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Screen time ≥2 hours/day at 8 years of age was associated with an increased risk of developing IBD.
Screen time during childhood may be associated with an increased risk for later development of inflammatory bowel disease (IBD), according to findings from a prospective birth cohort study.
High screen time at 8 years of age was associated with a greater risk of developing IBD, while measures of screen time at 3 years of age and physical activity at 8 and 3 years of age were not related to subsequent risk of IBD.1
“Ecological evidence has linked the rising incidence of IBD to multiple environmental factors, including an increasingly sedentary lifestyle,” wrote investigators.1 “To our knowledge, there has been no previous prospective examination of the degree of physical activity and screen time in childhood with the risk of later IBD.”
As many as 1.6 million people in the US are affected by IBD, with most diagnosed before age 35. The exact cause of the autoimmune disorder is unknown, although genetics, immune system response, and environmental triggers are widely recognized as potentially contributing factors.2,3
To assess the association between physical activity and screen time in childhood with later risk of developing IBD, Tereza Lerchova, PhD, postdoctor in the department of pediatrics at the University of Gothenburg in Sweden, and colleagues, used prospectively collected data from 2 Scandinavian prospective birth cohort studies, All Babies in Southeast Sweden (ABIS) and the Norwegian Mother, Father, and Child Cohort Study (MoBa), and compared them to diagnostic records from national health registers.1
In total, the study included 65,978 participants from ABIS (n = 8810) and MoBa (n = 57,168). The primary exposure variables were the degree of physical activity and screen time as reported in both studies at ages 3 and 8 years, modeled separately as binary (high vs low) and numerical (per hour/day) variables.1
Investigators defined high physical activity as ≥2 hours per day at 3 years of age in both cohorts but noted cohort-specific cut-offs were used for the 8-year data due to differences in questionnaires and physical activity distribution between the studies. For ABIS, high physical activity was defined as ≥2 hours/day and low physical activity was defined as <2 hours/day. For MoBa, ≥1 hours/day constituted high physical activity while <1 hours/day was considered low. Cut-offs for screen time were similar between the cohorts, so high screen time was defined as ≥1 h/day and low as <1 hours/day at 3 years of age while high screen time was defined as ≥2 hours/day and low as <2 hours/day at 8 years of age for both cohorts.1
Physical activity data was available for 65,462 children 3 years of age, of whom 37% (n = 24,140) were categorized into the high physical activity group. Among the 65,345 participants with available screen time information at 3 years of age, 43% (n = 27,824) were placed in the high screen time group. At age 8, 52% (n = 19,855) of participants had high physical activity and 50% (n = 19,112) had high screen time.1
Investigators identified participants with an IBD diagnosis using linked individual-level data from the Swedish National Patient Register and the Norwegian Patient Registry. For the purpose of analysis, IBD was defined as a minimum of 2 International Classification of Diseases codes for the disease.1
During 928,981 person-years of follow-up, 266 participants, 65 from ABIS and 201 from MoBa, were diagnosed with IBD, corresponding to an incidence rate of 38.33 per 100,000 person-years in ABIS and 26.47 per 100,000 person-years in MoBa.1
In pooled analyses, high versus low physical activity at 3 years of age was not associated with the risk of IBD (adjusted hazard ratio [aHR], 1.12; 95% confidence interval [CI], 0.87–1.43) or any of its subtypes. When modeled as a numerical exposure, physical activity at 3 years of age was not associated with IBD (pooled aHR, 1.15; 95% CI, 0.95–1.39). At 8 years of age, pooled analyses revealed physical activity also was not associated with the risk of IBD (high vs low, aHR, 1.19; 95% CI, 0.80–1.76; per hour/day, aHR, 0.99; 95% CI, 0.88–1.11).1
In pooled analyses, investigators pointed out participants with high versus low screen time at age 3 years did not have a significantly increased risk of IBD (aHR, 0.91; 95% CI, 0.71–1.17) or its subtypes, with similar results observed for screen time as a numerical exposure (pooled aHR, 0.96; 95% CI, 0.81–1.14). Of note, pooled analyses for screen time at 8 years of age revealed a positive association between high screen time and later risk of IBD (aHR, 1.51; 95% CI, 1.02–2.25). An additional sensitivity analysis in which screen time was mutually adjusted to the degree of physical activity at the age 8 years showed a nearly identical result (aHR, 1.51; 95% CI, 1.01–2.25).1
“Acknowledging the presence of possible confounding variables, we found high compared to low [screen time] at age 8 years to be associated with an increased risk of subsequent IBD, while [physical activity] degree showed no such association, which motivates further prospective research in this area,” concluded investigators.1