Sustained attention deficit a potential endophenotye for bipolar disorder
MedWire News: Researchers suggest that sustained attention deficit is an endophenotype for bipolar disorder that is maintained during asymptomatic states.
They also report that this deficit occurs independently of clinical severity, defined by psychotic history and number of episodes and hospitalizations.
The team, led by Jose Antonio Cabranes, from Clinico San Carlos Hospital in Madrid, Spain, used the Continuous Performance Test (DS-CPT) to evaluate sustained attention in 143 euthymic patients with bipolar disorder and 105 mentally healthy controls.
The test involves six blocks of 80 trials in total, taking approximately 8 minutes to complete. These six blocks are then combined into three blocks of 160 trials, which allow the study of early, middle, and late attention stages. Performance on the test was analyzed by "accuracy" measures (correct responses and false alarms), efficiency measures (reaction time), and measures derived from signal detection theory (sensibility and response criterion).
Patients with bipolar disorder had fewer hits, longer reaction times, and lower sensibilities than controls in all blocks.
In block 1, 8.5% of bipolar disorder patients scored below the fifth percentile of the control group, signifying a global clinical significant deficit in sustained attention, while in blocks 2 and 3, 8.9% and 11.7% of patients scored below the fifth percentile, respectively.
For both patients and controls, sustained attention worsened with increasing age and improved with years of education and premorbid IQ.
After controlling for these factors in regression analysis, the researchers found that sustained attention performance in bipolar disorder patients correlated significantly with age of illness onset, age of first hospitalization, and duration of illness, but not with severity of illness.
The researchers also point out in the journal Acta Psychiatrica Scandinavica that sustained attention tended to be worse in patients who were unemployed.
"It is therefore possible that cognitive alterations might worsen patients' life quality and functioning, including employment and productivity at work," they say.
Cabranes and team add that further research is needed to determine if sustained attention disturbances are present from the onset of illness and become more obvious as the disorder progresses, and if they are modified by medication.
"These studies would also help to clarify the stability of the deficit, the last criteria that an endophenotype should satisfy," they conclude.
MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010
By Lucy Piper