According to the World Health Organisation, there are more than 35 million people worldwide suffering from Alzheimer disease (that is, about two thirds of all people with dementia) and the number of people affected could exceed 50 million in 2030, given the aging of the population worldwide, with life expectancy currently over 70 years.
However, importantly, it is also true that even though the prevalence (total number of cases) of this terrible disease is increasing – due to the aging of the population – the incidence (the proportion of cases in each age group) has clearly decreased in high-income countries. This development is surprising but has been confirmed by several rigorous studies. There are several reasons behind it: better management of cardiovascular risk factors and in particular hypertension. We know that indeed, blood pressure figures between the ages of 40 and 60 have an effect on the functioning of the brain after the age of 80. Elderly patients who have dementia today were in their 40s and 50s in the 1960s, a time when no antihypertensive treatments were available.
Hypertension affects the arteries in the brain, which can have two main consequences:
The risk of stroke is well-known, but the effects on memory are less well-known. Recent studies have shown the impact of blood vessel (vascular) abnormalities on the memory, creating a risk of “vascular dementia” or Alzheimer disease. A combination of different factors increases the risk of memory problems and Alzheimer disease.
The presence of vascular risk factors (hypertension, diabetes, raised cholesterol levels) progressively damages the walls of the arteries in the brain. These vascular changes cause poor blood supply to the brain and can cause damage to very small areas (only a few millimetres wide) of the brain (lacunes), which when multiplied can eventually cause symptoms of dementia.
In total, almost half of cases of Alzheimer disease in the world (17 million) are thus potentially due to risk factors upon which we can act.
So we now know that we can take very effective steps, using various means, to prevent dementias, which still have no effective treatment and whose causes have not been clearly identified. Recent research has shown that reducing blood pressure with an antihypertensive treatment can reduce the risk of dementia by 50%, which is why hypertension must be treated, ensuring that blood pressure stays within normal limits (140/90 mm Hg in the doctor’s office).
Internal Medecine Service