Seniors with diabetes were more vulnerable to sudden worsening of their glucose control when anti-psychotic treatment started. (CBC)

Seniors with diabetes who take anti-psychotic medications to control symptoms of dementia may have an increased risk of ending up in hospital, a Canadian-led study suggests.

In Monday's issue of the Archives of Internal Medicine, researchers reported they found seniors newly treated with an anti-psychotic medication were more likely to be hospitalized for hyperglycemia, or high blood sugar, compared with those who were not taking the drugs.

People with diabetes were more vulnerable to sudden worsening of their glucose control when the anti-psychotic treatment started, said the study's principal investigator, Dr. Lorraine Lipscombe, an endocrinologist at Women's College Hospital in Toronto.

After the first prescription for an anti-psychotic, the researchers said they found a six- to 15-fold rise in hospitalizations for high blood sugar, compared with those who were untreated with an anti-psychotic.

"This is particularly significant for the elderly because they are the biggest group of patients with diabetes and are already the most vulnerable to poor diabetes control," said Lipscombe, who is also a researcher at the Institute for Clinical Evaluative Sciences in Toronto.

The study looked at data on 13,817 diabetics in Ontario, aged 66 and older, who started antipsychotic treatment between 2002 and 2006. Participants were followed for an average of two years, and were compared with up to 10 controls of the same age and sex who were not hospitalized over the same time period.

The team compared the likelihood of hyperglycemia among those who were currently taking antipsychotic medications with those who had discontinued the medications for more than 180 days.

Of the total number of diabetics studied, 1,515 (11 per cent) were treated in hospital for hyperglycemia.

Family should watch for signs of rising blood sugar

"It doesn't mean that people shouldn't be treated with these drugs, it means that people need to be aware and monitored closely so they can avert hospitalization," Lipscombe said.

The researchers also suggested health-care providers consider options for managing behavioural symptoms of dementia among seniors with diabetes.

Lipscombe said family members and health-care providers should keep a close eye on a diabetic with dementia for signs of rising blood sugar, such as:

• Lack of appetite.
• Increased thirst and urination.
• Confusion.
• Lower levels of consciousness.

The findings suggested that the start of anti-psychotic therapy represents a critical period during which seniors with diabetes are particularly vulnerable to failure of the metabolic system, the researchers said.

Safety warnings

Both newer, or "atypical" anti-psychotics such as olanzapine, risperidone and quetiapine, as well as typical anti-psychotic drugs seemed to increase blood sugar levels.

Some atypical anti-psychotics carry safety warnings about increased risk of stroke and death among older people taking the medications.

It was thought that since the drugs can cause weight gain, the excess weight might lead to diabetes and high blood sugar levels. But in this study, the effect seemed to happen too quickly for that explanation to be likely, the researchers said.

Another possibility is that first-time users of anti-psychotic medications may experience an acute disruption in levels of the neurotransmitter dopamine, which also helps regulate blood sugar levels. The researchers called for more study to see whether a cause-and-effect relationship exists and to identify how it may occur.

The study was supported by funding from the Canadian Institutes for Health Research.

None of the study's authors are currently employed by pharmaceutical companies, but one previously worked for Bayer Inc. Another study author reported receiving research support and speaker's fees from several pharmaceutical companies.

With files from The Canadian Press