An increase in sedentary time since childhood caused a progressive enlargement of the heart, a new study shows. However, light physical activity may reduce the risk. The study was carried out in collaboration between the Universities of Bristol and Exeter and the University of Eastern Finland, and the results were published in the prestigious European Journal of Preventive Cardiology .
Left ventricular hypertrophy refers to an excessive increase in the mass and size of the heart. In adults, it is known to increase the risk of heart attacks, strokes, and premature death.
In the present study, 1,682 children selected from the University of Bristol’s Kids of the 90s cohort were followed from ages 11 to 24 years. At baseline, they spent an average of six hours per day in sedentary activities, which increased to nine hours per day in adulthood. This increase in sedentary time was associated with a progressive enlargement of the heart, contributing 40% of the total increase in cardiac mass within a seven-year growth period from adolescence to adulthood.
In contrast, an average of three to four hours per day of light physical activity (LPA) throughout follow-up reduced the increase in cardiac mass by 49%. Higher LPA was also associated with better cardiac function.
Participation in moderate to vigorous physical activity (MVPA) showed signs of a slight increase in heart size, by 5%, which is largely physiological.
Previous studies in the same population have linked excessive sedentary lifestyle with increased inflammation , high insulin levels, fatty obesity, dyslipidemia, and arterial stiffness . Light physical activity ( LPA) has emerged as an effective approach to reduce the harmful effects of childhood sedentary lifestyle. However, no study in the world has previously examined whether long-term exposure to LPA since childhood has the potential to reverse the increase in cardiac mass. This is because repeated echocardiographic evaluations of the heart in a large population of healthy young people are rare.
The current study is the largest and longest study tracking movement behavior measured with accelerometer and repeated echocardiography in the world. Participants wore waist-worn accelerometers at ages 11, 15, and 24 years for 4 to 7 days and had echocardiographic measurements of heart structure and function at ages 17 and 24 years. Their fasting blood samples were also repeatedly measured for low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, glucose, insulin, and high-sensitivity C-reactive protein. Blood pressure, heart rate, smoking, socioeconomic status, family history of cardiovascular disease, as well as fat mass and lean mass measured by dual-energy X-ray absorptiometry were taken into account in the analyses.
“There is growing evidence that childhood sedentary lifestyles are a health threat that must be taken seriously. There must be a paradigm shift in the way we view childhood sedentary behavior, as growing evidence points to a ticking time bomb,” says Andrew Agbaje, award-winning physician and associate professor (lecturer) of clinical epidemiology and child health at the University from eastern Finland.
“ Light physical activity (LPA) is an effective antidote to a sedentary lifestyle. It’s easy to accumulate three to four hours of LPA a day. Examples of LPA are outdoor games, playing on the playground, walking the dog, running errands for parents, walking and biking to the mall or school, taking a walk in the park, playing in the woods, gardening, casual basketball, soccer, floorball, golf, frisbee, etc. We can encourage children and adolescents to engage in LPA daily for better cardiovascular health,” says Agbaje.
Final synthesis
The objective of this longitudinal study that included 1682 children and adolescents was to examine the effect of sedentary time (ST), light intensity physical activity (LPA), moderate to vigorous intensity physical activity (MVPA) on changes in Cardiac structure and functional properties during growth to early adulthood.
Sedentary time ( ST) accumulated since childhood contributed a maximum of 40% during growth from adolescence to adulthood. Cumulative light-intensity physical activity ( LPA) since childhood was associated with a decrease in cardiac mass, equivalent to an average reduction of −49% (−1.49 g/m2.7 from 3 g/m2, 7) in the increase in cardiac mass during the 7-year observation period.
Each minute of cumulative moderate-to-vigorous intensity physical activity (MVPA) since childhood was associated with a 5% progressive increase in cardiac mass, equivalent to +0.15 g/m2.7 of a 3 g increase /m2.7 during growth from adolescence to young adulthood.
Participation in LPA of at least 3 h/day and decreased sedentary time were longitudinally associated with healthier cardiac indices in the young population. The contribution of ST to the increase in cardiac mass is eight times greater than the physiological increase associated with moderate to vigorous intensity physical activity (MVPA).
Therefore, progressively increasing childhood sedentary lifestyle may independently and pathologically contribute to the worsening of cardiac structural and functional alterations in the young population. Childhood sedentary lifestyle causes increased body fat, inflammation, blood pressure, lipid levels, arterial stiffness, and subsequently cardiac enlargement, thus increasing the risk of adverse cardiovascular health consequences in old age.
Dr. Agbaje’s research group (urFIT-child) is supported by research grants from the Jenny and Antti Wihuri Foundation, the Central Fund of the Finnish Cultural Foundation, the Regional Fund of the Finnish Cultural Foundation Savo Norte, the Orion Research Foundation, Aarne Koskelo Foundation, Antti and Tyyne Soininen Foundation, Paulo Foundation, Yrjö Jahnsson Foundation, Paavo Nurmi Foundation, Finnish Foundation for Cardiovascular Research, Ida Montin Foundation, Eino Räsänen Fund, Matti and Vappu Maukonen Fund, Foundation for the Pediatric Research and Alfred Kordelin Foundation.
