An estimated 2 million people in the United States suffer from severe dementia, and 5 to 8 percent of people over the age of 65 have some form of dementia. Globally, the number of people living with dementia is expected to increase from 50 million in 2017 to 152 million by 2050, a 204 percent increase.

This increase in the prevalence of dementia may be related to a greater awareness and more accurate diagnosis or to increased longevity that has created a larger elderly population, the age group most commonly affected.

Dementia is a disease of concern because the decline in memory and other cognitive functions that characterize this condition also leads to a loss of independent function that has a wide-ranging impact on individuals, families and healthcare systems. Now, a new study examines the role of fitness in the onset of symptoms.

Alzheimer's disease (AD) is the most common type of dementia and accounts for an estimated 60 to 80 percent of cases. The hallmark pathologies of Alzheimer's are the progressive accumulation of the protein fragment beta-amyloid or plaques outside neurons in the brain and twisted strands of the protein tau or tangles inside neurons. These changes are eventually accompanied by the damage and death of neurons.

When patients present with symptoms of dementia, physicians must conduct tests to identify the underlying brain disease or other condition(s) causing symptoms. However, AD is complex, and few, if any, drugs or interventions result in successful treatment.

Current approaches focus on helping people maintain mental function, manage behavioral symptoms and slow down certain problems, such as memory loss. While some researchers hope to develop therapies targeting specific genetic, molecular and cellular mechanisms so that the actual underlying cause of the disease can be stopped or prevented, other researchers have evidence that exercise improves brain health and could be key in preventing Alzheimer's.

According to Dr. Kan Ding, a neurologist from the Peter O'Donnell Jr. Brain Institute who authored a recent study, improving people's fitness may also improve their brain health and slow down the aging process. The study suggests that the lower the fitness level, the faster the deterioration of vital nerve fibers in the brain that result in cognitive decline, including memory issues characteristic of dementia.

The research included six medical centers across the country and more than 600 older adults at high risk to develop AD who had early signs of memory loss or mild cognitive impairment. It focused on whether performing regular aerobic exercise and taking specific medications to reduce high blood pressure and cholesterol levels can help preserve brain function.

Patients were given memory and other cognitive tests to measure brain function. The scientists measured cardiorespiratory fitness with maximal oxygen uptake and brain imaging to measure the functionality of each patient's white matter. The researchers determined that lower fitness levels were associated with weaker white matter, which in turn correlated with lower brain function.

To better understand and treat dementia, other teams at the O’Donnell Brain Institute are designing tests for the early detection of patients who will develop dementia and seeking methods to slow or stop the spread of toxic proteins associated with the disease, such as beta-amyloid and tau, which are implicated in destroying certain groups of brain neurons.

If it is true that what is bad for our hearts is bad for our brains, then more studies like this one are needed to determine how the two are intertwined to help address dementia.