Individuals who have systolic hypertension and high levels of blood cholesterol in midlife appear to have a significantly increased risk of developing Alzheimer's disease in later life, report Finnish researchers.
A team from the University of Kuopio collected data from 1449 men and women over an average period of 21 years. These subjects were 65-79 years of age in 1998, when they were reexamined, and had been previously examined when they were 40-64 years of age.
The researchers concluded that, in midlife, those with a systolic blood pressure of 160 mmHg or more, or a blood cholesterol concentration of 6.5 mmol/L or more, had more than twice the risk of developing Alzheimer's than those with normal systolic blood pressure and blood cholesterol.
Subjects who had both risk factors in midlife had a risk of developing Alzheimer's disease that was 3.5 times greater than in those with only one of the risk factors alone.
The team also found that a high diastolic blood pressure in midlife had no effect on Alzheimer's risk.
Previous studies have shown evidence of an association between Alzheimer's disease and midlife cardiovascular factors in single sex groups, but this, say the researchers, is the first population based study to investigate the connection in both sexes (BMJ, 2001; 322: 1447-51).
In a related study, scientists at Stanford University School of Medicine, in California, suggest there may be a link between sleep disordered breathing (SDB) and an increased risk of developing Alzheimer's. The reason for this, say the researchers, is the presence of the e4 allelic variant of apolipoprotein E (apoE), a protein involved in fat metabolism.
Data were collected from participants as part of an ongoing population study of sleep disorders in middle aged adults that began in 1989. After adjusting for factors such as age, sex, body mass index and ethnic group, subjects with apoE e4 had a significantly higher probability of moderate to severe SDB than those without the e4 allele 12 per cent versus 7 per cent.
Since the e4 variant predisposes individuals to cardiovascular problems as well as Alzheimer's disease, the researchers hint that all three conditions may be connected in a way we simply don't yet fully understand (J Am Med Assoc, 2001; 285: 2888-90).
Finnish researchers have also confirmed the connection between e4 in the very elderly and an increased risk of Alzheimer's. Of those who had the e4 allele, 71 per cent developed Alzheimer's versus only 22 per cent of those who did not (Neurology, 2001; 56: 1690- 6).