The Impact of Tobacco Use and/or Body Composition on Adult Mortality in Urban Developing Country Population. Results from the Mumbai Cohort Study, Mumbai, India, 1991-2003

Abstract

Tupakka ja ravitsemus ovat maailmanlaajuisia kansanterveysongelmia ja niiden arvioidaan aiheuttavan noin viidenneksen kaikista kuolemista. Intian suurimmassa kaupungissa Mumbaissa haastateltiin 150 000 aikuista heidän elin- ja tupakointitavoistaan. Heitä seurattiin keskimäärin 5,5 vuotta ja selvitettiin kuolemantapaukset ja niiden syyt.

Intiassa tupakkaa käytetään yleisesti ja monessa muodossa. Tupakanpoltto oli tavallista vain miehillä ja muut tupakointimuodot (savuttomat) olivat yleisiä molemmilla sukupuolilla. Intialaiset savukkeet olivat yhtä haitallisia kuin länsimaiset. Myös muut tupakointitavat aiheuttivat huomattavan ylikuolleisuuden.

Ravitsemustilaa mitattiin painoindeksillä. Yli- ja alipainoisia oli lähes yhtä paljon, mutta selvä laihuus oli selvää lihavuutta tavallisempaa. Ylipainoisten kuolleisuus oli pienintä ja vasta lihavilla esiintyi ylikuolleisuutta normaalipainoisiin verrattuna. Alipainoisilla kuolleisuus oli suurentunutta ja kasvoi sen mukaan, mitä laihemmista oli kyse.

Miehillä tupakoinnin ja laihuuden yhteisvaikutus oli toisiaan voimistavaa, kun taas tupakointi ja lihavuus vaimensivat toistensa vaikutusta. Naisilla yhteisvaikutukset olivat toisiaan vaimentavia mutta tupakan kulutus oli lähinnä savutonta.

Ylipainosta on kehittynyt yksi länsimaiden pahimpia terveyden vaaratekijöitä. Intiassa laihuus eli aliravitsemus on edelleen ensisijaisempi. Intia kuitenkin länsimaistuu nopeasti ja on mahdollista, että maassa tulee olemaan kahdensuuntainen eli sekä laihuuteen että lihavuuteen liittyvä terveysongelma, jota yleiset ja monimuotoiset tupakointitavat lisäävät.

Worldwide, there are two important risk factors underlying the major causes of death, tobacco use and nutritional status. Of the total 55.9 million global annual deaths, tobacco use and nutritional status, together, account for approximately 20%. Information about excess mortality from different forms of tobacco use other than cigarette smoking (such as bidi smoking and the various forms of smokeless tobacco use), is very limited. Using Mumbai Cohort Study (MCS) data from India, the present study reports on the association of various kinds of tobacco habits that are prevalent in India with all-causes of mortality and with major causes [such as cancers, tuberculosis (TB), etc.].

Nutrition research in India has focused primarily on the problem of undernutrition, particularly among vulnerable women and children. Currently, India is undergoing a rapid economic transition. At this stage in the associated epidemiologic transition, the country is facing the double burden of communicable and non-communicable diseases. In all such transitions, nutrition plays a central role.

The joint effect of tobacco use (mainly smoking) and body mass on mortality has not been well characterized, although a body of evidence is accumulating on the individual effect of smoking on the association of body mass and mortality. Using MCS, this was the first such attempt, from a developing country population, where both under- and over- nutrition and tobacco use are major public health concerns. Using the Mumbai electoral role list as the selection frame, a total of 148,173 individuals aged ≥ 35 years were recruited (1991 1997) for a prospective follow-up study. After an average 5.5 years an active house-to-house follow-up (to ascertain vital status) was conducted (1997 2003).

At active follow-up, 140,908 (95%) individuals were traced. Among these, 13,261 deaths were recorded, of which 85% occurred within the study area. It was possible to abstract cause of death information from Bombay Municipal Corporation death registers for 9,259 deaths.

All forms of tobacco smoking increased the risk of dying in Mumbai. In addition to smoking, different forms of smokeless tobacco use also resulted in excess mortality. Using MCS findings, a total of 24% male and 6% female deaths (aged 35 69 years) were found to be attributable to their tobacco usage. Also, 41.6% of men s and 20.7% of women s cancer deaths were found to be attributable to their tobacco usage. Bidi smoking was found to be as harmful as cigarette smoking and was found to be responsible for around 32% of TB deaths.

Therefore, MCS findings provide supportive evidence from the population of a developing country about the association of tobacco usage with increased risk of death; primarily for various cancers and TB. MCS results showed that both chronic underweight and overweight are equally present in an urban population of India. However, the important public health implications for the burden of diseases are associated with only the upper extreme (obese) and all underweight body composition (BC). The results from MCS highlight the immediate need to identify and to address both underweight and obese portions of the distribution in identifying vulnerable targeting interventions.

Our study reported that tobacco use is a risk factor for low BMI. Further, tobacco use and low BMI had synergistic effect on mortality in men and antagonistic effect in women, independent of whether additive or multiplicative interaction was assumed. Tobacco use and undernutrition are known to be serious problems in India, and the present study indicates that obesity may emerge as a serious public health problem. However, the effect of obesity on mortality is subject to large random variation in this study.

The policy implications for prevention would be that improving the nutritional status of those underweight and preventing use of tobacco results in the immediate highest yield.