Risk factors

Risk factors for cognitive decline and dementia are similar, with the strongest risk factor being age. Other factors consistently associated with both cognitive decline and dementia include:

•   the APOE e4 allele
•   Head injury with loss of consciousness
•   risk factors for cardiovascular disease (diabetes, stroke, smoking, physical inactivity, high LDL cholesterol, obesity), and
•   low level of education.

Factors moderated by lifestyle may have an impact from midlife,  and possibly earlier.  The association between blood pressure and cognitive decline is complicated.  High blood pressure in midlife appears to increase the risk of cognitive decline   and in general hypertension is associated with an increased risk of vascular dementia and Alzheimer disease;  however, in adults over 75 years of age,  low diastolic blood pressure may increase the risk of dementia.

Protective factors
Factors that have been shown to have a protective effect against cognitive decline and dementia include:

• vitamin E
•   foods high in antioxidants and omega-3 fatty acids
•   mental and physical activity
•   social engagement, and
•   statins.

There is mixed support for the effect of oestrogen on cognitive decline.

Public health implications and directions for primary care
Latest research shows that lifestyle factors known to affect the risk of heart disease also affect the risk of developing ‘normal’ cognitive decline and dementia. Having a healthy heart in later life may also lead to a healthier brain due to reduction in the build up of cholesterol, increased perfusion, reduction in stroke and TIAs.  However, the impact of these factors is very slow, so prevention strategies need to be implemented in early and mid adulthood.

Encouraging patients to adopt a healthier and more active lifestyle will reduce what is presently viewed as normal cognitive decline in the population.