Heat islands, sleepless nights and a public challenge
Rising temperatures are keeping Indians up at night. A recent study by a US-based climate advocacy group, which assessed the loss of sleeping hours in over 1,300 cities across the world, has found that the average person has lost nearly 56 hours of sleep annually between 2020 and 2025 due to unusually high night-time temperatures. At least 10 per cent of this sleep loss is directly attributable to climate change. In some of India’s largest cities, people are losing significantly more sleep than the global average, from 93 hours in Chennai to 84 hours in Mumbai and 67 hours in Delhi. As summers get longer, hotter and more humid, these findings should be seen as a warning. Sleep is often treated as an individual problem to be fixed with better lifestyle choices. But when the environment makes rest difficult, sleep becomes a public health challenge. Heat is just one of the factors that is causing Indians to toss and turn in their beds. A review of literature on sleep disorders, published last year in the Indian Journal of Public Health, found a widespread prevalence of sleep disorders across India. Sleep loss/deprivation connected to rapidly changing lifestyles, excessive screen time, social-media addiction, erratic eating habits and shift-based work schedules compound the challenges. Sleep is essential for cellular repair, immune function and regulating inflammation. Even modest reductions in sleep, when repeated over weeks or months, can have lasting effects, with chronic sleep deprivation being associated with hypertension, diabetes, heart disease, obesity and cognitive impairment, while also reducing workplace productivity and increasing the risk of accidents. India needs to recognise healthy sleep as an essential pillar of public health. Heat action plans should account not only for daytime exposure but also for dangerously warm nights, particularly in dense urban settlements where the heat island effect is strongest. Urban planning, affordable cooling solutions and better housing design all have a role. Equally important is integrating sleep health into public health campaigns. As India deals with non-communicable diseases, protecting the country’s sleep may prove to be an important investment in its long-term health.
- 1Public health is a State subject under Entry 6 of List II of the Seventh Schedule, meaning heat action plans, like the one pioneered by Ahmedabad in 2013, are designed and implemented primarily by state and municipal governments rather than the Union. The right to sleep and rest has been read by Indian courts as part of the right to life under Article 21, notably when the Supreme Court in the 2011 Ramlila Maidan case held that forcibly disturbing sleeping citizens violated their fundamental rights. Extending this reasoning, environmental conditions that chronically deprive citizens of sleep could increasingly be framed as a governance failure rather than a purely private health matter.
- 2India's National Disaster Management Authority has issued Heat Action Plan guidelines that primarily target daytime heat-wave mortality through early warning systems and cooling centres, but the editorial highlights a gap: rising night-time temperatures, driven by the urban heat island effect, receive comparatively little policy attention. Cities like Chennai, Mumbai and Delhi, shown to have the highest sleep-loss burden, also rank among India's most heat-stressed urban centres due to dense construction and reduced green cover that traps heat after sunset. Addressing this requires coordination between urban planning norms and state-level public health departments, a domestic policy integration that remains underdeveloped.
- 3The Ministry of Health and Family Welfare's National Programme on Climate Change and Human Health, aimed at building climate-resilient health systems, currently lacks specific statutory provisions addressing sleep health or night-time heat exposure standards. Building bye-laws and the National Building Code, which govern housing design and ventilation and are enforced by municipal corporations, could be revised to mandate passive cooling, an approach reflected in the Bureau of Energy Efficiency's Eco-Niwas Samhita residential energy code. Without such binding design standards, the editorial's call for 'affordable cooling solutions and better housing design' remains aspirational rather than legally enforceable.
- 4The study found the average person lost nearly 56 hours of sleep annually between 2020 and 2025 due to high night-time temperatures, but residents of Chennai lost 93 hours, Mumbai 84 hours and Delhi 67 hours, all well above the global average. Chronic sleep deprivation is scientifically linked to hypertension, diabetes, heart disease, obesity and cognitive impairment, conditions that already strain India's healthcare system given that non-communicable diseases account for over 60 percent of all deaths in the country. Reduced workplace productivity and higher accident risk from sleep loss compound these direct health costs, suggesting the economic burden of night-time urban heat extends well beyond hospital admissions.