Representative image of cigarettes.
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New Delhi: Over 1.3 million lives are lost every year to cancers caused by smoking tobacco across seven countries, including India, according to a study published in The Lancet's eClinicalMedicine journal.
Researchers found that together, the seven countries -- India, China, the UK, Brazil, Russia, the US and South Africa -- represented more than half of the global burden of cancer deaths every year.
They noted that smoking, as well as three other preventable risk factors -- alcohol, obesity, and human papillomavirus (HPV) infections -- caused almost two million deaths combined.
The study, carried out by researchers from the International Agency for Research on Cancer (IARC), Queen Mary University of London (QMUL) and Kings College London, UK, also analysed the years of life lost to cancer.
The researchers concluded that the four preventable risk factors resulted in over 30 million years of life lost each year. Smoking tobacco had by far the biggest impact - leading to 20.8 million years of life being lost.
"Seeing how many years of life are lost to cancer due to these risk factors in countries around the world allows us to see what certain countries are doing well, and what isn't working," said Judith Offman, Senior Lecturer at Queen Mary University of London.
"Globally, someone dies every two minutes from cervical cancer. (Around) 90 per cent of these deaths occur in low- and middle-income countries and could be cut drastically with comprehensive screening and HPV vaccination programmes," said Offman, who worked on the study while at King's College London.
The researchers made the findings by collecting population attributable fractions of the four risk factors from previous global studies, and applied these to estimates of cancer deaths during 2020.
Preventable risk factors were associated with different cancer types in different places, they said.
For example, in India, there were more premature deaths from head and neck cancer in men, and gynaecological cancer in women, but in every other country, tobacco smoking caused the most years of life to be lost to lung cancer.
The researchers believe that this is due to differences in each of the countries.
Cervical screening is less comprehensive in India and South Africa than in other countries like the UK and the US, which would explain why there are more premature deaths from gynaecological cancers due to HPV infection in the two countries, they said.
The higher number of years of life lost to head and neck cancer in men in India could be explained by smoking habits being different to those in the UK, with the general population smoking different tobacco products, according to the researchers.
There are gender differences in the number of cancer deaths and years of life lost to different risk factors. Men have higher rates of years of life lost to smoking and drinking alcohol, because smoking and drinking rates tend to be higher in men, they said.
The study shows that in China, India and Russia, rates of years of life lost to tobacco smoking and alcohol were up to nine times higher in men than women. Being overweight or obese, and HPV infection, led to more cancer deaths and years of life lost in women than in men.
In South Africa and India, HPV led to particularly high rates of years of life lost with a large gender imbalance, they said. Rates were 60 times higher in women than men in South Africa, and 11 times higher in India, which highlights the urgent need for improved access to cervical screening and the HPV vaccination in these countries, the analysis shows.
"We know that HPV vaccination prevents cervical cancer. This, coupled with cervical screening, could eliminate cervical cancer as a public health problem. Countries need to come together on this ambition," Offman added.