Scientists link smoking to five more diseases making it deadlier than ever
Research has already linked smoking to 21 diseases including 12 types of cancer, six categories of cardiovascular disease including coronary heart disease and stroke, diabetes, chronic obstructive pulmonary disease [COPD], and pneumonia.
Now, scientists at the Washington University School of Medicine have indicated that smoking is also linked to significantly increased risks of infection, kidney disease and renal failure, intestinal disease caused by inadequate blood flow, and heart and lung illnesses not previously attributed to tobacco.
In the new study, funded by the American Cancer Society, the researchers looked at health data from almost one million people over a 10-year period.
Their findings suggest that the number of people dying from smoking every year worldwide is significantly underestimated.
Health officials estimate that smoking kills around 480,000 people each year in the United States.
In the United Kingdom, the figure is around 100,000, while the World Health Organisation (WHO) estimates the global figure stands at six million when factoring in second-hand smoke.
The Washington University research team nevertheless believes that all those figures could be considerably higher when taking into account deaths from the five additional health problems they now link to smoking.
Co-author of the study, Dr Eric Jacobs, estimates smoking could be killing around 60,000 extra Americans annually, or around 13 percent of the 480,000 deaths currently attributed to the habit each year.
When applied to the worldwide figure, their theory suggests an extra 780,000 could be dying every year from the effects of smoking.
Participants in the study, which was published in the New England Journal of Medicine, were men and women aged 55 or over.
More than 180,000 of the participants died over the course of the decade-long study, with current smokers, as predicted, experiencing death rates almost three times higher than those who had never smoked.
The findings showed that the majority of deaths in smokers were due to diseases that are established as being caused by smoking.
They nevertheless also showed that around 17 percent of the excess deaths in smokers were due to diseases that have not yet officially been linked to smoking by the US surgeon general. Consequently, these deaths would not have been counted in estimates of the death toll from smoking.
The researchers noted that smoking was found to at least double the risk of death from several causes, including renal failure, intestinal ischemia, hypertensive heart disease, infections and various respiratory diseases other than COPD.
Smokers were also six times more likely to die from a rare illness caused by insufficient blood flow to the intestines.
Smoking was also linked with smaller increases in risk of death from other causes not formally recognised as caused by smoking including breast and prostate cancer.