As many as one in every three cases of Alzheimer's disease can be prevented, a new study suggests.

Alzheimer's disease is the most common type of dementia in older people. People suffering from AD have problems with memory and thinking and have lower quality of life.

Current estimates suggest that about five million Americans are living with AD. By 2050, the number of people with the condition is expected to be around 105 million people worldwide. AD is caused by a combination of genetic and environmental factors and currently, there is no cure for the disease.

A recent study by researchers at the University of Cambridge and their colleagues said that one in three AD cases is preventable.

The team said that poor physical activity, depression and low levels of education are some of the most common factors of the disease. Modifying some of these factors could lower the risk of the disease.

The study builds on earlier work that had found that one in two cases of AD can be prevented. According to researchers, previous studies have used risk factors that are related to one another. For example: diabetes, hypertension and obesity are associated with poor physical activity.

The present study found seven key risk factors that are related to Alzheimer's disease. These are:

  • Diabetes,
  • Midlife hypertension,
  • Depression,
  • Smoking,
  • Physical inactivity
  • Midlife obesity and
  • Low educational levels.

Researchers said that as many as 9 million cases of the disease can be prevented by 2050 by reducing "the relative risk from each of these risk factors by 10 percent."

"It's important that we have as accurate an estimate of the projected prevalence of Alzheimer's as possible, as well as accurate estimates of the potential impact of lifestyle changes at a societal level. Alzheimer's disease is placing an ever increasing burden on health services worldwide as well as on both patients and their carers," said Dr Deborah Barnes from the University of California, San Francisco and the San Francisco VA Medical Center, according to a news release

Leading a healthier lifestyle in old age could reduce AD risk, researchers further said.

"Although there is no single way to prevent dementia, we may be able to take steps to reduce our risk of developing dementia at older ages," Barnes added.

National Institute for Health Research Collaboration for Leadership in Applied Health Research and Care (NIHR CLAHRC) for Cambridgeshire and Peterborough funded the research and it is published in the journal The Lancet Neurology.