New York, Jan 5
Having bipolar disorder -- a serious mental illness that can cause both manic and depressed moods -- increases the risk of dying early, more than smoking.
Researchers from the University of Michigan in the US analysed how large the risk of death among people with bipolar disorder -- who smoked and those who had never smoked.
The results, published in the journal Psychiatry Research, showed that people with bipolar disorder were four to six times more likely as people without the condition to die prematurely, the study finds.
By contrast, people who smoked were about twice as likely to die prematurely than those who had never smoked -- whether or not they had bipolar disorder.
The stark difference in mortality, and the differences in health and lifestyle that likely contributed to it, should prompt more efforts at preventing early deaths, the researchers said.
"Bipolar disorder has long been seen as a risk factor for mortality, but always through a lens of other common causes of death," said lead author Anastasia Yocum, from the varsity.
"We wanted to look at it by itself in comparison with conditions and lifestyle behaviours that are also linked to higher rates of premature death."
The team started by looking at deaths and related factors among 1,128 people with and without bipolar disorder.
They found that all but 2 of the 56 deaths since the study began in 2006 were from the group of 847 people in the study who had bipolar disorder.
The researchers then turned to another source of data to see if they could find the same effect.
They analysed anonymous patient records from more than 18,000 people.
Among these, people with bipolar disorder were four times as likely to die than those with no record of bipolar disorder.
The team also studied records from more than 10,700 people with bipolar disorder and a comparison group of just over 7,800 people without any psychiatric disorder.
The only factor associated with an even higher chance of dying during the study period in this pool of people was high blood pressure.
Those who had hypertension were five times more likely to die than those with normal blood pressure, no matter whether they had bipolar disorder or not.
By contrast, smokers were twice as likely to die as never-smokers in this sample, and those over age 60 were three times as likely to die, both regardless of bipolar status.
"To our major surprise, in both samples we found that having bipolar disorder is far more of a risk for premature death than smoking," said McInnis, a professor of psychiatry at the varsity's Medical School.
He hopes the findings will spur more action in the medical and public health communities to address the many factors that contribute to this extra-high risk of death in people with bipolar disorder.