New York, Jan 8 (IANS): Inhaling heated tobacco vapor through e-cigarettes increases chances of asthma and chronic obstructive pulmonary disease (COPD), conditions long shown to be caused by smoking traditional, combustible cigarettes.

The research data, published in the American Journal of Preventive Medicine, also suggest chances of developing COPD may be around six times greater among people who vape as well as smoke tobacco regularly, compared with those who don't use any tobacco products.

"Although e-cigarettes may turn out to be safer than traditional combustible cigarettes, our studies add to growing evidence that they carry health risks," said researcher Michael Blaha from Johns Hopkins University in the US.

Cases of asthma and COPD are rising worldwide, according to the World Health Organisation (WHO), with most cases of COPD resulting from traditional cigarettes.

To shed light on the risk, the researchers used national survey data gathered by the Behavioural Risk Factor Surveillance System in 2016-17.

In the analysis, published in BMC Pulmonary Medicine, the investigators analysed data from 402,822 people who identified themselves as never smokers -- those who smoked less than 100 combustible cigarettes in their lifetimes.

Of these, 3,103 reported using e-cigarettes or vaping, and 34,074 people reported having asthma. Almost 11 per cent of e-cigarette users reported asthma compared with eight per cent of those who had never used e-cigarettes.

The people who reported to be e-cigarette users were 39 per cent more likely to self-report asthma compared with those who said they never used e-cigarettes.

Those who said they used e-cigarettes some days were 31 per cent more likely, and daily users 73 per cent more likely to report asthma, compared with non-e-cigarette users.

For the study published in the American Journal of Preventive Medicine, the researchers analysed the same data from all the questioned participants.

Of the 700,000 plus participants, 61 per cent reported being never smokers, nine per cent current smokers, 30 per cent former smokers, more than three per cent e-cigarette users and two per cent used both e-cigarette and traditional cigarettes.

Of the e-cigarette users, about 11 per cent said they had chronic bronchitis, emphysema or COPD, compared with 5.6 per cent who said they never used e-cigarettes.

Among never smokers, e-cigarette users were 75 per cent more likely to report COPD, compared with those who had never used them.

For both studies, the researchers cautioned that they weren't designed to show that vaping directly causes lung disease, but only whether doing so was associated with an increased likelihood of having disease.