This large national cohort study allowed the identification of several risk factors for suicide in dementia that are consistent with findings of previous research. Risk factors for suicide in dementia previously described include depression and younger age (9
). As anticipated, we found comorbid depression to be associated with substantially increased suicide risk. In contrast, comorbid schizophrenia was found to be a potentially protective factor among elder with dementia. Our results further suggest that the majority of suicides were among patients receiving psychiatric treatment. Additionally, patients who committed suicide in our study were younger than those who did not, and the majority of suicides appeared to occur in those with new dementia diagnoses. However, unlike many prior studies, concurrent medical comorbidities were not found to increase risk. While prior work regarding suicide and self-injurious behaviour in nursing homes has been inconclusive, we found a decreased risk of suicide in patients with nursing home admissions. In terms of methods of committing suicide, the vast majority of patients with dementia took their lives using a firearm (73%).
Patients in our study who died by suicide were younger than those who did not. This is consistent with previous research in the VA population (18
) but at odds with epidemiological observation in the general population over age 60 years, in which risk for suicide in men rises continuously through old-old age. In this sample of veterans with dementia, the greater risk with young-old age could reflect several factors. Those with earlier onset Alzheimer’s type dementia may have a more aggressive, neuropsychiatrically complex illness. Younger age of onset carries a higher likelihood of a family history of dementia which may influence the patient’s outlook on the future. There is growing evidence that depression and anxiety are more likely to occur early in the course of dementia (19
). Anxiety related to the diagnosis of dementia at an earlier age may drive suicidal behaviour.
The relationship between depression and later-life suicide is well established. (20
) Perhaps not surprisingly, the individuals in this study who died by suicide were significantly more likely to have been diagnosed with depression. Prescription of an antidepressant was as strong a predictor as having a diagnosis of depression. Interestingly, however, more patients were prescribed antidepressants than actually carried the diagnosis of depression. The difference between the number of patients with a depression diagnosis (27,079 total in cohort) and those prescribed antidepressants (91,142) may represent either an underreporting of depression diagnoses or may represent the prescription of antidepressants for reasons other than affective disorder, such as pain or sleep
Prescription of an anti-anxiety medication was also a strong predictor of suicide. Recent work by Pfeiffer et al. (21
) found co-morbid anxiety disorders and fills of an anti-anxiety medications was associated with suicide risk among a mixed aged cohort of depressed patients. They also found that prescription of an anti-anxiety medication was a stronger predictor of completed suicide than any anxiety diagnosis consistent with our findings. As expected, we found that patients who died from suicide were far more likely to have had psychiatric care (both inpatient and outpatient). Given that a number of patients with dementia and neuropsychiatric symptoms might not receive a separate comorbid psychiatric diagnosis, our findings suggest that those dementia patients with accompanying neuropsychiatric symptoms (indicated either by an accompanying diagnosis of depression or receipt of antidepressants or anxiolytics) are at higher risk for suicide than those with cognitive symptoms only.
In contrast to many prior studies, concurrent medical comorbidities were not found to increase suicide risk. In perhaps the largest study of this issue, Waern et al. (22
) found that serious physical illness was independently associated with suicide in elderly people. Conwell et al. (4
) recently reported similar findings, noting that physical illness and associated functional impairments were more common in older adults who committed suicide. However, a limitation of this study is that we were unable to assess the impact of disability resulting from medical comorbidities which represents a potential confounder in the medical comorbidity-suicide relationship.
A noteworthy finding in our study was that the majority (75%) of suicides occurred in those with a new dementia diagnosis. This finding would seem to confirm both the conventional wisdom as well as limited research (6
) that the most significant concern for suicide in dementia is early in the course of illness. Placed in this context, our finding that a history of nursing home care decreased the likelihood of suicide significantly could be expected. Although data concerning suicidal behaviour in nursing home residents is limited and contradictory (23
), the very structured, supervised nature of such facilities and the limited access to firearms may limit suicidal behaviours. It is also possible that this group of patients represents those with more severe cognitive and/or physical limitations who would thus have more difficulty preparing and executing a suicide plan. Similarly, we found that a diagnosis of schizophrenia, an illness also associated with executive and planning deficits, was potentially protective.
Several limitations are inherent in the use of registry data. Given the VA population, the cohort was primarily male, and the study results may not be generalizable to other populations. Because registry dementia diagnoses are clinical, cases not yet diagnosed with dementia (likelier earlier cases where the risk of suicide may be the greatest) cannot be ascertained. However, our definition of “dementia” was purposefully inclusive in order to capture as many early cases as possible. A final limitation of our study is the use of a proxy as an indicator of dementia severity, i.e. time since dementia diagnosis. To the extent that this might not be an adequate proxy, our analyses must be interpreted with caution. However, given that the existing literature suggests that suicide is an uncommon event in patients with dementia, and that recruiting the large numbers of patients with mild cognitive impairment and dementia necessary for prospective, longitudinal studies may be difficult, large registry studies such as ours are important to address potential risk factors.
At present, our findings suggest that patients with accompanying neuropsychiatric symptoms of depression and anxiety in psychiatric treatment who are early in their course of dementia are at greatest risk for suicide. Timely identification and intervention addressing the complex issues of depression and dementia in these patients may help to mitigate their increased risk. Our findings also support the growing evidence that restricting access to firearms is one of the most effective strategies for suicide prevention.(25
) Given the high rate of suicide by firearms, closer monitoring and assessment of access to firearms may be an essential part of treatment planning for older male patients with dementia.