Bladders do not appear to shrink with age, suggesting that urinary troubles in older people can no longer be considered a normal part of aging, according to new study findings released this week.

Investigators from the University of Pittsburgh in Pennsylvania found that women between the ages of 22 and 90 had bladders that could hold roughly the same amount of fluid.

However, as women age, they become more prone to a condition called overactive bladder, in which their bladders went into spasm before becoming full, giving them an overwhelming, urgent need to urinate.

These findings suggest that when women have to urinate more often and more urgently as they age, that is "not a normal part of aging," study author Dr. Neil Resnick told Reuters Health. Instead, these women likely have overactive bladder, which can be treated, he said.

During the study, Resnick and his colleagues used a catheter to fill the bladders of 95 women. They measured how much liquid bladders could hold, how soon women could sense their bladders were filling up, and the strength of sphincter muscles that keep liquid from escaping the bladder before women can get to the bathroom.

The researchers found that as women aged, their sphincter muscles tended to weaken. Furthermore, older women were less able to sense their bladder was filling, which meant they had less warning before they would urgently need to urinate.

However, the total volume of the bladder did not appear to change as women aged.

In an interview, Resnick explained that earlier studies have suggested that women's bladders do, in fact, shrink with age. However, these investigators may have been "misled" by overactive bladder problems, since many older women likely experienced muscle spasms that caused them to urinate before their bladders were completely full. This makes bladders appear much smaller than they really are, Resnick noted.

In the current study, "people at age 90 had the same capacity as people in their 20s or 30s," he said.

People dealing with overactive bladder have a few options to treat the condition, Resnick noted, such as cutting back on fluids, urinating more frequently, exercises to retrain the bladder, or medication.

The current study was not funded by any company that makes or sells a treatment for overactive bladder, Resnick said.

He and his colleagues presented the findings on Tuesday at the annual meeting of the American Urological Association in San Antonio, Texas.