People are living longer, and while that is a good thing, growing older in today's world presents challenges.

In a 2009 Pew Research Center survey, about 1 in 4 adults ages 65 and older reported experiencing memory loss. About 1 in 5 said they had a serious illness, were not sexually active, or often felt sad or depressed.

Roughly 1 in 6 reported they were lonely or had trouble paying bills. Also, 1 in 7 could not drive, and 1 in 10 felt they weren't needed or were a burden to others.

It has been established that the effects of aging on the brain and cognition are widespread and have multiple etiologies. Aging has its effects on the molecules, cells, vasculature, gross morphology and cognition.

As we age our brains shrink in volume particularly in the frontal cortex. As our vasculature ages and our blood pressure rises, the possibility of stroke and ischemia increases, and our white matter develops lesions.

Memory decline also occurs with aging, and brain activation becomes more bilateral for memory tasks. Protective factors that reduce cardiovascular risk namely regular exercise, a healthy diet, and low to moderate alcohol intake have been suggested to aid the aging brain.

Interestingly, a new study in NeuroImage shows that age-related differences in brain health, specifically the strength of connections between different regions of the brain, vary with fitness level in older adults. The findings suggest that greater cardiorespiratory fitness — a measure of aerobic endurance — relates to stronger brain connections and likely improves long-term brain function in aging populations.

The study was led by Michelle Voss while a postdoctoral researcher at the University of Illinois with Beckman Institute director Arthur Kramer and kinesiology and community health professor Edward McAuley. The results provide the strongest evidence to date that fitness in an older adult population can have substantial benefits to brain health in terms of the functional connections of different regions of the brain.

One popular technique of measuring brain health across the lifespan involves measuring the strength of connections between different parts of the brain while the person is completing a task or during wakeful rest. The latter is known as resting-state functional connectivity. Research has shown that some of these connections weaken with increasing age, indicating deteriorating brain health.

Using functional magnetic resonance imaging, Voss and colleagues measured the strength of these connections throughout the brain in younger and older adults atrest, and the team confirmed that most connections were weaker for older adults when compared with younger adults.

Next, the researchers examined the role of cardiorespiratory fitness on resting-brain connectivity in older adults. Fitness is determined by how efficiently someone uses oxygen during physical activity such as running on a treadmill. However, other factors besides habitual physical activity may alter how fitness affects brain health, such as individual genetic makeup.

The researchers found a relationship between fitness and the strength of the connections between certain brain regions in older adults at rest that was independent of their level of physical activity, suggesting the benefits of fitness seem to occur within the low-to-moderate range of endurance and the benefits of fitness for the brain may not depend on being extremely fit.

The study concludes that there is a positive role of cardiorespiratory fitness, beyond habitual physical activity, on brain health as people age. It's an intriguing concept because it suggests there could be clues in how the body adapts from regular activity for some people more than others.

According to Voss, this will help understanding how fitness protects against age-related cognitive decline and dementia.