A Florida-based researcher of Indian origin has found that heavy drinkers and heavy smokers are more likely to develop Alzheimer's disease early than those who do not drink or smoke heavily.
"These results are significant because it's possible that if we can reduce or eliminate heavy smoking and drinking, we could substantially delay the onset of Alzheimer's disease for people and reduce the number of people who have Alzheimer's at any point in time," says Dr. Ranjan Duara of the Wien Center for Alzheimer's Disease at Mount Sinai Medical Center in Miami Beach.
"It has been projected that a delay in the onset of the disease by five years would lead to a nearly 50-percent reduction in the total number of Alzheimer's cases. In this study, we found that the combination of heavy drinking and heavy smoking reduced the age of onset of Alzheimer's disease by six to seven years, making these two factors among the most important preventable risk factors for Alzheimer's disease," said Duara.
During the study, the researchers looked at 938 people aged 60 and above, who were diagnosed with possible or probable Alzheimer's disease.
Collecting information on the subjects' drinking and smoking history from their family members, the researchers determined whether the participants had the a4 gene variant of the APOE gene, which increases the risk of Alzheimer's disease.
The researchers focussed on this variant because people having it also develop Alzheimer's at an earlier age than those who do not have the gene variant.
Seven per cent of the participants had a history of heavy drinking, which was defined as more than two drinks per day.
Twenty per cent had a history of heavy smoking, which was defined as smoking one pack of cigarettes or more per day. Twenty seven per cent had the APOE a4 variant.
Based on their analysis, the researchers came to the conclusion that people who were heavy drinkers developed Alzheimer's 4.8 years earlier than those who were not heavy drinkers.
They also observed that heavy smokers developed the disease 2.3 years sooner than people who were not heavy smokers, and that people with APOE a4 developed the disease three years sooner than those without the gene variant.
The researchers said that people with all three risk factors developed the disease 8.5 years earlier than those with none of the risk factors.
They reveal that 17 people in the study, who had all three risk factors, developed Alzheimer's at an average age of 68.5 years.
On the other hand, 374 people without the three risk factors developed the disease at an average age of 77 years.
The study will be presented at the American Academy of Neurology 60th Anniversary Annual Meeting in Chicago.