Increased risk for excessive weight gain in infants who sleep less than 12 hours per 24 hours

“One out of every three Americans weigh as much as the other two.”

—Richard Jeni, A Big Steaming Pile of Me

Results from the 2017–2018 National Health and Nutrition Examination Survey reported that 19.3% of U.S. children and adolescents aged 2–19 years are obese (body mass index [BMI] above the 95th percentile), including 6.1% with severe obesity (BMI > 120th percentile) and another 16.1% who are overweight (BMI > 85th percentile).¹ The prevalence of obesity nearly tripled between 1971–1974 and 2017–2018, increasing from 5.0%–13.4% among those ages 2–5 years, 4.0%–20.3% among those ages 6–11 years, and 6.1%–21.2% among those ages 12–19 years.¹

A potent risk for obesity across the lifespan is rapid weight gain (> 0.67 positive change in weight-for-age z score), especially when it occurs in the first 6 months of life.^2–7 A 2020 study of 17,002 children found that rapid weight gain most often occurs between ages 0 and 6 months (17.5%) vs 18–24 months (1.8%) and increases the risk of being overweight/obese at age 3 years by 2.6-fold.³ The Generation R study showed that rapid weight gain between ages 0 and 3 months was associated with a higher percentage of body fat, more central adiposity, and reduced insulin sensitivity in early adulthood.⁸ Rapid weight gain within the first 6 months of life has been shown to increase risks for obesity, diabetes, metabolic syndrome, and cardiovascular disease across the lifespan.^9,10

Many health care professionals know that short sleep duration increases the risk for obesity in children and adolescents.¹¹ However, fewer may know that sleeping less than 12 hours/24 hours during the first 6 months of life predisposes to overweight/obesity across one’s entire life. Short sleep duration in 1,679 infants at age 3 months (but not at ages 8, 18, or 24 months) was associated with a 2.6-fold increased risk for excessive weight gain between ages 3 and 24 months.¹² Sleeping <12 hours/24 hours at age 2 months in 5,161 infants predicted a higher BMI and fat mass at age 6.¹³ Another prospective study found that sleeping < 12 hours/24 hours during infancy among 915 children was associated with a greater BMI z score and a 2-fold increased odds of being overweight/obese at age 3 even after adjusting for multiple confounders (including race/ethnicity, television-watching, active play, breastfeeding).¹⁴

A particularly interesting prospective longitudinal study by Yu et al,¹⁵ published in this issue of the Journal of Clinical Sleep Medicine, investigated whether short sleep duration in 186 healthy monozygotic and dizygotic twin pairs during infancy correlated with excessive weight gain in childhood. They found that the 186 healthy twin pairs who slept < 12 hours per 24 hours at age 6 months were 3.47 times more likely to gain excessive weight between ages 6 and 18 months. The authors further found that the association between sleep restriction and excessive weight gain was more pronounced in monozygotic than dizygotic twins, suggesting that the relationship may be more strongly affected by genetic factors than a shared environment. The Yu et al. study which began in China in 2016 is the first prospective study of short sleep duration in early infancy in twins.

Twin studies provide a natural model for investigating how genetics and shared environment impact on sleep duration. Twin pairs (save those separated at birth) share genetics, birth mother, age, intrauterine environment, upbringing, eating behaviors, outdoor activities, and screen time. Only a few studies have examined the relationships between sleep duration and genes, environment in twins, twins but not when they were infants.¹⁷ One study of 995 twin pairs followed between ages 6 and 48 months found strong genetic influences for nighttime sleep duration, whereas environment shaped daytime sleep duration.¹⁶ Another study in 1,931 twin pairs at age 15 months found that the shared environment predominantly influenced both daytime and nighttime sleep duration with only modest genetic effects.¹⁷

Two decades of human and animal studies show that the risk for obesity (and type 2 diabetes) begins even earlier in the womb with intrauterine epigenetic metabolic programming.¹⁸ For example, maternal smoking during pregnancy has been linked to an increased risk of low birth weight in infants who later become overweight/obese^19–21 and is related to DNA methylation at a specific gene (GF11).²²

Being cognizant of the importance of sufficient sleep duration in addressing obesity in infants, how can we intervene? A 2018 meta-analysis of children from birth–age 3 years found that the BMI z score decreased for every 1 hour increase in total sleep.¹² A 2021 randomized controlled trial found that napping ≥ 5 times/day at age 1 month was significantly associated with a 0.11 odds ratio of the child being overweight at age 3 years.⁵ A recent study showed that putting infants ages 6–24 weeks to bed consistently 1 hour earlier than their usual sleep onset time resulted in an average of 34 minutes more sleep per night.²⁴

Several prospective studies are encouraging parents to help infants acquire healthier sleep habits, move more, and spend less time in the car seat; avoid using food as reward or punishment (response feeding); breastfeed rather than use formula; and avoid electronic screen exposure before age 18 months.^25–29 Particularly intriguing is the Snuggle Bug/Acurrucadito study investigating the influence of sleep/wake patterns on gut microbiome development and rapid weight gain in infancy.²⁹ Increases in the abundance of Bifidobacteria species at age 3 months and Staph aureus at ages 6 and 12 months are associated with being overweight at age 10 years.³⁰

We must not forget that lifelong obesity is perpetuated by the easy availability of highly processed sugar-laden food coupled with innovative electronic technologies that promote sedentary predilections while providing enjoyment. Given these challenges, health care professionals need a host of strategies to stem the tsunami of childhood obesity, worthy of herculean efforts given obesity’s lifelong shadow on health.

DISCLOSURE STATEMENT

This was not an industry-sponsored project. The author reports no conflicts of interest related to this editorial, and no investigational or off-label use is discussed.