After chemotherapy, breast cancer patients tend to find themselves more forgetful than before.

This phenomenon, known among scientists as "chemobrain", could have a genetic link, two local experts have found.

Those with a variant of a certain gene are protected against the effects of chemotherapy, and are less likely to suffer forgetfulness or worsening language skills.

"You would assume that if they were normal to start with, they would be normal after chemotherapy ends," said Associate Professor Alexandre Chan of the National University of Singapore.

"But a lot of our patients are unable to function as well as they used to."

He and his team from the science faculty's pharmacy department studied 145 early-stage breast cancer patients between December 2011 and April last year.

They measured the women's cognitive functions - such as their memory and ability to multitask - before, during and after chemotherapy.

The gene in question is usually associated with memory and brain development. Of the 145 patients, 54 reported cognitive impairment after chemo.

Those with the genetic variant were found to suffer less impairment where verbal fluency and multitasking ability were concerned.

These findings are important, said Prof Chan, because breast cancer is not only the most common cancer among women in Singapore, but also one of the most treatable.

"A lot of these people will want to go back to work, and if their cognition is affected, we are very concerned," he said.

The team is now collecting more patient samples to validate its findings. It hopes to eventually help better prepare breast cancer patients for the effects of chemobrain.

"If there's a very strong association, we could screen them beforehand and... perhaps help them reduce the impact," said doctorate student Terence Ng, who was also involved in the study.

"It's a small piece in a bigger puzzle."