Kolkata, Sep 26: Humans consume a wide variety of addictive substances, these addictive substances assessed quantitatively included tobacco, alcohol and illicit drugs.
Tobacco is cultivated in many regions around the world and can be legally purchased in all countries. The dried leaf of the plant nicotiana tabacum is used for smoking, chewing or snuff. Comparable data on the prevalence of smoking are not widely available and are often inaccurate, especially when age-specific data are required.
More importantly, current prevalence of smoking is a poor proxy for the cumulative hazards of smoking, which depend on several factors including the age at which smoking began, duration of smoking, number of cigarettes smoked per day, degree of inhalation, and cigarette characteristics such as tar and nicotine content or the type of filter.
To overcome this problem the smoking impact ratio, which estimates excess lung cancer, is used as a marker for accumulated smoking risk.
There were large increases in smoking in developing countries, especially among males, over the last part of the 20th century. This contrasts with the steady but slow decreases, mostly among men, in many industrialized countries.
Smoking rates remain relatively high in most former socialist economies. While prevalence of tobacco use has declined in some high income countries, it is increasing in some low and middle income countries, especially among young people and women.
Smoking causes substantially increased risk of mortality from lung cancer, upper aerodigestive cancer, several other cancers, heart disease, stroke, chronic respiratory disease and a range of other medical causes.
As result, in populations where smoking has been common for many decades, tobacco use accounts for a considerable proportion of mortality, as illustrated by estimates of smoking-attributable deaths in industrialized countries.
The first estimates of the health impacts of smoking in China and India have also shown substantially increased risk of mortality and disease among smokers. Smoking also harms others -- there are definite health risks from passive smoking and smoking during pregnancy adversely affects fetal development.
While cigarette smoking causes the majority of the adverse health effects of tobacco, chewing is also hazardous, causing oral cancer in particular, as does tobacco smoking via cigars or pipes. (UNI)