Abstract
Objective:
Metabolic disturbances and diagnosis of metabolic syndrome are more prevalent in patients with bipolar disorder than in general population. The underlying biological pathway regarding this high rate of metabolic syndrome compared to general population in bipolar disorder is still unknown. The side effect of second generation antipsychotics causing weight gain and insulin resistance is considered as one of the main factors. However, this knowledge is not sufficient to understand the association between bipolar disorder and metabolic syndrome entirely. The aim of this study is to investigate the seasonal variation in prevalence of the metabolic syndrome criteria and diagnosis in type 1 bipolar disorder.
Methods:
For this aim, 69 clinically remitted patients with type 1 bipolar disorder, who also met inclusion criteria for the study, were recruited. Metabolic syndrome was diagnosed by using the International Diabetes Federation (IDF) criteria. Young Mania Rating Scale and Hamilton Depression Rating Scale with 17 items were used in clinical interview in each visit to assess euthymia. All patients were followed up with four visits during one year, with one visit per each season. To investigate metabolic syndrome criteria, blood sampling, blood pressure and waist circumferences measures have been carried out. The data of 49 patients, who have been evaluated in all four visits and met inclusion- exclusion criteria in each visit, were analyzed. These data were used in investigation of the seasonal variation in the prevalence of metabolic syndrome criteria and metabolic syndrome diagnosis.
Results:
Of type 1 bipolar patients recruited to the study, the prevalence of metabolic syndrome diagnosis was 42.9%, 42.9%, 34.7% and 34.7% in winter, spring, summer and autumn, respectively. Although metabolic syndrome diagnosis was more prevalent in winter and in spring, the difference was not statistically significant. Of metabolic syndrome criteria, prevalence of low- HDL criterion, that was found lowest in spring, showed seasonal variation.
Discussion:
Although the results of this study do not support that the prevalence of metabolic syndrome diagnosis has a seasonal variation in type 1 bipolar patients, it shows that the prevalence of one of the metabolic syndrome criteria, low-HDL criterion, has seasonal variation among patients with bipolar disorder. Long term, large sample-sized follow-up studies are still required to investigate the seasonal variation in prevalence of metabolic syndrome criteria and metabolic syndrome diagnosis among patients with bipolar disorder. Metabolic syndrome, which is more prevalent in individuals with severe mental illnesses such as schizophrenia and bipolar disorder than in general population, is an important health issue considering its association with cardiovascular diseases, high mortality and morbidity rates. Clinicians should follow up metabolic changes as well as the mood changes among patients with bipolar

Key words: Bipolar disorder, metabolic syndrome, seasonality