Going to the doctor, paying bills, taking a driving test—older adults should try to tackle their most taxing tasks earlier in the day, claims new evidence from the University of Toronto (UT) that suggests aging brains function best in the morning hours.

The findings align with previous conclusions that people of all ages experience fluctuations in energy and attention levels throughout the day, with noticeable dips in brainpower occurring in the afternoon or following a meal. But the effects of afternoon brain fog may impact older adults more severely, according to John Anderson, a Ph.D. candidate at UT and lead author of the recent study. "This age group is more focused and better able to ignore distraction in the morning than in the afternoon," he says.

Anderson and his team developed a computer-based memory test and sprinkled elements of distraction (randomly flashing words and pictures) throughout. They administered the test to a group of younger adults (19-30 years old) and a group of older adults (60-82 years old) at different times of the day. During each test, participants' brain activity was monitored using an fMRI scan that enabled researchers to determine which areas of the brain were being used the most.

When tested in the morning, both the younger and the older groups performed relatively well on the exam and were able to disregard the irrelevant information that popped up on the screen. However, when the older adults were tested between the hours of 1:00 p.m. and 5:00 p.m., they were 10 percent more likely to get derailed by the distractions. During this time, the older adults' brain activity also suggested they were slipping into a state of mental autopilot similar to the one that occurs when a person "zones out."

The study offers insight into how older adults should schedule their daily tasks for optimum efficiency: harder, more complex actions should be reserved for the early morning hours, while simpler errands that require less brain power are better off left until the afternoon.

Lynn Hasher, Ph.D., a professor of psychology at UT and senior author of the paper, points out that the findings also shed light on how time of day could affect a person's performance on dementia screening tests. "Since older adults tend to be morning-type people, ignoring time of day when testing them on some tasks may create an inaccurate picture of age differences in brain function," she says.

As routine dementia exams are increasingly incorporated into the medical care of aging adults, it's important for patients, caregivers and doctors alike to keep in mind the potential effect of the time of day on a person's performance on these tests.

Learn more about dementia screening tests and why some physicians are wary of using them too often: Why Experts Don't Want All Seniors to Get Screened for Dementia