A provocative new analysis identifies the biggest risk factors for Alzheimer's disease -- and concludes that more than half of all cases are potentially preventable through simple lifestyle changes, such as exercising, quitting smoking and losing weight. 
 
 It offers no magic bullet against the devastating disease, which kills brain cells and leaves people mute, incontinent and unable to care for themselves. 
 
 That's because no one has yet proven that changing these factors actually will reduce risk of the disease, which affects half of all people over age 85 -- an estimated 5.2 million Americans and 75,000 people in the Bay Area alone. The cause of Alzheimer's remains unclear; like heart disease, it may be caused by a combination of factors. 
 
 But the San Francisco VA Medical Center study shows scientists where to start working. 
 
 "It's another brick in the wall suggesting that Alzheimer's doesn't have to be a passive thing that we wait to come get us. There are life modifiers that may reduce our risk," said William H. Fisher of the Alzheimer's Association. 
 
 Costly disease 
 
 It is an issue that has taken on increased urgency with the aging of baby boomers. An estimated 5.3 million people in the United States are diagnosed with the disease, and the number is expected to triple by 2050. Because caregiving is so expensive, experts predict the cost to Medicare and Medicaid will jump from $170 billion in 2009 to $800 billion in 2050 -- more than the military budget. 
 
 The conclusions based on a statistical analysis of published data, were presented Tuesday at the Alzheimer's Association International Conference in Paris and was published in the journal Lancet Neurology. 
 
 "It suggests these modifiable risk factors might make a huge difference in those projections," said VA researcher Deborah Barnes in a phone interview from France. "The next step is to do the clinical trials that ask, 'If we change a risk factor, will it reduce rates of dementia?' — 
 
 There are many reasons to follow practices to improve general health -- such as a good diet, exercising and keeping mentally engaged, Fisher noted. 
 
 Even if these steps don't guarantee protection against the degenerative brain disease, it might delay its onset. 
 
 But Fisher cautioned: "A lot of people are going to do everything right, and they'll still get Alzheimer's disease. We have to be careful not to blame the victim." 
 
 The study found that the biggest changeable factor in the United States is physical inactivity -- accounting for 21 percent of the risk, followed by depression and smoking. When added together, these risk factors account for about 50 percent of the cases. 
 
 Even a 10 percent reduction in the seven risk factors, which also include diabetes, depression, midlife high blood pressure and low education, could prevent 184,000 Alzheimer's cases in the United States, and 1.1 million cases worldwide, could be prevented, according to the study. 
 
 The findings were based on complex mathematical analysis, not a new study of patients. They assumed a causal relationship between each risk factor and dementia. "What we need to do now is figure out whether that assumption is correct," said Barnes. 
 
 The best way to truly prove prevention is to run a controlled experiment that randomly assigns similar people to different lifestyle factors, like diet, then watch, asking: Do they get Alzheimer's, or not? But this takes money -- and time. 
 
 Just two decades ago, many people thought dementia was a normal part of aging, so not much attention was paid. 
 
 But in December, Congress voted unanimously to create a national plan to combat Alzheimer's disease with the same energy as the attacks on cancer and AIDS. The national plan will reinforce efforts to detect brain changes that occur years before people develop symptoms. 
 
 Last year, in disappointing news, a panel assembled by the National Institutes of Health surveyed the scientific literature, and found no research good enough to prove that Alzheimer's can be fended off. 
 
 Early adopter 
 
 But Molly Vanden, of Walnut Creek, already is taking prevention seriously, rather than waiting for a definitive link. She is only 27, but her father, Marc, was diagnosed at 54. He is now 61, and in the middle stages of the disease. 
 
 She walks around her neighborhood three times a week, and on weekends goes for longer five-mile hikes in Martinez with her mother and her dog. 
 
 "Anything I can do will help," she said. "I recognize that scientists don't say it's a cure. But I'm hoping it will help. There are things I can do for a healthy lifestyle." 
 
 Duke University's Dr. James Burke, a member of the group that conducted the landmark NIH study, said the new analysis "attempts to answer an interesting and important question. What would happen to the prevalence of Alzheimer's disease if we reduced the occurrence of risk factors that may cause Alzheimer's disease?" 
 
 So far, there is little evidence that these risk factors actually cause Alzheimer's disease, said Burke, who directs Duke's Memory Disorders Clinic. There are many examples in medicine where things that seemed linked weren't, he said. 
 
 But the magnitude of the problem makes it important to take steps now, rather than waiting for a definitive answer. 
 
 "Reducing smoking, obesity and increasing exercise will have huge benefits in quality of life independent of whether it reduces the number of people with dementia," he added. 
 
 Contact Lisa Krieger at 408-920-5565. 

 Half of Alzheimer’s cases worldwide can be traced to seven common risk factors, a new study shows. 
 
 The findings also suggest that by tackling those underlying issues – which range from lack of education to obesity – the rising tide of dementia could be slowed considerably. 
 
 “We are assuming that when you change the risk factor, then you change the risk,” said Deborah Barnes , an associate professor of psychiatry at the University of California, San Francisco, and lead author of the study. “What we need to do now is figure out whether that assumption is correct.” 
 
 More related to this story 
 
 
 
 Worldwide, an estimated 33.6 million people are living with Alzheimer’s and related dementias, including more than 500,000 in Canada. There are more than six million new cases diagnosed each year, including 110,000 in Canada. 
 
 The research, published online Tuesday in the medical journal Lancet Neurology , is a systematic review of earlier studies examining risk factors for Alzheimer’s disease. 
 
 Dr. Barnes and her colleagues used mathematical modelling to estimate the global impact of the modifiable risk factors. They calculated that 17.2 million of the current cases may have been prevented. 
 
 The seven risk factors, in descending order of magnitude, were identified as: 
 
 * Low education: “Use it or lose it” is an important credo in Alzheimer’s prevention. Schooling is key because stimulating the brain builds neural networks and the more education a person has the more likely they are to engage in stimulating brain activity. Yet, worldwide, 40 per cent of the population has a primary school education or less. The researchers estimated that low education was associated with 19.1 per cent of Alzheimer’s cases, or 6.4 million cases globally. 
 
 * Smoking: Among other things, smoking weakens blood vessels and it affects blood flow to the brain. But almost one-third of adults in the world still smoke. The research estimates 13.9 per cent of Alzheimer’s cases are linked to smoking. 
 
 * Physical inactivity: Studies show that people who are physically active have better cognitive abilities and are less likely to develop dementia. Worldwide about one in six people are inactive. The new study found that 12.7 per cent of Alzheimer’s cases were likely due to inactivity. 
 
 * Depression: People who suffer from depression have more than double the risk of developing dementia. About one in seven people in the world will suffer from serious depression. Researchers calculated that about 10.6 per cent of Alzheimer’s cases could be traced to depression. 
 
 * High blood pressure: About one in nine people in the world have hypertension in middle age. The study estimated that poorly-controlled blood pressure accounts for 5.1 per cent of Alzheimer’s cases. 
 
 * Diabetes: Research shows patients with type 2 diabetes have a significantly higher risk of developing Alzheimer’s. Globally, almost seven per cent of adults have diabetes. The research team found it could be responsible for about 2.4 per cent of Alzheimer’s cases. 
 
 *Obesity: Women and men who are obese at middle age have an increased risk of dementia later in life. Worldwide about 3.5 per cent of the population is both obese and middle-aged. The study found that obesity is associated with about two per cent of Alzheimer’s cases. 
 
 The findings were also presented Tuesday at the Alzheimer’s Association International Conference in Paris . 
 
 Dr. Barnes said if these risk factors were eliminated entirely it is not realistic to think these risk factors could be eliminated entirely, but even small reductions could have a significant impact. 
 
 The researcher estimated that reducing the seven key risk factors by 10 per cent would translate to 1.1 million fewer cases of Alzheimer’s, while a 25 per cent reduction would translate into 3 million fewer cases a year. 
 
 “It gives us a little bit of hope about things we could do now about the epidemic that is coming our way,” Dr. Barnes said. She said that is particularly true given the lack of progress in developing effective treatments for Alzheimer’s and other forms of dementia. 
 
 Currently, the number of people living with dementia is doubling every 20 years and, without significant advances in prevention, the number is expected to reach 115 million in 2050.
– At least half of all cases of Alzheimer's disease are linked to common risk factors, and researchers believe the number of cases could be sharply reduced if people took steps to tackle those underlying issues. To reduce the risk, researchers say people need to stay active both mentally and physically, quit smoking, and improve their diets, the Globe and Mail reports. The biggest risk factor is having a low level of education, which researchers say is linked to almost a fifth of cases worldwide. "We are assuming that when you change the risk factor, then you change the risk,” the lead researcher noted. "What we need to do now is figure out whether that assumption is correct." The president of the Alzheimer's Association hailed the research as "another brick in the wall suggesting that Alzheimer's doesn't have to be a passive thing that we wait to come get us"—but he stressed that many of the causes are still unknown. "A lot of people are going to do everything right, and they'll still get Alzheimer's disease. We have to be careful not to blame the victim," he told the San Jose Mercury-News.