Risk of subsequent dementia among patients with bipolar disorder or major depression: a nationwide longitudinal study in Taiwan.
BACKGROUND
Both major depression and bipolar disorder are associated with an increased risk of developing dementia. However, the differential risk of dementia between major depression and bipolar disorder is rarely investigated.


METHODS
Using the Taiwan National Health Insurance Research Database, a total of 2291 patients aged ≥ 55 years (major depression: 1946 and bipolar disorder: 345) and 2291 age-and sex-matched controls were enrolled between 1998 and 2008, and followed to the end of 2011. Participants who developed dementia during the follow-up were identified.


RESULTS
Both patients with bipolar disorder [hazard ratio (HR) 5.58, 95% confidence interval (CI) 4.26-7.32] and those with major depression (HR 3.02, 95% CI 2.46-3.70) had an increased risk of developing dementia in later life, after adjusting for demographic data and medical comorbidities. The sensitivity tests after excluding the 1-year (bipolar disorder: HR 4.73, 95% CI 3.50-6.35; major depression: HR 2.62, 95% CI 2.11-3.25) and 3-year (HR 3.92, 95% CI 2.78-5.54; HR 2.21, 95% CI 1.73-2.83, respectively) follow-up duration also revealed consistent findings. Furthermore, patients with bipolar disorder were associated with an 87% increased risk (HR 1.87, 95% CI 1.48-2.37) of subsequent dementia compared with patients with major depression.


CONCLUSIONS
Midlife individuals with bipolar disorder or major depression were associated with an elevated risk of developing dementia in later life. Further studies may be required to clarify the underlying mechanisms among major depression, bipolar disorder, and dementia, and to investigate whether prompt intervention may decrease this risk.
Department of Psychiatry, Taipei Veterans General Hospital, Taipei, Taiwan; Department of Psychiatry, College of Medicine, National Yang-Ming University, Taipei, Taiwan.
Mu-Hong
MH
Chen
Department of Psychiatry, Taipei Veterans General Hospital, Taipei, Taiwan; Department of Psychiatry, College of Medicine, National Yang-Ming University, Taipei, Taiwan.
Cheng-Ta
CT
Li
Department of Psychiatry, Taipei Veterans General Hospital, Taipei, Taiwan; Department of Psychiatry, College of Medicine, National Yang-Ming University, Taipei, Taiwan.
Chia-Fen
CF
Tsai
Department of Psychiatry, Taipei Veterans General Hospital, Taipei, Taiwan.
Wei-Chen
WC
Lin
Department of Psychiatry, Taipei Veterans General Hospital, Taipei, Taiwan.
Wen-Han
WH
Chang
Department of Family Medicine, Taipei Veterans General Hospital, Taipei, Taiwan; Institute of Hospital and Health Care Administration, National Yang-Ming University, Taipei, Taiwan.
Tzeng-Ji
TJ
Chen
School of Traditional Chinese Medicine, Chang Gung University, Taoyuan, Taiwan; Research Center for Industry of Human Ecology, Chang Gung University of Science and Technology, Taoyuan, Taiwan; Liver Research Center, Chang Gung Memorial Hospital, Taoyuan, Taiwan.
Tai-Long
TL
Pan
Department of Psychiatry, Taipei Veterans General Hospital, Taipei, Taiwan; Department of Psychiatry, College of Medicine, National Yang-Ming University, Taipei, Taiwan. Electronic address: tomsu0402@gmail.com.
Tung-Ping
TP
Su
Department of Psychiatry, Taipei Veterans General Hospital, Taipei, Taiwan; Department of Psychiatry, College of Medicine, National Yang-Ming University, Taipei, Taiwan. Electronic address: ymbi@mail2000.com.tw.
Ya-Mei
YM
Bai
D000368:Aged; D000369:Aged, 80 and over; D001714:Bipolar Disorder / Q000453:epidemiology*; D003704:Dementia / Q000453:epidemiology*; D003865:Major Depressive Disorder / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D013624:Taiwan / Q000453:epidemiology
Bipolar disorder; dementia; major depression