Mortality Rate for Bipolar Disorder Has Increased in Denmark Since the 1990s

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Younger individuals may be more at risk for death by suicide, and in older patients, elevated levels of metabolic syndrome may lead to higher rates of death from heart disease.
Younger individuals may be more at risk for death by suicide, and in older patients, elevated levels of metabolic syndrome may lead to higher rates of death from heart disease.

The findings of a study in Bipolar Disorders indicate a gradual increase in the mortality rate of Danish people with bipolar disorder over a period of 20 years. The mechanisms behind this phenomenon are unclear.

The authors looked at data from all patients registered with a bipolar diagnosis between 1965 and 2014 in the Danish Psychiatric Research Registry, with linked information on deaths available from the Danish Civil Registration System. Of 6,176,414 people, 27,281 were diagnosed according to the International Classification of Diseases criteria. Analyses were conducted for mortality between 1995 and 2014 and included patients up to 65 years of age.

Compared with the general population, the overall standardized mortality ratio over 2 decades was 2.8 (95% CI, 2.8-2.9). More surprisingly, linear regression revealed a 0.03 year-over-year increase in the standardized mortality ratio (P <.01). Sex did not have a significant effect on these findings, but excess mortality was more prevalent in younger patients.

Although the study could not account for the reasons behind this increase, the authors pointed to other studies on mortality and bipolar disorder. Younger individuals may be more at risk for death by suicide, especially in the years following diagnosis. For older patients — perhaps because of socioeconomic differences and compromised quality of life — elevated levels of metabolic syndrome may lead to higher rates of death from heart disease.

Moreover, it is possible that the increase in life expectancy in the European Union — up 11.8 years since the 1960s — may have compounded this difference.

The authors used few exclusion criteria, and therefore, they noted that their findings are highly generalizable. At the same time, they noted, analyses were only adjusted for sex and age, so it is possible that other confounders exist.

Reference

Hansen PS, Laursen MF, Grøntved S, Straszek SPV, Licht RW, Nielsen RE. Increasing mortality gap for patients diagnosed with bipolar disorder—A nationwide study with 20 years of follow-up [published online July 26, 2018]. Bipolar Disord. doi:10.1111/bdi.12684

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