Most people with dementia have Alzheimer's disease, but there are other forms of dementia, and one of these occurs in around 80% of individuals with Parkinson's, usually some years after diagnosis.
In 2011, Dr. Daniel Weintraub, senior author of the current study, and colleagues found that despite these warnings, there was little action to reduce prescriptions of antipsychotic for patients with Parkinson's.
The researchers compared 7,877 Parkinson's patients who received prescriptions for antipsychotic drugs at any time from 1999-2010 with a control group that did not use the drugs.
They matched participants for factors such as age, ethnicity, gender, years since diagnosis and presence of dementia.
Results showed that in the 180 days after starting antipsychotic drugs, the rate of mortality among those taking the drugs was 2.35 higher than among those who were not.
Those taking quetiapine had a 2.16 higher risk compared with no treatment; with risperidone, the risk was 2.46 times higher, with olanzapine, 2.79 times, and haloperidol was associated with a 5.08 times higher rate of mortality.
Overall, first-generation antipsychotics, such as haloperidol, appeared to entail a 50% higher relative risk of mortality than more recently developed antipsychotics - for example, risperidone and quetiapine.