People who've had cancer are 40 percent more likely to report having memory problems than people who haven't, a new study suggests.

The finding reveals that memory problems in cancer patients are more prevalent than previously assumed, though they still aren't sure of the exact reasons why, said Pascal Jean-Pierre, assistant professor at the University of Miami Miller School of Medicine.

"It's a big problem," Jean-Pierre told MyHealthNewsDaily. "With cancer-related cognitive dysfunction, the challenge is, for some patients, very subtle and mild problems, and for others, it's a more significant problem that can impact quality of life."

The reasons for the memory problems are still largely unknown, but scientists say a combination of factors could be at work, including the tumor's biology, effects of chemotherapy and radiation treatments and stress from having cancer, he said.

Researchers looked at data from the National Health and Nutrition Examination Survey, which includes responses from nearly 10,000 people ages 40 and older, about 1,300 of whom had cancer at the time of the survey, or had it previously. The survey included the question: "Are you limited in any way because of difficulty remembering or because you experience periods of confusion?"

Researchers found that 14 percent of cancer survivors and patients had memory impairment that impacted their daily lives, compared with 8 percent of people who did not have cancer, the researchers said. The results held true when they took into account factors such as age, poverty and general health.

Memory problems associated with cancer treatments aren't new. "Chemo brain" a mental cloudiness after undergoing chemotherapy treatment is commonly experienced by cancer patients, according to a 2010 article in the journal Advances in Experimental Medicine and Biology.

The prevalence of "chemo brain" can range anywhere from 15 to 70 percent, according to the American Cancer Society.

The new study's finding that 14 percent of patients reported memory problems was at the low end of estimates because it included people who went through non-chemo treatments, and didn't take into account the time between treatment and when patients took the questionnaire, Jean-Pierre said.

Because chemo brain is a short-term problem for most cancer patients, according to the Mayo Clinic, and the new study included responses from people who could have had cancer decades ago, memory problems could have been underreported by people whose memory problems have since subsided, he said.

But still, the findings underscore the need to deliver treatment to patients dealing with memory problems, Jean-Pierre said.

"The first step would be for the patient to report it and symptoms if they have them," he said. "And if there is a problem, the physician can refer for testing that will help determine what's going on there, and then they can look at behavioral intervention or drug intervention."

Now, Jean-Pierre said, the next step is to discover the biological processes that link cancer with memory problems. He also hopes to find ways to improve the quality of life for cancer patients and survivors.

The study was presented Oct. 1 at the Third American Association for Cancer Research Conference on The Science of Cancer Health Disparities.