Research reportAntidepressants and dementia
Introduction
Studies suggest that depressive disorder is associated with increased risk of developing cognitive dysfunction (Kessing, 1998, Castaneda et al., 2008) and eventually dementia (Kessing et al., 1999, Kessing and Nilsson, 2003, Ownby et al., 2006) and that this risk increases with every new affective episode (Kessing, 1998, Kessing and Andersen, 2004). On the other hand, antidepressants may have neuroprotective abilities by increasing the proliferation of neural progenitors in the subgranulate zone of the hippocampus as well as the survival of these newborn neurons (Dranovsky and Hen, 2006, Banasr and Duman, 2007) and therefore improve memory processes and cognition (Schmitt et al., 2006). Further, it has been suggested that treatment with an SSRI may improve cognitive function and daily living in patients with Alzheimer's dementia (Mowla et al., 2007). However, the association between antidepressant consumption and the risk of developing dementia has never been investigated. It would be difficult to undertake a prospective longitudinal and controlled study investigating this association as a large number of patients with depression without symptoms on dementia and with and without antidepressant treatment would had to be followed longitudinally for at least 5–10 years. An alternative approach is to use register-based data as done in the present study. We hypothesized that continued treatment with antidepressants decreases the risk of developing dementia.
The aim of the present study was to investigate whether continued treatment with antidepressants is associated with reduced risk of dementia by linkage of Danish nation-wide registers of all prescribed antidepressants and all diagnoses of dementia given at hospital in- or outpatient settings in Denmark. It was hypothesized that 1) the use of antidepressants is associated with increased risk of dementia (as depressive disorder is associated with dementia) 2) continued treatment with antidepressants is associated with a decreased risk of developing dementia and further that 3) the risk of dementia decreases with the number of prescriptions of antidepressants.
Section snippets
The registers
Data were obtained by linking Danish population-based registers using the unique personal identification number, which is assigned to all 5.3 million persons living in Denmark, thus ensuring accurate linkage of information between registers, irrespective of changes in name etc. (Malig, 1996). In this way, the Medicinal Product Statistics (Danish National Board of Health, 2002) was linked with the Danish Medical Register on Vital Statistics (Juel and Helweg-Larsen, 1999), the Danish National
Results
During the study period from January 1, 1995 to December 31, 2005 a total of 1,467,383 persons who were older than 40 years were included in the study. Among the included persons, 687,552 persons purchased antidepressants at least once (exposed) and 779,831 persons did not purchase antidepressants (unexposed) according to data from the Medicinal Product Statistics. Characteristics of persons exposed and unexposed to antidepressants can be seen from Table 1. Table 2 shows the use of various
Discussion
This is the first study investigating the association between continued treatment with antidepressants and the risk of subsequently developing dementia. We confirmed our first hypothesis but not, or only partly, our second and third hypotheses, i.e., 1) the use of antidepressants was associated with increased risk of dementia but 2) continued treatment with antidepressants was not systematically associated with a decrease in the risk of developing dementia and 3) the risk of dementia did not
Role of funding source
Nothing declared.
Conflict of interest
No conflict declared.
Acknowledgement
Lars Vedel Kessing had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
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