The world health report

Chapter 4

Addictive substances

Humans consume a wide variety of addictive substances. The addictive substances assessed quantitatively in this report included tobacco, alcohol and illicit drugs (see Table 4.5). Some summary results are shown in Figure 4.6a and Figure 4.6b .

Smoking and oral tobacco use

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 (24,25). 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 a 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 (26). 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 (27,30). Smoking also harms others -- there are definite health risks from passive smoking (see Box 4.1) 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.

Box 4.1 Environmental tobacco smoke

Environmental tobacco smoke (ETS) is a combination of exhaled smoke from active smokers and the smoke coming from smouldering tobacco between puffs. Also known as second-hand smoke or passive (involuntary) smoking, ETS causes disease in non-smokers; it contains all the same toxic components as mainstream tobacco smoke, although in somewhat different relative amounts.

ETS exposure is primarily dependent on the prevalence of smoking, including both commercial and non-commercial forms of tobacco. In addition, smoking intensity (the amount of tobacco smoked per smoker), differences in ventilation, and differences in places where people smoke affect the amount of ETS exposure that results per smoker.

Most studies on the health effects of ETS have focused on household and occupational exposures. People are also exposed in other environments, such as schools, transport systems, bars and restaurants. Exposure to ETS has been associated with lower respiratory infections, sudden infant death syndrome, asthma, ischaemic heart disease, otitis media, lung cancer and nasal-sinus cancer. In the United States, for example, several thousand lung cancer deaths are associated with ETS exposure each year. There is increasing evidence that ETS causes heart disease and in the United States alone it has been estimated to cause tens of thousands of premature deaths each year. There is evidence that even short-term exposures to ETS can increase the risk of coronary thrombosis by increasing blood platelet aggregation.

In addition, maternal smoking during pregnancy results in passive smoke exposure for the fetus (sometimes referred to as tertiary smoke), resulting in an increased risk of low birth weight and sudden infant death syndrome. The risk of sudden infant death syndrome is doubled when mothers smoke.

Protecting people from ETS exposure has a large role in policy debates about controlling active smoking, since ETS exposures affect not only smokers but also others around them, most importantly young children who are not in a position to protect themselves. Without major efforts to bring smoking and ETS exposure under control, the burden of disease from ETS will continue to increase in the future.

Sources: (31,38).

Among industrialized countries, where smoking has been common, smoking is estimated to cause over 90% of lung cancer in men and about 70% of lung cancer among women. In addition, in these countries, the attributable fractions are 56--80% for chronic respiratory disease and 22% for cardiovascular disease. Worldwide, it is estimated that tobacco causes about 8.8% of deaths (4.9 million) and 4.1% of DALYs (59.1 million). The rapid evolution of the tobacco epidemic is illustrated by comparing these estimates for 2000 with those for 1990: there are at least a million more deaths attributable to tobacco, with the increase being most marked in developing countries. The extent of disease burden is consistently higher among groups known to have smoked longest -- for example, attributable mortality is greater in males (13.3%) than females (3.8%). Worldwide, the attributable fractions for tobacco were about 12% for vascular disease, 66% for trachea bronchus and lung cancers and 38% for chronic respiratory disease, although the pattern varies by subregion. Approximately 16% of the global attributable burden occurred in WPR-B, 20% in SEAR-D and 14% in EUR-C.

Alcohol use

Alcohol has been consumed in human populations for millennia, but the considerable and varied adverse health effects, as well as some benefits, have only been characterized recently (39,40). Alcohol consumption has health and social consequences via intoxication (drunkenness), dependence (habitual, compulsive, long-term heavy drinking) and other biochemical effects. Intoxication is a powerful mediator for acute outcomes, such as car crashes or domestic violence, and can also cause chronic health and social problems. Alcohol dependence is a disorder in itself. There is increasing evidence that patterns of drinking are relevant to health as well as volume of alcohol consumed, binge drinking being hazardous.

Global alcohol consumption has increased in recent decades, with most or all of this increase occurring in developing countries. Both average volume of alcohol consumption and patterns of drinking vary dramatically between subregions. Average volume of drinking is highest in Europe and North America, and lowest in the Eastern Mediterranean and SEAR-D. Patterns are most detrimental in EUR-C, AMR-B, AMR-D and AFR-E. Patterns are least detrimental in Western Europe (EUR-A) and the more economically established parts of the Western Pacific region (WPR-A).

Overall, there are causal relationships between average volume of alcohol consumption and more than 60 types of disease and injury. Most of these relationships are detrimental, but there are beneficial relationships with coronary heart disease, stroke and diabetes mellitus, provided low-to-moderate average volume of consumption is combined with non-binge patterns of drinking. For example, it is estimated that ischaemic stroke would be about 17% higher in AMR-A, EUR-A and WPR-A subregions if no-one consumed alcohol.

Worldwide, alcohol causes 3.2% of deaths (1.8 million) and 4.0% of DALYs (58.3 million). Of this global burden, 24%occurs in WPR-B, 16% in EUR-C, and 16% in AMR-B. This proportion is much higher in males (5.6% of deaths, 6.5% of DALYs) than females (0.6% of deaths, 1.3% of DALYs). Within subregions, the proportion of disease burden attributable to alcohol is greatest in the Americas and Europe, where it ranges from 8% to 18% of total burden for males and 2% to 4% for females. Besides the direct effects of intoxication and addiction resulting in alcohol use disorders, alcohol is estimated to cause about 20--30% of each of the following worldwide: oesophageal cancer, liver cancer, cirrhosis of the liver, homicide, epilepsy, and motor vehicle accidents. For males in EUR-C, 50--75% of drownings, oesophagus cancer, epilepsy, unintentional injuries, homicide, motor vehicle crashes and cirrhosis of the liver are attributed to alcohol.

Illicit drug use

Illicit drug use includes the non-medical use of a variety of drugs that are prohibited by international law. The current analysis focuses on the burden attributable to the injection of amphetamines and opioids, including cocaine and heroin. Other illegal drugs, such as ecstasy, solvents and cannabis have not been included because there is insufficient research to quantify their health risks globally.

Because the use of these drugs is illicit and often hidden, it is difficult to estimate the prevalence of their use and the occurrence of adverse health consequences. Despite these difficulties, it is apparent that illicit drugs cause considerable disease burden and their use is increasing in many countries, including those with little past history of such use (41,42).

The estimated prevalence of illicit drug use varies considerably across WHO regions. For example, estimates from the United Nations Drug Control Programme of the prevalence of opioid use in the past 12 months among people over the age of 15 years varies by an order of magnitude or more, from 0.02--0.04% in the Western Pacific region to 0.4--0.6% in the Eastern Mediterranean region. Cocaine use varies to a similar extent, but the prevalence of amphetamine use is estimated to be 0.1%--0.3% in most regions.

The mortality risks of illicit drugs increase with frequency and quantity of use (43,44). The most hazardous patterns are found among dependent users who typically inject drugs daily or near daily over periods of years. Studies of treated injecting opioid users show this pattern is associated with increased overall mortality, including that caused by HIV/AIDS, overdose, suicide and trauma. Other adverse health and social effects that could not be quantified include other bloodborne diseases such as hepatitis B and hepatitis C, and criminal activity associated with the drug habit.

Globally, 0.4% of deaths (0.2 million) and 0.8% of DALYs (11.2 million) are attributed to overall illicit drug use. Attributable burden is consistently several times higher among men than women. Illicit drugs account for the highest proportion of disease burden among low mortality, industrialized countries in the Americas, Eastern Mediterranean and European regions. In these areas illicit drug use accounts for 2--4% of all disease burden among men.