The study by Energy Policy Institute at the University of Chicago (EPIC)showed that this is because air quality fails to meet the World Health Organization's (WHO) guideline for fine particulate pollution.
A 72 per cent increase in pollution from 1998 to 2016 in the region that is home to about 40 per cent of India's population.
In 1998, the impact on people's lives would have been half of what it is today, with residents losing 3.7 years of life expectancy.
In 1998, citizens living outside of the Indo-Gangetic plain region would have seen their lives cut short by 1.2 years relative to what it would have been if air quality met the WHO guideline.
That number has grown to 2.6 years, also worsening but much more modest than what has taken place in the Indo-Gangetic plain.
The findings were announced as the full platform of the AQLI was made accessible in Hindi, expanding the Index's ability to inform citizens and policymakers about particulate air pollution the greatest threat to human health globally.
"With the addition of this Hindi version, hundreds of millions more users will be able to learn how particulate pollution is affecting their lives, and, importantly, how air pollution policies can make an enormous difference in increasing life expectancy," said Michael Greenstone, the Milton Friedman Distinguished Service Professor in Economics and director of EPIC.
If India is successful in meeting its goals under the National Clean Air Programme, and sustaining pollution reductions of about 25 per cent, the AQLI shows that such improvements in air quality would extend the life expectancy of the average Indian by 1.3 years.
Those in the Indo-Gangetic plain would gain about two years onto their lives.
Speaking at the Hindi AQLI launch event here, Member of Parliament Gaurav Gogoi said, "I am working towards introducing a private member's bill to come up with a new clean air (amendment) act where health impacts of air pollution is given the top priority."
The AQLI is rooted in a pair of peer-reviewed studies in which Greenstone and his co-authors exploited a unique natural experiment in China based on China's Huai River Winter Heating policy.
The natural experiment allowed them to isolate the effect of air pollution from other factors that affect health, and to do so at the very high concentrations that prevail in India and other countries today.
They then combined the results from these studies with hyper-localized, global particulate matter measurements, allowing users to zoom in on any district in the world and understand the impacts of that district's local air pollution on life expectancy.
( With inputs from IANS )