Middle aged people who smoke, have hypertension or diabetes are more likely to develop dementia in later life, says a study published online by the Journal of Neurology, Neurosurgery and Psychiatry.
People who smoke are 70% more likely than those who have never smoked to develop dementia, the US research found, while people with high blood pressure were 60% more likely to develop dementia than those without hypertension.
Dementia is a growing public health problem affecting older people in developed countries and there are an estimated 700,000 people with dementia in the UK. It has been predicted the number will rise to more than one million by 2025 and 1.7million by 2051.
Previous studies have shown that the presence of cardiovascular risk factors including high blood pressure, diabetes, obesity and smoking increase the risk of developing subsequent dementia, but have often failed to show the relationship.
Researchers from the universities of Minnesota, North Carolina and John Hopkins and the University of Mississippi Medical Center studied more than 11,000 people aged 46-70 who were participants in the Atherosclerosis Risk in Communities (ARIC) study in 1990-92.
People underwent a physical examination and cognitive testing at that time and were followed up until 2004 to see how many were hospitalised with dementia.
After following their progress, the researchers identified 203 cases of hospitalisation with dementia. Smoking, high blood pressure and diabetes were all strongly associated with dementia in white participants and African-Americans.
They also found that people with diabetes were more than twice as likely than those without diabetes to develop dementia, but no association was found between people who were obese/overweight and dementia in later life.
The results showed that rates of hospitalisation with dementia increased exponentially with age in men and women and in different ethnic backgrounds.
Overall, African-Americans had a two and a half times higher rate of hospitalisation than white people and African-American women in particular had the highest rates of all.
The researchers said people should consider modifying their lifestyle in mid-life to avoid developing dementia.
Smoking cessation and prevention or control of high blood pressure and diabetes starting in midlife may have the added benefit of decreasing dementia hospitalisation risk.
Neil Hunt, chief executive of the Alzheimer’s Society, said: “Dementia is one of people's biggest fears in later life, but very few people realise that there are things they can do to reduce their risk of developing this devastating condition.
“This study adds weight to the growing evidence that a healthy heart means a healthy brain. Evidence suggests that the best way to reduce your risk of developing dementia is to keep active, eat a balanced diet, don't smoke and to get your blood pressure and cholesterol checked regularly.”