Seniors are five times more likely to be hospitalized for adverse drug reactions compared to all other Canadians, according to the Canadian Institute for Health Information.

A report released on Tuesday by CIHI found that from 2010 to 2011, one in 200 Canadians age 65 or older was hospitalized because of an adverse drug reaction, compared with one in 1,000 Canadians under the age of 65.

This means that around 27,000 Canadian seniors were hospitalized as a result of a drug reaction, CIHI said.

The report also found that ADR-related hospitalizations are on the rise.

“We did find that the number of hospitalizations related to adverse drug reactions was increasing at about three per cent per year,” Michael Gaucher, the report’s lead author, said.

Blood thinners – used to prevent heart attacks and strokes – were the type of drug most associated with ADR-related hospitalizations among seniors, counting for 12.6 per cent.

Chemotherapy drugs were the second most-common cause, at 12.1 per cent. Opioids – a class of strong pain killers – caused around 7.4 per cent of hospitalizations among seniors.

The most-common adverse effect was bleeding as a result of blood thinners, which accounted for around one in eight hospitalizations, Jordan Hunt, CIHI’s manager of pharmaceuticals, said.

Other common adverse effects included low white blood cell count from chemotherapy drugs and constipation caused by opioids.

One of the factors associated with hospitalization was the number of drugs used by the patient.

Patients taking 15 or more drugs were six times more likely to have been hospitalized for an ADR, the report found. Patients taking 10 or more drugs were around four times more likely to be hospitalized.

The age of the patient was also a factor, Hunt said.

“Seniors are at greater risk because your body changes over time -- how it reacts to drugs and how it processes drugs. And that makes them more at risk for reactions and to harm from those reactions when they do occur,” he said.

ADRs are costly. One estimate found that ADRs cost the health-care system around $35.7 million a year, with 80 per cent of that cost stemming from hospital admissions.

CIHI says reviewing and managing medications can help reduce the number of ADRs that can result when a patient is using a high number of drugs.

Dr. David Juurlink, of the Institute for Clinical Evaluative Sciences in Toronto, agrees and says patients should review their medication lists with a doctor or pharmacist regularly.

“The next time you’re in to see your doctor you may want to bring your medication list and go through the medicines and say ‘Do I really need each of these?’” Juurlink said.

“The message for doctors, I think, is ‘We’re really good at starting drugs. We’re not very good at stopping drugs.’”

With a report by CTV’s medical specialist Avis Favaro and producer Elizabeth St. Philip and files from The Canadian Press