In March 1946, less than a year after the end of World War II, the Medical Research Council of the UK commenced a longitudinal study to follow the health and development of 5,362 babies, all born in the same week in England, Wales and Scotland. Today, this is the longest running major birth cohort study in the world, and the surviving participants are soon to turn 77 years old. There have been at least 24 follow-up contacts with all surviving members of the cohort, with the latest full testing conducted when they were aged 69.
Previous research using data from this 1946 British birth cohort has demonstrated the beneficial effects of being physically during the midlife period on verbal memory. Following on from this, researchers from the MRC Unit for Lifelong Health and Ageing at University College London have now investigated whether the timing of physical activity has an influence on improved cognitive function in later life.
The participants reported their levels of physical activity at follow-up surveys conducted at the ages of 36, 43, 53, 60–64 and 69, by which time only 1,417 of the original participants were available. At each age they completed a questionnaire to assess how often they had taken part in any sports, vigorous leisure activities or exercise in the previous month.
Their responses were categorized into: not active (no participation in physical activity/month); moderately active (participated 1–4 times/month); most active (participated 5 or more times/month), and then summed across all 5 assessments to create a total score ranging from 0 (inactive at all ages) to 5 (active at all ages).
The researchers assessed cognitive function at age 69 using the validated ACE-111, which tests attention and orientation, verbal fluency, memory, language, and visuospatial function. They also used tests of verbal memory (word learning test) and processing speed (visual search speed), and analyzed the associations between cognitive function and levels of physical activity.
The researchers were particularly keen to know if physical activity is most beneficial to later-life cognitive function when undertaken in specific ‘sensitive’ periods across the life course, or when undertaken across multiple time periods.
Their results, published in the Journal of Neurology, Neurosurgery & Psychiatry, show compelling evidence of the positive effects of being, and remaining, physically active across 30 years of adulthood on later-life cognition. Essentially, they find that any regular leisure time physical activity, carried out at any age during adulthood, is significantly associated with better brain function in later life. However, maintaining an exercise routine throughout adulthood seems to be best for preserving mental acuity and memory.
The researchers found that 11 percent of participants were physically inactive at all five survey times. Around 17 percent of participants were active at only one of the survey times, whereas 20 percent were active at two and three of them; 17 percent were active at four of the survey times, and 15 percent were active at all five. Those people who reported being physically active at all five of the survey times were more likely to have higher cognitive performance, better verbal memory and faster processing speed at the age of 69.
The effect sizes were similar across all adult ages, and for those who were moderately and most physically active, “suggesting that being physically active at any time in adulthood, even if participating as little as once per month, is linked to higher cognition,” wrote the researchers.
The positive association between cumulative physical activity and later life cognitive performance was partly explained by childhood cognition, socioeconomic position, and education. However, the effect remained significant even when these variables were accounted for in the statistical analysis.
“Together, these results suggest that the initiation and maintenance of physical activity across adulthood may be more important than the timing … or the frequency of physical activity at a specific period,” explained the researchers.
The study has some limitations, including the fact that it is an observational investigation and so cannot attribute cause to the differences identified in cognitive function. In addition, all the participants were White and there was a disproportionately high attrition rate among socially disadvantaged participants. No data were collected from participants about the intensity or duration of physical exercise that they undertook, nor about whether they actually adhered to the regimen they selected during the surveys.
But the researchers nevertheless conclude: “Our findings support guidelines to recommend participation in any physical activity across adulthood and provide evidence that encouraging inactive adults to be more active at any time, and encouraging already active adults to maintain activity, could confer benefits on later life cognition.”
By Alison Bosman, Earth.com Staff Writer
Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.