Alzheimer’s disease (AD) is the most common form of dementia. It affects the hippocampus, a region of the brain that plays an important role in memory and learning. As the hippocampus is damaged by AD, symptoms of memory loss occur – typically starting mildly and gradually worsening as the disease progresses. One person is diagnosed with AD every 60 seconds and the worldwide prevalence of AD is expected to increase dramatically from today’s 36 million to 108 million by the year 2050. Currently, patients live on average 8 years after AD diagnosis. AD is fatal 100% of the time and, as of yet, there is no successful cure.
The biological level ageing results from the impact of the accumulation of a wide variety of molecular and cellular damage over time. But these changes are neither linear nor consistent, and they are only loosely associated with a person’s age in years. There is no ‘typical’ older person and some 80 year-olds have physical and mental capacities similar to many 20 year-olds.
However, as we grow older our bodies are changing. We may grow a little rounder around the waistline, or wake in the night, or feel a little stiffer in the morning. Most of us have to start to use glasses, and slowly our hear turns grey. Some even loose it. As we grow older increased forgetfulness that not is impairing our daily life is considered to be a part of the normal aging process. Generally, information processing also slows as we grow older, and older people have more trouble multitasking. However, research find that problems with memory, language, thinking and judgment that are greater than normal age-related changes, also called cognitive impairment may increase the risk of later progressing to dementia. Still, some people with mild cognitive impairment never get worse, and a few eventually get better.
Most people know that exercise is good for their physical health, but not everyone knows that it also has beneficial effects for cognitive functions and mental health. Cognitive performance decreases with old age, and a growing elderly population increases the amount of people that will get diseases such as dementia and Alzheimer’s. In addition, mood related disorders are a major worldwide problem. Exercise can improve the lives of people who are at the risk of developing these brain-associated disorders.
Exercise can increase your memory
A study performed on elderly people showed that increased physical activity resulted in an enhanced memory performance. It did not matter if the increased activity came from organized training sessions or from routines embedded into the daily life such as walking to the supermarket, take the stairs instead of the elevator, and generally move around more in the house. One of the symptoms of diseases such as dementia and Alzheimer’s is impaired memory, and regular aerobic exercise is therefore recommended to prevent or delay the onset of these diseases.
It is well known that regular physical activity is a strong protective factor against numerous diseases. But as we have previously suggested, exercise may also mean gain for the brain, in terms of physical activity changing brain structures detected by MR imaging. A recently published study from Rotterdam followed 4406 elderly persons aged 61-97 (mean age 73 years) over a follow-up period up to 14 years, to examine the association between level of physical activity and risk of dementia. Physical activity was measured using self-reporting questionnaires. During 38 631 person-years, 583 participants developed dementia, and analysis showed a significant association between higher physical activity level and lower risk of dementia.
The same relation was found in a review of 16 clinical studies: physical activity seems to have a strong protective effect against dementia. It has to be noted, though, that almost all these studies used self-report questionnaires to assess physical activity. Even though these questionnaires were validated, there is always some uncertainty associated with self-report, for instance regarding recall bias, especially in older people. Measuring physical activity directly is however challenging due to time and costs, especially in larger samples like these. And just because the samples are large, we can still see a trend in spite of this uncertainty.
Physical activity only had a short-term protective effect (<4 years) against dementia in the Rotterdam study. This can be explained by the natural effect of aging on physical activity level, as the mean age was rather high (73 years) in this sample. A Swedish/Finnish study published in Lancet (2005) studied the same issue, but with middle-aged participants (mean age 50 years). They found that a high level of physical activity in mid-life even had a long-term protective effect against dementia and Alzheimers disease.
How can this association be understood? There are many theories. For instance, a study published in JAMA (2005) found that obesity in midlife (BMI>30) was associated with a greater risk of developing dementia later in life. Combined with cardiovascular risk factors often following obesity, like high total cholesterol level and hypertension, the risk increased additively. We know that physical activity protects against these risk factors – indicating that being active throughout the whole life span is of great importance.
But how much exercise is needed to keep a healthy brain? The results are inconclusive here and future research will have to target this. The training study Generation 100 here at CERG is operating with three sessions a week with moderate or high intensity, and it is going to be exciting to see if there are differences in health outcomes in terms of length and intensity of exercise.
Maria Henningsen, CERG.