Sydney, Aug 10 (IANS): Each cigarette smoked a day by heavy smokers increases the risk of contracting several diseases by more than 30 per cent, warn researchers.

The study, which links heavy smoking with 28 separate health conditions, revealed a 17-fold increase in emphysema (chronic obstructive pulmonary disease), an 8-fold increase in atherosclerosis (clogged arteries) and a 6.5-fold higher incidence of lung cancer.

"Tobacco smoking is the leading preventable cause of death worldwide and smokers typically die 10 years earlier than non-smokers," said study researcher Elina Hypponen from the University of South Australia. "Despite a global decline in smoking over the last 20 years, an estimated 20 per cent of the world's population aged over 15 years are still smoking tobacco," Hypponen added.

In the US alone, smokers number 40 million, with 16 million of those living with a disease caused by smoking. This costs their economy more than $300 billion per annum.

According to the researchers, the most recent statistics from Australia show that about 13.8 per cent of its adult population (2.6 million people) are daily smokers. Despite a 10 per cent reduction since 1995, smoking is estimated to kill 19,000 Australians a year, accounting for nine per cent of the total burden of disease and $137 billion in annual medical costs.

For the findings, published in EClinicalMedicine, the research team analysed hospital data and mortality statistics from more than 152,483 smokers in the UK Biobank to look at how heavy smoking affects disease risks.

The researchers found the risk of suffering respiratory diseases, cancers and cardiovascular diseases increased with each cigarette smoked per day.

The link between heavy smoking and emphysema, heart disease, pneumonia and respiratory cancers was particularly high. The study also found associations with many other respiratory diseases, renal failure, septicaemia, eye disorders and complications of surgery or medical procedures.

Several known smoking outcomes, including stroke, were not identified in the study. "We only looked at how heavy smoking further affects disease risk in a group of people who are all at least past smokers, so compared to never smokers the health effects are going to be even more notable," Hypponen said.

Other factors, including when people start smoking or how long they have smoked, may also affect the health consequences arising from smoking. "Our study shows that each additional cigarette smoked matters, notably increasing the risks of cancer, respiratory, circulatory and many other diseases," the study author wrote.