon) and tacrine (Cognex).

About 10 percent of those studied were also taking either oxybutynin or tolterodine, the two most commonly prescribed drugs for urinary incontinence.

"The two drugs are pharmacological opposites, which led us to hypothesize that the simultaneous treatment of dementia and incontinence could lead to reduced effectiveness of one or both drugs, Sink said.

As an estimated 33 percent of people with dementia also take a medicine to control incontinence, this finding is especially alarming.

The two studies suggest that physicians should carefully consider the implications when prescribing anticholingeric medications to older adults.

More information

The U.S. National Institute on Aging has more about older adults and medications.