Register-based Prospective Cohort Study Research Articles

Bipolar Disorder, Schizoaffective Disorder, and Schizophrenia Overlap

Growing evidence of an etiologic overlap between schizophrenia, schizoaffective disorder, and bipolar disorder has become increasingly difficult to disregard. We investigated the magnitude of the overlap between the clinical diagnoses of bipolar affective disorder, schizoaffective disorder, and schizophrenia over a 35-year period based on the entire Danish population. We established a register-based prospective cohort study of more than 2.5 million persons born in Denmark after 1954. Risks for the 3 psychiatric disorders were estimated by survival analysis using the Aalen-Johansen method. Cohort members were followed from 1970 to 2006. We introduced a new comorbidity index measuring the magnitude of the overlap between the 3 disorders. Overall, 12,734 patients were admitted with schizophrenia, 4,205 with bipolar disorder, and 1,881 with schizoaffective disorder. A female bipolar patient's risk of also being admitted with a schizoaffective disorder by the age of 45 years was approximately 103 times higher than that of a woman at the same age in the general population. Thus, we defined the comorbidity index between schizoaffective disorder and bipolar disorder at age 45 years to be 103. At age 45 years, the index between schizophrenia and schizoaffective disorder was 80 and between schizophrenia and bipolar disorder was 20. Similar large comorbidity indexes were found for men. A large comorbidity index between schizophrenia and schizoaffective disorder was found, as well as a large index between bipolar disorder and schizoaffective disorder. But, more surprisingly, it was clear that a substantial comorbidity index between bipolar disorder and schizophrenia was present. This study supports the existence of an overlap between bipolar disorder and schizophrenia and thus challenges the strict categorical approach used in both DSM-IV and ICD-10 classification systems.

First car-to-car crashes involving young adult drivers: main patterns and their relation to car and driver characteristics

The primary objective of the study was to examine the relationship between patterns in car-to-car crashes involving young drivers and car and driver characteristics and the research design was a national register-based prospective cohort study. Individual records in a cohort born 1970 – 1972 are linked to road-traffic-crash data (1988 – 2000). Subjects' first police-registered two-car crash leading to severe or fatal injury (n = 4875) are identified. Typical crash patterns are highlighted and associations between pattern and both car and individual socio-demographic characteristics are tested. Four crash patterns are highlighted. Male drivers and those with lower educational attainment are over-represented in all patterns. Pattern-based risk levels vary considerably according to car safety level and driver's age at time of injury and socio-economic status. Crash patterns might be considered in young adult driver education systems, bearing in mind the consistent higher risks of male drivers and of drivers with lower educational attainment.