Later sunsets reduce children's sleep, harming their learning and long-term education outcomes in India.
In the global discourse on education and child development, factors like school quality, teacher training, and curriculum often take centre stage. However, an essential element—sleep—remains underexplored, especially in low-income countries. While sleep medicine literature emphasises that adequate sleep is crucial for attention, memory, and cognition (Killgore 2010, Lim and Dinges 2010), there's a significant gap in understanding how sleep affects children's educational outcomes both in the long-run and in developing country contexts.
Sleep and cognitive function: What we know
Research in high-income countries has established that sleep deprivation impairs cognitive performance in adults (Banks and Dinges 2007, Van Dongen and Dinges 2005). Studies leveraging variations in sunset times, time zones, and daylight-saving time transitions have linked adult sleep loss to decreased wages (Gibson and Shrader 2018), impaired cognitive skills (Giuntella et al. 2017), and adverse health outcomes (Giuntella and Mazzonna 2019).
However, counter to results from rich countries, experimental evidence from the lower-income countries indicates that increasing adult sleep has no detectable effects on cognition or productivity in India, plausibly due to poor sleep quality in this setting (Bessone et al. 2021). These results caution against extrapolating sleep-science findings across diverse contexts.
For children, some studies suggest that sleep deprivation negatively affects cognition (Lo et al. 2016), but these findings are primarily from laboratory settings in developed countries. These studies often lack real-world applicability and focus on short-term effects, leaving a gap in understanding on long-term educational impacts (Beebe 2016).
Investigating sleep's impact on Indian children between the ages of six and sixteen
My recent study aims to fill this gap by examining how sleep affects children's educational outcomes in India, a context where children often face challenging living conditions that can disrupt sleep. Nearly 75% of Indian households live in two rooms or less, with an average family size of five (Census of India 2011). Overcrowding, noise, and heat can contribute to poor sleep quality, potentially diminishing the cognitive benefits of sleep.
Using data from the 1998-99 Indian Time Use Survey (ITUS), I analysed how variations in sunset times affect children's sleep and daily activities. The ITUS provides detailed 24-hour time use data, allowing us to assign sunset times at the district and interview-date level. By exploiting seasonal variations in daily sunset times and controlling for fixed district characteristics and seasonal confounders, I isolated the impact of sunset-induced sleep changes on children's behaviour.
Key findings: Later sunsets mean less sleep and lower learning
Our analysis reveals that an hour delay in sunset time reduces children's sleep by approximately 30 minutes. Children tend to go to bed later when the sun sets later but do not compensate by waking up later, likely due to fixed morning schedules.
This reduction in sleep has tangible consequences. Sleep-deprived children spend less time on homework or studying, indicating that reduced sleep leads to decreased study time. Interestingly, there is a minimal and imprecisely estimated effect on time spent on formal or informal work, suggesting that sleep loss does not significantly alter children's labour activities.
These results are consistent with a model where sleep is more study-productivity enhancing than labour-productivity enhancing. In other words, adequate sleep seems to be more critical for activities that require cognitive effort, like studying, rather than for labour tasks.
To compensate for lost nighttime sleep, children increase daytime naps and spend more time on indoor leisure activities. These behavioural adjustments imply that children prioritise rest and leisure over study when they are sleep-deprived.
Using the Young Lives Survey (YLS) from the Andhra Pradesh, I found that a 10-minute delay in sunset time reduces math test scores by roughly 0.1 standard deviations. This effect persists even after controlling for individual characteristics and comparing the same children over different survey rounds, reinforcing the robustness of these findings.
Long-term effects are equally concerning. Data from the 2015 India Demographic and Health Survey (DHS) indicate that a 10-minute delay in annual average sunset time reduces children's years of education by 0.14 years. Children exposed to later sunsets are less likely to complete primary and middle school, highlighting the enduring impact of sleep deprivation on educational attainment.
Sleep is an important input into the education production function
Our findings suggest that sleep is a crucial, yet overlooked input in the education production function, particularly in low-income settings like India. Interventions aimed at improving sleep—such as modifying school start times (Heissel and Norris 2017, Carrell et al. 2011) or improving sleep environments—could have significant benefits for children's educational outcomes.
Given that sleep deprivation leads to reduced study time and lower test scores, policies should consider the timing of school schedules relative to natural light patterns. Additionally, addressing environmental factors that disrupt sleep, such as heat and noise, could increase child sleep duration and, by extension, cognitive function.
Raising educational outcomes through adequate sleep
Sleep is more than just a basic biological need; it's a fundamental component of children's ability to learn and succeed academically. As policymakers and educators strive to improve educational outcomes in India and other low-income countries, incorporating strategies to ensure adequate sleep could play a pivotal role.
References
Banks, S, and D F Dinges (2007), “Behavioral and physiological consequences of sleep restriction,” Journal of Clinical Sleep Medicine, 3(5): 519–528.
Beebe, D W (2016), “The cumulative impact of adolescent sleep loss: Next steps,” Sleep, 39(3): 497–499.
Bessone, P, A Rao, G Schilbach, H Schofield, and S Toma (2021), “The economic consequences of increasing sleep among the urban poor,” The Quarterly Journal of Economics, 136(3): 1887–1941.
Carrell, S E, T Maghakian, and J E West (2011), “A’s from Zzzz’s? The causal effect of school start time on the academic achievement of adolescents,” American Economic Journal: Economic Policy, 3(3): 62–81.
Census of India (2011), “Houses, household amenities and assets,” Government of India.
Gibson, M, and J Shrader (2018), “Time use and productivity: The wage returns to sleep,” Review of Economics and Statistics, 100(5): 783–798.
Giuntella, O, W Han, and F Mazzonna (2017), “Circadian rhythms, sleep, and cognitive skills: Evidence from an unsleeping giant,” Demography, 54(5): 1715–1742.
Giuntella, O, and F Mazzonna (2019), “Sunset time and the economic effects of social jetlag: Evidence from US time zone borders,” Journal of Health Economics, 65: 210–226.
Heissel, J, and S Norris (2017), “Rise and shine: The effect of school start times on academic performance from childhood through puberty,” Journal of Human Resources, Forthcoming.
Killgore, W D S (2010), “Effects of sleep deprivation on cognition,” Progress in Brain Research, 185: 105–129.
Lim, J, and D F Dinges (2010), “A meta-analysis of the impact of short-term sleep deprivation on cognitive variables,” Psychological Bulletin, 136(3): 375–389.
Lo, J C, F M Ong, S J Leong, W S Gooley, and M W Chee (2016), “Cognitive performance, sleepiness, and mood in partially sleep deprived adolescents: The need for sleep study,” Sleep, 39(3): 687–698.
Van Dongen, H P A, and D F Dinges (2005), “Sleep, circadian rhythms, and psychomotor vigilance,” Clinics in Sports Medicine, 24(2): 237–249.