Competing risk analysis of the association between dementia and major depressive disorder: a nationwide population-based study in Taiwan

The relationship between major depressive disorder and dementia: A bidirectional two-sample Mendelian randomization study

BACKGROUND

Major depressive disorder (MDD) and dementia psychiatric and neurological diseases that are clinically widespread, but whether there is a causal link between them is still unclear. In this study, bidirectional two-sample Mendelian randomization (MR) was used to investigate the potential causal relationship between MDD and dementia via a genome-wide association study (GWAS) database, containing samples from the European population.

METHOD

We collected data on MDD and common clinical dementia subtypes from GWAS, including Alzheimer's disease (AD), frontotemporal dementia (FTD), dementia with Lewy bodies (DLB), Parkinson's disease with dementia (PDD), and vascular dementia (VaD). A series of bidirectional two-sample MR studies and correlation sensitivity analysis were carried out.

RESULTS

In the study of the effect of MDD on dementia subtypes, no causal relationship was found between MDD and dementia subtypes other than VaD, inverse variance weighted (IVW) method: odds ratio (OR), 2.131; 95 % confidence interval (CI), 1.249-3.639, P = 0.006; MDD-AD: OR, 1.000; 95 % CI, 0.999-1.001, P = 0.537; MDD-FTD: OR, 1.476; 95 % CI, 0.471-4.627, P = 0.505; MDD-PDD: OR, 0.592; 95 % CI, 0.204-1.718, P = 0.335; MR-Egger method: MDD-DLB: OR, 0.582; 95 % CI, 0.021-15.962, P = 0.751. In reverse MR analyses, no dementia subtype was found to be a risk factor for MDD.

LIMITATIONS

The results of this study may not be generalizable to non-European populations.

CONCLUSION

MDD was identified as a potential risk factor for VaD, but no dementia subtype was found to be a risk factor for MDD. These results suggest a new avenue for the prevention of VaD.

Bidirectional association between major depressive disorder and dementia: Two population-based cohort studies in Taiwan

BACKGROUND

Major depressive disorder (MDD) and dementia are both major contributors to the global burden of disease. Despite existing literature on the association between MDD and dementia, there is a lack of a nationwide longitudinal cohort study that considers the competing risk of death. Therefore, this study assessed the bidirectional associations between MDD and dementia over an 11-year period in population-based settings, accounting for death as a competing risk.

METHODS

We conducted two population-based retrospective cohort studies in Taiwan. We identified 80,742 patients diagnosed with MDD in 2009-2010 and matched them with patients without MDD by sex, age, and year of diagnosis to assess the relative risk of dementia. We also identified 80,108 patients diagnosed with dementia in 2009-2010 and matched them with patients without dementia by sex, age, and year of diagnosis to assess the relative risk of MDD. All patients were followed until they received a diagnosis of new onset MDD or new onset dementia, their death, or the end of 2019. Cause-specific hazards models were used to estimate adjusted hazard ratios (aHRs).

RESULTS

The incidence density (ID) of dementia was higher in patients with MDD than in patients without MDD (7.63 vs. 2.99 per 1000 person-years), with an aHR of 2.71 (95% confidence interval [CI]: 2.55-2.88). The ID of MDD was higher in patients with dementia than in patients without dementia (12.77 vs. 4.69 per 1000 person-years), with an aHR of 2.47 (95% CI: 2.35-2.59).

CONCLUSIONS

This population-based study found a bidirectional association between MDD and dementia. Our findings suggest the need to identify dementia in patients with MDD and vice versa.

Depression and bone loss as risk factors for cognitive decline: A systematic review and meta-analysis

BACKGROUND

Depression is linked to Alzheimer's disease (AD) but it is unclear whether depression is also associated with cognitive decline in the preclinical phase and mild cognitive impairment (MCI). Previous meta-analyses have only investigated AD as an outcome without accounting for individuals showing cognitive decline that does not meet the diagnostic criteria for AD. Other potentially modifiable risk factors such as bone loss have also been less explored and there remains uncertainty around their temporal relationship with cognitive decline.

AIMS

To conduct a systematic review and meta-analysis investigating depression and bone loss as risk factors for subsequent cognitive decline.

METHODS

A comprehensive search strategy was developed and applied using four databases; MEDLINE Complete, Embase, PsycINFO and CINAHL Complete. The pooled summary effects were estimated as odds ratios with 95% confidence intervals using a random-effects model. The study protocol was registered with PROSPERO (ID: CRD42020159369).

RESULTS

A total of 75 longitudinal cohort studies were identified for meta-analysis, of which 70 examined the impact of depression on cognitive decline and five examined the impact of bone loss. Prior exposure to depression was found to be associated with cognitive score reduction (OR 1.33 95% CI 1.17, 1.51), MCI incidence (OR 1.52 95% CI 1.28, 1.79) and AD incidence (OR 1.79 95% CI 1.46, 2.2). Bone loss was also associated with the incidence of AD (OR=1.81 95% CI 1.28, 2.55).

CONCLUSIONS

Overall, the results support the hypothesis that depression is associated with subsequent cognitive decline. Bone loss was also found to be associated with AD incidence; however, due to the small number of studies, the results should be viewed with caution.