Dozens of Calgary seniors are alarmed after learning their credit-card numbers, addresses and health-card numbers were stored on computers that were stolen recently.

The Academy Hearing Centre in Brentwood Mall, which provides hearing tests and equipment, mostly to seniors, recently mailed out letters warning of the theft.

"I got scared," said one elderly female client who purchased a hearing aid from the company.

She requested that her name not be released because she is worried about her security.

The woman said the thieves nabbed her name, address, health information and Alberta health-care number.

"It's the same thing, like somebody steals your social insurance number," she said.

She added that she was unable to change her health-card number.

"I called up Edmonton, the health insurance centre, and she said you have to wait about six months. Just have to notify your doctor, the family doctor. So somebody might be using my number, so let's hope it won't happen."

The Academy Hearing Centre refused the CBC's request for an interview, saying only that there is no need for clients to be alarmed.

But Tom Keenan, a University of Calgary computer science professor, said even small amounts of personal information can pose a risk.

"People need to be very, very careful," he said. "Any piece of information is part of a building, sort of edifice of credibility, and you should never let any of it out unnecessarily."

Acting Sgt. Kathy MacDonald, with the Calgary Police Service, said anyone who has had their information stolen should be on the lookout for any suspicious contacts.

"Be suspicious about hang-up calls. People that are maybe trying to get a hold of you. And maybe incoming mail that looks suspicious or maybe your mail has been rerouted," she said.