A lot of homes in crowded cities like Chennai and Bangalore are tightly packed, congested and poorly ventilated. Air (dust) and noise (human activity) pollution is very high. Within the same congested dwelling, there maybe people who have to get up very early and go to work or come home late and sleep late which disrupts everyone's sleep. So it is highly likely that there is only 4-5 hour window at night when things are quiet enough to get good sleep.