A group of researchers from Harvard, University of Auckland in NZ, University of Queensland in Australia, and something called the International Obesity Task Force in London have found that obesity and cholesterol levels peak in middle income countries and decline with higher incomes.
Cardiovascular diseases and their nutritional risk factors—including overweight and obesity, elevated blood pressure, and cholesterol—are among the leading causes of global mortality and morbidity, and have been predicted to rise with economic development.
Methods and Findings
We examined age-standardized mean population levels of body mass index (BMI), systolic blood pressure, and total cholesterol in relation to national income, food share of household expenditure, and urbanization in a cross-country analysis. Data were from a total of over 100 countries and were obtained from systematic reviews of published literature, and from national and international health agencies.
BMI and cholesterol increased rapidly in relation to national income, then flattened, and eventually declined. BMI increased most rapidly until an income of about I$5,000 (international dollars) and peaked at about I$12,500 for females and I$17,000 for males. Cholesterol's point of inflection and peak were at higher income levels than those of BMI (about I$8,000 and I$18,000, respectively). There was an inverse relationship between BMI/cholesterol and the food share of household expenditure, and a positive relationship with proportion of population in urban areas. Mean population blood pressure was not correlated or only weakly correlated with the economic factors considered, or with cholesterol and BMI.
When considered together with evidence on shifts in income–risk relationships within developed countries, the results indicate that cardiovascular disease risks are expected to systematically shift to low-income and middle-income countries and, together with the persistent burden of infectious diseases, further increase global health inequalities. Preventing obesity should be a priority from early stages of economic development, accompanied by population-level and personal interventions for blood pressure and cholesterol.
I have to quibble with their comment about "persistent burden of infectious diseaes". I doubt that middle income countries labor under as much infectious disease burden as lower income countries. As incomes rise and obesity and cholesterol become problems disease burdens probably fall for a number of reasons including wider spread vaccination, better housing which reduces exposure to disease and to weather, reduced malnutrition of types that suppress immune response, and cleaner water.
In the longer run I expect the infectious disease burden to drop even in many lower income countries as vaccines get developed which are cheaper and easier to deliver (e.g. geneticaly engineered into foods), advances in nanotechnology make water purification cheap, and other advances made in the industrialized countries get delivered cheaply to the basketcase countries of the world.
I think they are on firmer ground in claiming that there are inflection points where the health consequences of rising affluence on cardiovascular disease reach a peak and then reverse. People in the most developed countries are more likely to get screened for cardiovascular risk factors and to take statin drugs to lower cholesterol and drugs to lower blood pressure. They also have more income to spend on fruits and vegetables and to purchase other foods that lower risks (e.g. fish).
An accompanying essay by Thomas E. Novotny of UCSF entitled Why We Need to Rethink the Diseases of Affluence makes an important point about environmental engineering.
As populations assume more of an urban lifestyle, they should not be limited in their choices for healthy foods, suffer from lack of safe water, or lose opportunities for physical activity. These problems can be reduced through good urban planning, better food policies, improved environmental engineering, and better attention to healthy lifestyle practices in our growing cities. Screening for hypertension, hypercholesterolemia, and nicotine addiction need to become a part of good clinical practices in low- and middle-income countries. Of course, screening for these risks should then also be accompanied by better availability of low-priced secondary prevention therapies such as generic versions of anti-hypertensives, statins, and nicotine replacement therapies.
The amount of exercise that people get in more urbanized and suburban environments could be increased if areas were set aside for public parks, streets were designed to be more pedestrian and bicycle friendly, and zoning put stores and offices within walking distances of homes.
Also, note Novotny's reference to nicotine replacement therapies. This touches on a larger subject: It is my impression that the United States has a much more anti-smoking regulatory environment than less developed countries and even than the bulk of the most industrialized countries. Some of the other Western industrialized countries are trending toward reducing smoke exposure in work places and discouraging smoking. That lowers cardiovascular risk relative to lower and middle income countries which generally have fewer limits on cigarette smoking, sales, and advertising and fewer public health warnings against smoking.
Food fortification is also probably making a difference. For example, the addition of folic acid to grain-based foods in the United States is lowering average blood homocysteine and that is reducing cardiovascular diseasa. The motivation behind the folic acid fortification was to lower spina bifida birth defects. The cardiovascular disease reduction is a bonus. But fortification is cheap and could and should be implemented more widely in middle and lower income countries. Africa would benefit especially.
In the medium run I expect the cost of cardiovascular disease reduction to fall to levels that cause cardiovascular risk reduction practices to spread to medium and lower income groups and countries. Genetic engineering of foods will improve diets. For example, genetic engineering will increase omega 3 fatty acid levels in grains and livestock while simultaneously reducing the level of fats that most increase cardiovascular risks. Another possibility is the genetic engineering of food crops to raise levels of a compound called beta sitosterol which is now used in special cholesterol lowering margarines. Also, cheaper, safer, and easier ways to control appetite and reduce nicotine cravings will be found.
In the long run I expect to see genetic engineering of liver cells to make them control blood lipid and cholesterol levels to assure optimal blood for cardiovascular health. Also, stem cell therapies and other gene therapies will allow repair of all atherosclerotic plaque damage and heart muscle damage.
|Share |||Randall Parker, 2005 June 29 12:34 PM Trends Health|