An analysis of tens of thousands of people in nursing homes in the U.S. suggests that residents who take certain antipsychotic drugs for dementia are at about double the risk of dying compared to residents not taking those specific medications.

All the residents in the study, published Friday in the British Medical Journal (BMJ), were over age 65.

The Harvard Medical School study, the largest ever undertaken among U.S. nursing home residents, focused on 75,445 nursing-home residents from 45 states from 2001 to 2005. Their risks of death were looked at during a six-month period.

The study notes that the U.S. Food and Drug Administration (FDA) warned in 2005 that atypical antipsychotic drugs — also known as second-generation antipsychotics —are associated with an increased risk of death in older people with dementia, but it wasn't know whether the risk depends on the type of drug the person is taking.

In 2008, the FDA expanded that warning to include conventional antipsychotics — also called neuroleptics — a class of drug used to relieve symptoms including hallucinations and delusions, and to calm very aggressive patients.

The Harvard researchers conclude that not all antipsychotic medication carries the same risk of death in older people, and "clinicians may want to consider this evidence when evaluating […] the best approach to treatment of behavioural problems." They also stress the importance of prescribing such drugs in the lowest possible dose, and closely monitoring patients shortly after they start treatment.

As the population ages, dementia — the progressive deterioration in cognitive function, or the ability to process thought — is becoming a very real concern. The Alzheimer Society of Canada, which is lobbying the Canadian government to create a plan to respond to concerns that more than 500,000 people have Alzheimer's or other dementia, with that number expected to double by 2038.

In the U.S., the number of people with some form of dementia is estimated at up to five million.

In the Harvard study, the antipsychotic drugs taken by nursing-home residents included:

Aripiprazole.

Haloperidol.

Olanzapine.

Quetiapine.

Risperidone.

Ziprasidone.

Out of the 75,445 residents, a total of 6,598 died within the six-month study from non-cancer related causes. Patients treated with haloperidol had double the risk of death compared to those taking risperidone, while those taking quetiapine had a reduced risk.

The effect of haloperidol was strongest during the first 40 days of treatment, and that did not change after the dosage was adjusted. Almost half of deaths (49 per cent) were recorded as due to circulatory disorders, 10 per cent due to to brain disorders and 15 due to respiratory disorders.

Besides age, gender and whether a patient had any physical illnesses or lived in a part of the U.S. that may raise their risk of death, the state of the nursing homes they were in — including their size, the occupancy rate, availability of special-care units and staffing levels — were taken into consideration.

The study was partially funded by U.S. National Institute of Mental Health, and researchers reported no funding or relationships with any organizations that may have influenced their work.

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Dementia death risk doubles on some antipsychotics