FROM JOURNAL OF AFFECTIVE DISORDERS
Both the incidence of bipolar disorder and the standardized mortality ratio of patients with bipolar disorder, compared with the general population, significantly increased, according to a Danish cohort study.
The study was of 15,334 patients with a first-ever diagnosis of bipolar disorder, according to the International Classification of Diseases (ICD)-10 criteria, between Jan. 1, 1995, and Dec. 31, 2012. Patients were followed until Dec. 31, 2012, or death, whichever came first. Data came from the Danish Psychiatric Central Research Register, a national electronic registry containing all psychiatric hospitalizations since 1969 and all psychiatric outpatient contacts and emergency room visits since 1995. Those diagnosed with schizophrenia subsequent to being diagnosed with bipolar disorder and patients who received one of several specific ICD-8 diagnoses before 1995 (when the ICD-8 was in use) were excluded.
Bipolar disorder became significantly more common, especially throughout the 2000s. The total incidence rate was 18.5/100,000 person-years (PY) in 1995 and, at its lowest, was 14.8/100,000 PY in 1997. The most recent and highest incidence of the disorder was 28.4/100,000 PY in 2012. Such findings represent a higher incidence of bipolar disorder than was found in studies conducted in England during the same period, according to Clara Reece Medici of Aarhus University Hospital, in Risskov, Denmark, and her colleagues.
Significantly more females than males were diagnosed with bipolar disorder, with 9,132 females and 6,202 males having suffered from the disease.
Mortality in patients with bipolar disorder was higher, compared with the general population, with the mean standardized mortality ratio (SMR) for patients with bipolar disorder vs. the general population having been 1.7. Deaths of the bipolar patients were mostly tied to natural causes, but as many as 9% of the bipolar patients committed suicide.
Another of the study’s findings was that age at diagnosis of bipolar disorder decreased by more than 10 years, with the average age at diagnosis having been 54.5 in 1995, compared with 42.4 in 2012. The researchers said increased awareness among clinicians may explain this, but that they will test whether “increased use of antidepressants and medication against [attention-deficit/hyperactivity disorder] in Denmark in the same time period may have contributed to unmasking a latent bipolar episode earlier.”
According to the researchers, “studies on lowering physical illlness in patients with bipolar disorder are needed to lower death by natural causes.”
Read the full study in the Journal of Affective Disorders ( doi:http://dx.doi.org/10.1016/j.jad.2015.04.032 ).
