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.
- 1The Supreme Court has progressively expanded Article 21's right to life to encompass a right to a healthy environment and, by extension, public health protections, as seen in M.C. Mehta v. Union of India and Consumer Education and Research Centre v. Union of India (1995), providing a constitutional hook for climate-linked health harms like heat-driven sleep loss to be framed as a fundamental rights issue rather than a mere policy inconvenience.
- 2Globally, heat-health governance is increasingly tied to international climate commitments, since India's Nationally Determined Contributions under the Paris Agreement of 2015 include adaptation components, and the World Health Organization has flagged heat stress as a growing transboundary public health emergency requiring coordinated city-level responses, similar to the 1,300-city study referenced in the editorial.
- 3India's primary legal-institutional response to extreme heat operates through state and municipal Heat Action Plans, pioneered by Ahmedabad in 2013 following a deadly 2010 heatwave, and now mandated by the National Disaster Management Authority guidelines under the Disaster Management Act, 2005, which classifies heatwaves as a notified disaster in several states, triggering specific administrative and funding obligations.
- 4The cited study found Indians in Chennai lose 93 hours of sleep annually, Mumbai residents lose 84 hours, and Delhi residents lose 67 hours, all above the global average of 56 hours, while chronic sleep deprivation is linked to conditions like hypertension and diabetes that already affect over 200 million and roughly 100 million Indians respectively according to recent national health surveys, underscoring the scale of the public health stakes involved.