Two new findings in the field of primary prevention for dementia and Alzheimer’s disease

Two new findings in the field of primary prevention for dementia and Alzheimer’s disease have recently been reported by a research group led by Professor Laura Fratiglioni at Karolinska Institutet: the first is that both high and low blood pressure increase the chances of developing dementia. The second is that an active and socially integrated lifestyle protects against dementia.

“These findings are not only of scientific relevance in the contribution they make to our understanding of the aetiology of Alzheimer’s disease and dementia, they also have important clinical implications,” says Professor Fratiglioni.

Professor Fratiglioni continues: “The proper control of blood pressure is recommended in the elderly with appropriate treatment of hypertension, but it is equally relevant to monitor and avoid low blood pressure levels.

Finally, elderly people and public health organisers should all take into account the importance of social integration and physical and mental stimulation for preserving healthy cognitive functioning in the elderly.”

Previous studies have shown that high blood pressure in midlife is associated with an increased risk of developing dementia and Alzheimer’s disease in late life.

However, studies investigating the link between dementia and blood pressure in late life have produced conflicting results. In a previous study, Karolinska Institutet researchers suggested that both high and low blood pressure may damage the cognitive abilities of the elderly (Qiu et al, Archives of Neurology 2003).

The new study conducted by Dr Chengxuan Qiu and published in Stroke, the Journal of the American Heart Association in 2004, found that a substantial drop in systolic blood pressure (the higher number in a blood pressure reading) predicted the onset of dementia in people with a systolic pressure of less than 160 millimetres of mercury (mm Hg). A drop in this pressure of 15 mm Hg or more was linked to a three-fold increase in the risk of developing Alzheimer’s disease and dementias.

These findings imply that poor blood flow in the brain, resulting from a serious drop in blood pressure, may trigger the dementia process. However, because so few studies have addressed the blood pressure decline–dementia connection, these findings need further verification.

This hypothesis has been explored by Professor Fratiglioni and her group since 2000 with relevant results already reported in The Lancet in 2000 and The American Journal of Epidemiology in 2002, such as 1) a 60 per cent increase risk of dementia in subjects with poor or limited social networks; and 2) a protective effect against dementia of engagement in social and mentally stimulating activities.

The new study reported in Lancet Neurology (June 2004) is a systematic review of this topic, where all studies examining the relation between social network and leisure activities and dementia or cognitive impairment have been analysed. Only those studies with an appropriate design were selected according to predetermined criteria: 15 observational longitudinal studies on cognitive impairment and 14 on dementia. Most of the observations (75 per cent) reported an association of one lifestyle aspect (engagement in social or mental or physical activities) with dementia and cognitive impairment.

These findings provide sufficient evidence that an active and socially integrated lifestyle may be beneficial in brain ageing by reducing cognitive decline and the risk of dementia. Several mechanisms may underline the reported associations from vascular to functional reserve and stress hypothesis.

These results were possible thanks to the databases available at Karolinska Institute’s Ageing Research Centre (ARC) where epidemiological research on ageing is one of the major research lines, and to the multidisciplinary organisation of this centre and the collaborative relationship there between different medical specialists, psychologists, and sociologists.

These new findings derive from the well-known epidemiological study called “The Kungsholmen Project on Ageing and Dementia”, which has been carried out in Stockholm since 1987 under the leadership of Professor Bengt Winblad of Karolinska Institutet’s Neurotec Department.

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