19 September 2011

Noncommunicable diseases

This week the United Nations will hold a high level meeting that focuses on the prevention and treatment of noncommunicable diseases (see, UN: http://www.un.org/en/ga/ncdmeeting2011/).  The major diseases considered here are cardiovascular disease, diabetes, cancer, and chronic lung disease.  Many of these diseases have communicable risk factors; fore example, Helicobacter pylori has been associated with certain gastric cancers, human papillomavirus (HPV) is responsible for almost all cervical cancers, and hepatitis is a risk factor for liver cancer.  Nevertheless, the conditions themselves - cancer in the case of these examples - are noncommunicable.  As in the literature, chronic and noncommunicable are used somewhat interchangeably here.  For most of these diseases there are risk factors that are tied to lifestyle rather than communicable diseases.

Noncommunicable diseases (NCD) have been considered diseases of affluence; however, the data suggest that this is not true.  Narayan et al. [2011] cites that these chronic diseases cause 60% of deaths with 80% of them in low- or middle-income countries.  Furthermore, in these low- and middle-income countries there is a disproportionate disease burden on younger people.  This means that in poorer countries people are dying of these diseases earlier, as opposed to near their life-expectancy, and during their economically most productive age.  It may be the case that developing countries have underreported NCD morbidity and mortality.  In the case of cancer, more than half of cancer deaths occur in developing countries [Morrish, 2011].  The cancers that are prevalent in the developing world are gastric cancers, cervical cancer, and others that the developed world has greatly decreased through education, early detection, and prevention (especially in the case of vaccines).  One NCD that has not been included, but was suggested during a discussion on NCDs with the Duke Global Health Institute (DGHI), is mental health.

Globalization has increased the risk factors for these diseases; namely, tobacco, environmental pollution, popularity of high-salt foods, and sedentary lifestyle [Narayan, 2011].  It was also observed in the DGHI discussion that in contrast to communicable diseases, where the cause is an infectious agent, the cause of NDCs are more varied and have a large lifestyle component.  This introduces the possibility that companies that promulgate these products (e.g., tobacco and salty foods) can evade researchers in very different ways.

The behavior of politicians came up in the DGHI discussion.  Politicians have historically responded to disease with treatment as opposed to preventative measures.  For NCDs, prevention could take years to almost a lifetime to show effectiveness; however, treatment will show efficacy, on average, much faster.  It is in politicians best interest to choose treatment options over prevention.

The Lancet NCD Action Group and the NCD Alliance have identified five priorities in combatting noncommunicable disease.  These are the result of determining the greatest causes of the most prevalent conditions.  They are tobacco control, salt reduction, improved diet and physical activity, reduction of hazardous alcohol intake, and the availability of essential drugs and technologies [Beaglehole et al., 2011].  Stuckler et al. [2011] claim that the millennium development goals do not include noncommunicable diseases, which the do not; however, they do include topics that could (and should) address many of the risk factors.  Specifically, end poverty, child health, and maternal health.

Urbanization in the developing world has contributed to the popularity of food with low nutritional value because it can be shipped and stored easily.  Corporations also aggressively market these products to new audiences [Stuckler et al., 2011].

Beaglehole et al. [2011] compiled the several recommendations and their cost for implementation.  Based on those interventions that had estimated impact in terms of premature deaths averted, we can rank three of these interventions by cost benefit.  The most efficient intervention is reduction in salt, reduction in tobacco use, and increased availability of drugs for NCDs.

While advertisement of the number of lives saved if a convenient way to quantify the threat of NCDs, it does not tell us what proportion of NCDs could not have been prevented regardless of setting (low-, middle-, or high-income counties).  It would be better if these reports began to use the disability-adjusted life-year (DALY).

Engineers have an important role in the reduction of NCDs.  The World Health Organization compiled the top 10 risk factors (not causes) for death by income level [cited in Narayan, 2011].  In low-income countries there are two risk factors that require engineering interventions:
4. unsafe water and poor sanitation and hygiene,
6. indoor smoke from solid fuels;
in middle-income countries:
9. indoor smoke from solid fuels,
10. urban outdoor air pollution;
and in high-income countries:
8. urban outdoor air pollution,
10. occupational risks.
Unsafe drinking water and poor sanitation have implications for infectious disease, but they can also be tied to toxic chemicals that can cause cancers and reproductive problems.  Indoor smoke can cause acute and chronic lung problems including cancers, emphysema, or chronic obstructive pulmonary disease.  Urban outdoor air pollution carries similar risks to indoor air pollution, but is usually or a different composition.  Ozone, from automobiles for example, has been linked to asthma and respiratory problems in the very young and elderly.  Finally, occupational risks cover a broad spectrum of hazards, but they can all need engineering solutions.

There is also an opportunity for education.  In the developing world, education has already shown benefits for maternal health [Boyle, 2006].  Education, combined with the development and availability of a cost-effective solution, can reduce major risk-factors.


References:

Beaglehole, R., et al. (2011), Priority actions for the non-communicable disease crisis, Lancet, 377(9775), 1438-1447.

Boyle, M. H., Y. Racine, K. Georgiades, D. Snelling, S. Hong, W. Omariba, P. Hurley, and P. Rao-Melacini (2006), The influence of economic development level, household wealth and maternal education on child health in the developing world, Social Science & Medicine, 63(8), 2242-2254.

Morrish, N. (2011), The United Nations of Cancer, Livestrong Qtrly., 1(7), 64-65.

Narayan, K. M. V., M. K. Ali, and J. P. Koplan (2010), Global Noncommunicable Diseases - Where Worlds Meet, N. Engl. J. Med., 363(13), 1196-1198.

Stuckler, D., S. Basu, and M. McKee (2011), Commentary: UN high level meeting on non-communicable diseases: an opportunity for whom?, BMJ, 343.

1 comment:

  1. Interesting article on lifestyle causes of cancer: http://www.bbc.co.uk/news/health-16031149

    ReplyDelete