24 August 2009

Smoking ups malnutrition, TB risk

One study found that smokers finance their habit by with the family food budget, while another links smoking to an increased risk of TB, highlighting the high cost of smoking.


A new study finds that smokers in rural Indonesia finance their habit by dipping into the family food budget—which ultimately results in poorer nutrition for their children. The findings suggest that the costs of smoking in the developing world go well beyond the immediate health risks, according to authors Steven Block and Patrick Webb of Tufts University.

The study is published in Economic Development and Cultural Change.

Using surveys of 33 000 mostly poor households in Java, Indonesia, the researchers found that the average family with at least one smoker spends 10% of its already tight budget on tobacco. Sixty-eight percent of a smoking family's budget goes to food, and 22% for non-food, non-tobacco purchases. The average non-smoking family, on the other hand, spends 75% of its income on food and 25% for non-food items.

"This suggests that 70% of the expenditures on tobacco products are financed by a reduction in food expenditures," the researchers write.

That decreased spending on food appears to have real nutritional consequences for children of smokers. The study found that smokers' children tend to be slightly shorter for their ages than the children of non-smokers. Height is often used by health researchers as a general barometer for nutrition in children.

The decrease in child nutrition associated with a parent who smokes is "an intuitive but rarely documented empirical finding," the researchers write.

Increasing number of smokers threatens developing nations
The poorer nutrition in smoking families comes not only because they buy less food in total, but also because the food they buy tends to be of lower quality. The surveys show that, compared to non-smoking families, families with a smoker spend a larger budget share on rice and a smaller share on meats, fruits and vegetables, which are nutrient-rich, but more expensive.

Nearly 60% of Indonesian men smoke. Rates are similarly high—and increasing—in other developing Asian nations. Block and Webb's research suggests that these increasing rates pose a dual threat to developing nations.

"The combination of direct health threats from smoking coupled with the potential loss of [food] consumption among children linked to tobacco expenditure presents a development challenge of the highest order," the researchers conclude.

Second study finds smoking a risk factor for TB
Meanwhile another study found that smoking is a risk factor for active tuberculosis (TB) disease, according to a new study on TB incidence in Taiwan.

The research analysed data from nearly 17 000 individuals in Taiwan as part of Taiwan's 2001 National Health Interview Survey (NHIS).

While past studies have reported increased mortality among TB patients who smoke, none have been able to specifically examine the direct effect of smoking on active TB incidence using a longitudinal design in a general population. "In this prospective cohort study we found a two-fold increase in the risk of active TB in current smokers compared with never-smokers," said lead author, Hsien-Ho Lin, postdoctoral research fellow from Brigham and Women's Hospital, in Boston.

The results are reported in the American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society.

Dr Lin and collaborators retrieved information from the individual NHIS records on smoking data and exposure to second-hand smoke at home. They also identified potential confounders, including sex, age, living in a crowded home, household income, marital status, alcohol use and employment.

They then identified all incident cases of TB occurring between 2001 and 2004 by using that National Health Insurance database.

How the study was done
When they compared the likelihood of active TB among ever-, never-, and current smokers, they found that ever-smokers had 2.69 times the risk of developing active TB than never-smokers; current smokers had 2.73 times the risk. After adjusting for potential confounders, the increased risk remained significant for current smokers, who had twice the risk of developing active TB in comparison to never-smokers.

Interestingly, they also found that younger smokers were more likely than smokers older than 65 to develop active TB relative to their non-smoking counterparts.

"The small number of TB cases in this study prevented us from examining the age-gradient of smoking-TB association at a finer age scale, and more studies are needed to confirm these findings," Lin said. "Because the baseline risk for active TB is higher in the elderly in many countries, a smaller but still elevated relative risk in this population may yet translate to a greater number of cases of active TB, and our findings should not be interpreted to mean that smoking poses a lower risk in the older population."

Furthermore, they found that while the prevalence of active TB is known to be greater among men, when they controlled for smoking, drinking and related social behaviours, those gender differences disappeared, raising the possibility that "smoking, not biological differences, may be the underlying cause of the sex difference in TB."

How smoking increases TB risk
Smoking may increase the risk of developing active TB through different biological mechanisms, including the impaired clearance of secretions on the tracheobronchial mucosal surface, reduced phagocytotic function of pulmonary alveolar macrophages, decreased production of tumour necrosis factor in pulmonary macrophages, and increased iron overload in pulmonary macrophages. The pulmonary macrophages are the body's primary defence mechanism to contain M. tuberculosis.

"To our knowledge this is the first cohort study from a general population that provides evidence on the positive association between tobacco smoking and active TB. Based on results from ours and other studies, policy makers and public health personnel should consider addressing tobacco cessation as part of tuberculosis control.

From the perspective of prevention, the target of smoking cessation should aim beyond TB patients to reach high-risk populations who are most likely to benefit from cessation," said Dr. Lin. "Further studies are needed on smoking and TB in different countries and ethnic groups, as well as randomised trials of smoking cessation that look at incident TB as one of the outcomes." – (EurekAlert, August 2009)

Read more:
Smokers' tongues fail taste test
Smokeless tobacco still dangerous


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