A modern scourge
Dementia is an advancing modern scourge and has recently been reported to have overtaken coronary heart disease as the most frequent cause of death for women in the UK. For men, coronary heart disease remains the commonest.
There are a number of different types of dementia. The two most common are Alzheimer’s disease and vascular dementia, which between them make up 80 per cent of cases. About 47 million people in the world live with dementia and this number is projected to rise to about 130 million by 2050. The current figures for the UK are 850,000 rising to 2 million over that same period. About 10 per cent of over-65s have dementia and a further 20 per cent suffer mild cognitive impairment. Over the past five years there has been a large rise in the number of people with dementia admitted to hospital as emergencies. Many of them remain as inpatients for much longer than necessary because of a lack of social-care support in the community. In 2017–18 there were 379,000 such admissions, up 35 per cent over five years, and 40,000 of these remained in hospital for between 1 and 12 months.
Curiously, for any particular age group, dementia is getting less common. This is perhaps the result of a steady decline of vascular disease, with less smoking and better treatment of raised blood pressure and lipid levels. However, this effect is overwhelmed by the steady increase in the age of the population. Thus demented people are becoming more numerous, although not as numerous as might be expected.
There are several known contributors to the development of dementia. These include smoking, hypertension, obesity and that cause of so many problems – lack of exercise. About one third of dementia cases are attributable to these modifiable risk factors.
The devastation caused by this epidemic is hard to overstate, as the ill effects are seen in every aspect of our lives. Most families will sooner or later have to face the emotional, financial and social problems brought by a relative with dementia. The cost to the health service and to social services of this rising tide of dependence is astronomical. The Alzheimer’s Society has estimated that the cost to the nation is £24 billion annually. By 2025 this will rise to £32.5 billion and by 2050 it could be costing the UK economy £59.4 billion at today’s prices (Alzheimer’s Research UK, 2017). The economic impact of caring for each sufferer is currently some £28,500 per annum.
Exercise in the prevention of dementia
The evidence that dementia is delayed and reduced in severity by regular exercise is growing. Meta-analyses of all the prospective studies of the effects of midlife exercise have confirmed a significantly reduced risk of dementia and of milder forms of cognitive impairment in later life.
As an example, a recent study used the Swedish Twin Registry to identify 264 individuals with dementia. They were compared with 2,870 unimpaired controls, matched for age, sex and a number of other features. All were normal at baseline, with a mean age of 49, and were followed up for an average of 30 years. Compared with those who did virtually no exercise, those who performed light exercise had less than half the risk of developing dementia, while those who performed moderate exercise had one third the risk. A meta-analysis involving 164,000 subjects found a risk reduction of 28 per cent for dementia, and 55 per cent for Alzheimer’s, for those who were physically active. Higher levels of exercise are more protective and there is more evidence for the effectiveness of aerobic exercise than resistance training.
A major study in Korea, which included 62 286 participants, demonstrated that an increased physical activity level, including even light-intensity activity, was associated with a reduced risk of dementia in older adults.
A meta-analysis of 39 trials of all forms of exercise including aerobic exercise, strength training or a mixture of both involved nearly 13,000 individuals aged 50 or more. It found that there was a clear benefit to cognitive function from taking the usually recommended level of exercise needed for health gain. The conclusion was: ‘The findings suggest that an exercise programme with components of both aerobic and resistance-type training, of at least moderate intensity and at least 45 min per session, on as many days of the week as possible, is beneficial to cognitive function in adults aged more than 50 years’.
Cardio-respiratory Fitness and dementia prevention
Higher levels of physical fitness in mid-life are also associated with a lower risk of dementia in later life. Those in the upper 20 per cent for fitness have two thirds the risk of dementia compared with those in the lowest 20 per cent. A number of studies have confirmed that having a high level of physical fitness delays the onset of dementia by around a decade. The importance of cardiorespiratory fitness (CRF) rather than self-reported physical-activity (PA) level was emphasised by a study of nearly 7,000 subjects. It found that both CRF and PA are associated with quality of life over time, but only CRF was associated with preservation of cognitive function. This particularly applied to language ability, attention and processing speed.
An overall healthy lifestyle is clearly the best option for reducing the risk of developing dementia in old age. The more aspects of healthy behaviour that are adopted, the better will be the outcome. The Caerphilly Cohort Study looked at five different behaviours: exercise, maintaining normal weight, eating a healthy diet, not smoking and avoiding excess alcohol. It examined the rate of dementia over the following decades. Adhering to all five of these behaviours was associated with just one third the risk of dementia. Unfortunately, less than one per cent of subjects followed all five behaviours and only five per cent followed four out of the five behaviours. The biggest contributor to lowering the risk of dementia was regular exercise. This, on its own, reduced the risk by about 60 per cent.
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