Abstract
Background: Dementia is a significant public health concern, with up to 40% of cases potentially preventable through risk factor modification. Depression and cardiometabolic conditions are suggested as modifiable risk factors for dementia, but their relationship to dementia risk remains unclear.
Aim: This thesis investigated the role of depressive symptoms and cardiometabolic risk factors, including central obesity, low HDL cholesterol, systolic and diastolic blood pressure (BP), hyperglycaemia, diabetes, and increased inflammation, in the risk of dementia among older individuals in England, the US, and China.
Methods: Data were drawn from the English Longitudinal Study of Ageing, the Health and Retirement Study, and the China Health and Retirement Longitudinal Study. The analyses included 7,666 participants from ELSA (waves 2–9, 2004/05–2018/19), 6,735 from HRS (waves 8–14, 2006/07–2018/19), and 11,847 from CHARLS (waves 1–4, 2011/12–2018/19), aged 50 years or older at baseline.
Results: Depressive symptoms emerged as an independent risk factor for dementia, regardless of the presence of cardiometabolic factors, with individuals exhibiting increasing and chronically high depressive symptoms facing the highest risk across all three populations. Elevated systolic BP consistently demonstrated a significant association with dementia in all three countries. However, diabetes, hyperglycaemia, low HDL cholesterol, and increased inflammation showed country-specific associations with dementia risk. Through latent class analysis, distinct patterns of combined cardiometabolic risk factors, including a complex cardiometabolic cluster in Western countries and an obesity-hypertension cluster in China, showed an increased dementia risk. Cardiometabolic risk appeared to precede depressive symptoms and dementia development, with depression serving as a potential pathway linking cardiometabolic health to dementia.
Conclusion: This research provides evidence concerning the causal and temporal associations between depressive symptoms, cardiometabolic risk factors and dementia development. Culturally-sensitive interventions for the early identification and treatment of depressive symptoms and cardiometabolic comorbidities suggest a promising approach to addressing the growing burden of dementia in Western and non-Western countries.