Smart kids, sedentary adults?

In a cohort of Finnish 25-year-olds, those who had higher cognitive ability in early childhood were more inactive physically in young adulthood, as shown in a study by Kumpulainen et al., published in Health Psychology.

Physical inactivity means both low levels of moderate-to-vigorous physical activity (such as brisk walking and running), and high levels of sedentary behaviours (such as reading, TV viewing and computer use, while sitting or laying down). Both of these factors independently predict adverse health-related outcomes. One proposed factor underlying individual differences in health related behaviours, including physical activity, is early life cognitive ability. In our study, we examined whether cognitive ability in childhood predicts physical activity and inactivity in young adulthood.

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The study sample comprised 500 participants of the Arvo Ylppö Longitudinal Study (AYLS). In childhood, at an average of 4.5 years, the participants underwent neurocognitive testing. In adulthood, at the mean age of 25 years, they wore a wrist-worn accelerometer for a week, to provide data on physical activity. They also self-reported their level of physical activity during occupational and leisure-time.

Results showed that in young adulthood, higher cognitive ability in childhood was associated with more sedentary time and less time spent in light physical activity such as slow walking. It was also associated with lower intensity of daily physical activity, and decreased odds of having a physically demanding job in young adulthood.

It may seem surprising that those children with high cognitive ability were physically less active in adulthood: in many cases, high cognitive ability is associated with positive health-related behaviours. In our study, however, the associations seemed (partly) explained by differences in the educational level that the participants had attained or were pursuing. This would suggest that lower physical activity and more time spent in sedentary behaviours may reflect the lower strenuousness of daily activities in those with a higher educational level.

Physical activity patterns are moderately stable across adulthood and physical inactivity tends to increase with age. Increasing awareness of the benefits of physical activity-related health promotion should be targeted at young adults whose daily activities include a lot of sedentary behaviours.