[Bipolar I disorder in France: prevalence of manic episodes and hospitalisation-related costs].
Bipolar disorder is a chronic, highly disabling illness. However, few studies have evaluated the economic impact of this illness. The objective of this study was to estimate: 1) the annual number of manic episodes in patients with bipolar I disorder, and 2) the costs of hospitalisations related to manic episodes in France. We only included data on bipolar I disorder, as there is greater consensus and better documentation for this subgroup of patients with bipolar disorder. The prevalence of manic episodes was estimated using published epidemiological data. A computerised literature search was performed using the traditional scientific and medical databases. Additional epidemiological references were identified from published studies and textbooks. For hospitalisation data, we used the statistics of the Medical Information Department of a large psychiatric hospital in Paris for the year 1999. We estimated the annual number of manic episodes in France based on: 1) the lifetime prevalence of bipolar I disorder, 2) the average cycle duration, 3) the proportion of rapid cycling patients, and 4) the proportion of depressive vs. manic episodes for patients with bipolar I disorder. In order to estimate the prevalence of bipolar I disorder, we conducted a random effects meta-analysis using published international data. Results of the meta-analysis, which was based on a total of 62 736 patients, showed the lifetime prevalence of bipolar I disorder to be 0.82% [95% CI: 0.42, 1.21]. Applied to the adult population in France, this prevalence implies that the number of persons who have ever experienced a bipolar I -disorder is approximately 390,000 [95% CI: 200,000, 575,000]. Few studies provide information on the duration of cycles in patients with bipolar I disorder. Available estimates suggest the cycle duration to be approximately 12 months. Regarding the proportion of rapid cyclers, data from the meta-analysis by Tondo et al. show that 18% of patients with bipolar disorder experience at least four episodes of mood disorder per year. Finally, based on findings provided by cohort studies, the number of depressive episodes appears to be roughly equal to the number of manic episodes during the course of bipolar disorder. A rapid cycling rate of 18% and a cycle duration of 12 months imply that, on average, among 100 bipolar patients, 18 will have a 3-month cycle duration and 82 a 14-month cycle duration. Given an equal proportion of manic and depressive episodes, the annual number of manic episodes would then be 68 for a cohort of 100 bipolar patients (0.68 episode per patient per year). Applying this figure to the estimate of the total number of patients with bipolar I disorder in France suggests that the annual number of manic episodes in France is 265,000 [95% CI: 136,000, 391,000]. Based on data from a psychiatric hospital in Paris, the proportion of manic episodes that require hospitalisation was estimated to be around 63% with an average length of stay of 32.4 days. Hence the annual number of hospitalisations for manic episodes in France is estimated to be 167 000 [95% CI: 86 000, 246 000] and the hospitalisation-related costs 1,3 billion euros approximately. Our review of literature highlights the lack of medical and economic data at the national level on the frequency and hospitalisation-related costs of manic episodes in patients with bipolar I disorder in France. Given the lifetime prevalence of bipolar I disorder which may be as high as 3% among adults, further studies are required in order to provide representative national data and to allow economic evaluations of costs related to bipolar disorder in France.