It is estimated that nearly 7 million Americans 65 years and older are living with Alzheimer's Disease. There may be a way to help lower these numbers, a recent study finds, by doing more aerobic exercise. How? The key is making sure we get enough aerobic exercise in our middle years and beyond, can reduce the risk of developing dementia — including Alzheimer's disease.

It's all about maintaining cardiorespiratory fitness (CRF). You develop cardiorespiratory fitness by doing regular aerobic exercise — a workout that boosts oxygen uptake in our lungs and heart. It is what helps us to sustain high-intensity activities over an extended period without experiencing exhaustion.

By boosting brain health, being physically fit lowers the risk of dementia and delays someone developing it by almost 18 months.

“Our study underscores the critical role of cardiovascular fitness in reducing dementia risk, even for those genetically predisposed to Alzheimer's disease,” lead author, Weili Xu, a professor in the Aging Research Center at Karolinska Institute in Stockholm, Sweden, said in a press release.

The Swedish research team analyzed the health data of over 61,000 people between the ages of 39 and 70 when they enrolled in the UK biobank study between 2009 and 2010. The UK Biobank is an on-going health research project that collects detailed genetic, lifestyle and health information from half a million people in the United Kingdom.

At the time of this study, none of the participants had dementia. They were followed for up to 12 years to see how their health developed.

The participants' cardiorespiratory fitness was assessed through a six-minute exercise test sitting on a stationary bike when they first joined the Biobank. Their cognitive function was measured by neuropsychological tests, and their genetic likelihood of developing dementia was determined via a polygenic test that uses a person's DNA to look at the likelihood of developing Alzheimer's disease, heart conditions, diabetes and several common cancers.

After analyzing the Biobank data, the Swedish researchers concluded:

  • By boosting brain health, being physically fit lowers the risk of dementia and delays someone developing it by almost 18 months.
  • Regular cardiovascular exercise not only maintains cognitive function, it can even help people who are genetically more predisposed to dementia and reduce their risk by up to 35 percent.

Good cardiovascular fitness doesn't happen without an effort. It naturally declines as we age at a rate of 3 to 6 percent during a person's 20's and 30's, according to the American Heart Association. It continues to decline at a rate of more than 20 percent per decade in your 70's and beyond.

You can increase your cardiorespiratory fitness and gain its cognitive and physical benefits. Begin with exertion that gets your heart and lungs working for just 10 to 15 minutes at a time and then gradually build it up. The AHA recommends that adults get at least 150 minutes (2 1/2 hours) of moderate to vigorous activity per week. Thirty minutes a day five days a week is an easy goal to remember. Some people will be able to do more. It's important to set realistic goals based on your own health and abilities.

Good cardiovascular fitness doesn't happen without effort. It also declines as we age — at a rate of 3 to 6 percent during a person's 20's and 30's and at more than 20 percent per decade in your 70's and beyond.

Examples of the kind of exercise that will help your heart and mind include:

  • Walking briskly
  • Running or jogging
  • Dancing
  • Biking
  • Climbing stairs at work or at home

Be sure to check with your healthcare provider before starting any new exercise routine.

The study is published in the British Journal of Sports Medicine.