Abstract
BackgroundThe exploration of adverse health outcomes and chronic health conditions in military veterans is essential in occupational epidemiology to identify gaps in public health needs. Recent demographic reports in the UK showed a higher proportion of military veterans were in the 65 years and over category than non-veterans. Additionally given that military veterans are at risk of mental and physical ill-health and lifestyle-related factors (including depression, post-traumatic stress disorder, traumatic brain injury (TBI), diabetes, heart disease, high cholesterol, high blood pressure, stroke, obesity, cigarette smoking, frequent alcohol consumption, and being physically inactive), the risk of Mild Cognitive Impairment (MCI) is probable and warrants further exploration. Previous research has investigated the association between the aforementioned mental and physical health disorders, lifestyle-related factors, and dementia in the military and non-veteran populations in the UK. Although research is yet to compare the risk of MCI in UK military veterans and non-veterans using data from a single study which is essential for making direct comparisons.
Aims
This thesis aimed to address this gap by using data from a single UK-based study to investigate the association between mental and physical ill-health status, lifestyle-related factors, and MCI. This was done in three main analysis: (a) comparing the risk of MCI in individuals with or without the aforementioned risk factors in the overall sample, (b) comparing the risk of MCI only in military veterans and non-veterans with the aforementioned risk factors, (c) comparing the risk of MCI in military veterans with or without the aforementioned risk factors.
Methods
A series of epidemiological analyses was conducted to address the aim of this thesis. A systematic review and meta-analysis explored the association between the aforementioned health risk factors and MCI and dementia in military veterans. Based on the findings from the systematic review and meta-analysis, a deep dive analysis was conducted utilising data from the PROTECT study, a cohort study exploring healthy brain ageing, cognitive decline, and MCI in middle-aged and older adults (≥40 years) in the UK. This included analysis from two prospective cohort studies and a cross-sectional study investigating the association between MCI and (1) depression, (2) cardiovascular health (CVH) and lifestyle-related risk factors, and (3) lifetime TBI.
Results
Findings from the systematic review and meta-analysis, which included 25 peer-reviewed articles, showed over two-thirds of existing research were based on dementia in military veterans. Depression, TBI, and obesity were significantly associated with cognitive decline in military veterans. The meta-analysis showed depression (OR = 2.45, 95% CI 1.37-4.36), PTSD (OR=1.86, 95% CI 1.56-2.21) and TBI (OR=2.05, 95% CI 1.68-2.50) significantly increased the risk of dementia in military veterans.
A prospective cohort analysis was conducted using data from the PROTECT study which comprised of military veterans and non-veterans. Depression significantly increased the risk of MCI (HR=2.45, 95% CI 2.03-3.01) in the overall sample. There was no significant difference in the risk of MCI between military veterans and non-veterans with depression (HR=0.56, 95% CI 0.24-1.30) and between military veterans with or without depression (HR=1.85, 95% CI 0.67-5.12).
The next prospective cohort analysis explored the association between nine CVH and lifestyle-related risk factors and MCI in a sample of military veterans and non-veterans. The risk of MCI significantly reduced in military veterans who were obese (HR=0.21, 95% CI 0.07-0.65), frequent alcohol consumers (HR=0.53, 95% CI 0.38-0.74), or physically inactive (HR=0.46, 95% CI 0.25-0.85) compared to non-veterans. There was a significant difference in the risk of MCI between military veterans with diabetes (HR=2.22, 95% CI 1.04-4.75) or high cholesterol (HR=3.11, 95% CI 1.64-5.87) compared to military veterans without diabetes or high cholesterol.
A cross-sectional analysis was conducted which comprised of military veterans and non-veterans. TBI significantly increased the risk of MCI (OR=1.21, 95% CI 1.11-1.31) in the overall sample. There was no significant difference in the risk of MCI between military veterans and non-veterans with TBI (OR=1.19, 95% CI 0.98-1.45) and between military veterans with or without TBI (OR=1.21, 95% CI 0.83-1.74).
Conclusion
In summary, the risk of MCI was driven by mental and physical health and lifestyle-related risk factors and not by military veteran status except for obesity, alcohol consumption and physical inactivity. Within the military veteran sample, diabetes and high cholesterol increased the risk of MCI. This thesis highlighted the importance of understanding risk factors associated with MCI in UK military veterans. These findings have clinical, social, occupational and research implications. Future research is needed to explore other health risk factors, subtypes of MCI and the military job profile of military veterans.
| Date of Award | 1 Dec 2023 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Neil Greenberg (Supervisor) & Sharon Stevelink (Supervisor) |