The Importance of a Life Course Perspective on Media Use

The outsized role of media use in current society is widely acknowledged, as is the need for collective, multifaceted efforts to reduce screen time and mitigate negative consequences for children’s health and wellbeing.¹  A significant body of literature reveals the known child health risks of excessive and/or inappropriate screen time, including unhealthy diet, sleep problems, excessive adiposity, poor cardiometabolic health, and increased mental health concerns.^2,3  What is less well-characterized are the long-term consequences of media use in childhood.

In this issue of Pediatrics, MacDonell and Hancox use a population-based cohort study from New Zealand with extremely high retention rates (94%, 938 of 997 surviving participants), to demonstrate that television viewing between ages 5 and 15 years was associated with metabolic syndrome, obesity, and poor fitness at age 45.⁴  Notably and disappointingly, the findings about the relationship between childhood television viewing and metabolic syndrome at 45 persist after adjusting for television viewing at age 32. Although there is broad recognition of the importance of healthy behaviors in childhood as setting up trajectories of health, there is a tendency to be hopeful that opportunities for course correction exist. Although the benefits of decreasing sedentary behaviors and media use certainly exist in adulthood, as well, these findings underscore the critical and potentially disproportionately larger influence of the childhood years on cardiometabolic health risks. If early media use is, in fact, causally related to adult metabolic syndrome, the mechanism, however elusive, has important public health consequences. Some emerging evidence reveals that the “exposome” early in childhood creates epigenetic changes that predispose to obesity. Seen in this light, limiting screen time in young children takes on even greater urgency.

Interestingly, the association between childhood television viewing and metabolic syndrome persisted after adjusting for physical activity. The authors recognize that this result is consistent with those of other studies, which reveal that the displacement of physical activities by media use in children is not the main mechanism for the negative health outcomes.⁵  In fact, in an experimental study that reduced television viewing as a mechanism to reduce BMI, physical activity did not increase although the rate of BMI increase was reduced.⁶  Although there is increasing recognition of the interrelatedness of 24-hour movement behaviors (physical activity, sedentary time, and sleep) and their importance for overall child health, there is evidence to suggest that the health consequences of each can be independent of the others. For example, a recent cross-sectional study of US adolescents revealed that a combination of high screen time and low physical activity was associated with overweight/obesity but a high step count may not offset the risk for adolescents with high screen time, and low screen time may not offset risk for those with low step count.⁷  However, a few other recent studies do provide an indication that promoting active lifestyles that adhere to healthy 24-hour movement guidelines in terms of adequate physical activity and sleep and limited screen time can be protective in terms of obesity and cardiometabolic risks even into the adult years. Garcia-Hermoso et al have reported that meeting 24-hour movement guidelines in adolescence was related to a lower risk of abdominal obesity (but not BMI) and type 2 diabetes risk 14 years later in a US cohort.^8,9  In addition, the benefits of engaging in optimal amounts of any of these 3 movement behaviors could have benefits besides weight status and cardiometabolic outcomes and extend into mental health and other domains.

So where does this leave us in terms of prioritizing how and when to intervene with regard to the ubiquitous presence of media in our lives, which is beginning earlier and earlier in childhood? We must first acknowledge that there are some limitations to this study that make the response even more challenging. There have been seismic shifts in media use over the past 40 years, including the advent of the internet, mobile phones, and social media, making it difficult to extrapolate from the sedentary experiences of the cohort participants who were growing up in the 1970s and 80s. Additionally, parent- or child-reported measures of both screen time and physical activity were problematic then, as they are problematic now. Regardless, given that children today are growing up with more screens and fewer physical activity opportunities than previous generations, the findings of this study underscore the urgency of taking a life-course perspective on media use. Obesity and metabolic syndrome are associated with an increased risk of multiple chronic diseases and early death; socioeconomic and racial/ethnic disparities have also been well-documented. Interventions are needed at individual, family, school, community, and policy levels to modify increasingly sedentary and media-infused childhoods while simultaneously studying and advancing strategies to mitigate negative health trajectories to promote population health and health equity. Changing the beginning changes the whole story.