Mortalidad atribuible al tabaquismo en Bangladesh: estudio de mortalidad proporcional

Introduction Deaths attributable to smoking are projected to increase substantially throughout the 21st century and much of the increase will occur in low- and middle-income countries (1) such as Bangladesh, whose population of 150 million makes it the seventh most populous country in the world. More than half of Bangladeshi men over the age of 25 years smoke cigarettes or bidis, small handmade cigarettes containing about one fourth the amount of tobacco found in cigarettes. (2) A nationally representative case-control study in neighbouring India showed that in 2010 smoking caused about 20% of all deaths among males aged 30 to 69 years. (3) Smoking cessation rates are relatively low in Bangladesh and India, (2) but Bangladeshi men are, on average, younger than Indian men when they start smoking and they smoke more cigarettes or bidis daily than Indian men. (2,4) Bidis account for most of the tobacco smoked in India, but in Bangladesh cigarettes represent about half of all the tobacco smoked. According to recent studies in high-income countries, men and women who start smoking as young adults and do not quit have a threefold risk of dying relative to those who have never smoked. (5,6) Prospective studies are required to determine whether the same extreme risks hold true for Bangladesh and other low- and middle-income countries. Of the estimated 21.9 million smokers in Bangladesh, 21.2 million are males and only 0.7 million are females. Thus, only the effects of smoking among men can be reliably studied at present. The objective of this study was to assess the effects of smoking on cause-specific mortality among Bangladeshi men between the ages of 25 and 69 years. We conducted a retrospective case-control study using data on cause of death and smoking status for all men in this age group who died in the subdistrict of Matlab in rural Bangladesh between 2003 and 2010. Although tobacco chewing is common in Bangladesh, its effects will be reported in a separate paper since chewing causes fewer diseases than smoking, most notably oral cancer. (7) Methods Study design As part of the INDEPTH Network, the International Centre for Diarrhoeal Disease Research, Bangladesh (icddr, b), has maintained a comprehensive Health and Demographic Surveillance System (HDSS) in Matlab, in the district (zilla) of Chandpur, since 1966. (8,9) Matlab is a rural area (upazila) located about 55 km south-east of Dhaka, the capital city. It covers 184 [km.sup.2] and has 142 villages, each with about 1500 people. The total population of Matlab is about 225 000. To track fatal events as part of the HDSS, trained field research assistants visit households where a death has occurred from 6 to 12 weeks after the death and administer a structured verbal autopsy questionnaire to any relative who lived with the deceased. The purpose is to obtain from these respondents information on the symptoms, signs and medical details surrounding the death. Field staff are instructed not to try to arrive at a diagnosis of the cause of death. Instead, causes of death are assigned by two trained physicians at icddr, b in accordance with the International statistical classification of diseases and related health problems, tenth revision (ICD-10) and using standardized disease coding guidelines developed for other INDEPTH sites. (8,10) Subjects Cases were men aged 25 to 69 years of age who had died from causes strongly associated with tobacco smoking: (1,7,11) cancers of the lung, mouth and larynx (ICD-10 codes: C00-14, C32-34); cancers of the digestive organs (C16-26, C48, D01, D12-13); all other cancers (rest of C00-D48, excluding C60-63 and C69-72); chronic lower respiratory diseases (J40-47); pulmonary tuberculosis (A 15-19 ); all other respiratory diseases (rest of J00-99); stroke (I60-64); ischaemic heart disease (I20-25); all other vascular diseases (rest of 100-99); cirrhosis (K70-77); and other medical causes (rest of A00-R99, excluding the diseases not associated with tobacco smoking, which were the causes of death among controls). …