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Risk factors

Risk factors for dementia include high blood pressure, hearing loss, smoking, obesity, depression, inactivity, diabetes, lower levels of education and low social contact. Over-indulgence in alcohol, lack of sleep, anemia, traumatic brain injury, and air pollution can also increase the chance of developing dementia. Many of these risk factors, including the lower level of education, smoking, physical inactivity and diabetes, are modifiable. Several of the group are known as vascular risk factors that may be possible to be reduced or eliminated. Managing these risk factors can reduce the risk of dementia in individuals in their late midlife or older age. A reduction in a number of these risk factors can give a positive outcome. The decreased risk achieved by adopting a healthy lifestyle is seen even in those with a high genetic risk.

In addition to the above risk factors, other psychological features, including certain personality traits (high neuroticism, and low conscientiousness), low purpose in life, and high loneliness, are risk factors for Alzheimer's disease and related dementias. For example, based on the English Longitudinal Study of Ageing (ELSA), research found that loneliness in older people can increase the risk of dementia by one-third. Not having a partner (being single, divorced, or widowed) can double the risk of dementia. However, having two or three closer relationships might reduce the risk by three-fifths.

The two most modifiable risk factors for dementia are physical inactivity and lack of cognitive stimulation. Physical activity, in particular aerobic exercise, is associated with a reduction in age-related brain tissue loss, and neurotoxic factors thereby preserving brain volume and neuronal integrity. Cognitive activity strengthens neural plasticity and together they help to support cognitive reserve. The neglect of these risk factors diminishes this reserve.

Sensory impairments of vision and hearing are modifiable risk factors for dementia. These impairments may precede the cognitive symptoms of Alzheimer's disease for example, by many years. Hearing loss may lead to social isolation which negatively affects cognition. Social isolation is also identified as a modifiable risk factor. Age-related hearing loss in midlife is linked to cognitive impairment in late life, and is seen as a risk factor for the development of Alzheimer's disease and dementia. Such hearing loss may be caused by a central auditory processing disorder that makes the understanding of speech against background noise difficult. Age-related hearing loss is characterised by slowed central processing of auditory information. Worldwide, mid-life hearing loss may account for around 9% of dementia cases.

Frailty may increase the risk of cognitive decline, and dementia, and the inverse also holds of cognitive impairment increasing the risk of frailty. Prevention of frailty may help to prevent cognitive decline.

There are no medications that can prevent cognitive decline and dementia. However blood pressure lowering medications might decrease the risk of dementia or cognitive problems by around 0.5%.

Economic disadvantage has been shown to have a strong link to higher dementia prevalence, which cannot yet be fully explained by other risk factors.