The study showed that having the harmful form of TOMM40 drastically increases one's susceptibility when other risk factors - such as having a gene called ApoE-4 - are present.
People who have ApoE-4 are three to eight times more likely to develop Alzheimer's.
"The TOMM40 gene influences the ease with which molecules can get in and out of mitochondria, the energy production centre and stress mediator of cells," said Dr. Steven Potkin, lead author of the study and UCI psychiatry and human behavior professor.
"TOMM40 also processes materials that form amyloid plaque, a hallmark of Alzheimer's.
"With aging, the number and function of mitochondria decrease, accompanied by a parallel increased risk of developing Alzheimer's. This study points to the use of mitochondrial-based therapies for treating the disease," he added.
Duke University scientists have also found that patients with TOMM40 developed Alzheimer's an average of seven years earlier than those without the gene.
The study is published in the journal PLoS One.