Monday, March 12, 2012

Drinking for a Healthy Heart: A heart helper with an expensive toll?


For the past few years, cardiovascular disease (CVD) has been the lead contender for causes of death.  According to the World Health Organization (more statistics) CVD is responsible for close to 30% of total global deaths, and is affecting everyone - it has no geographic, gender, or socio-economic boundaries. The extent of CVD’s affect on population is staggering , causing more than 12 million premature deaths per year. Historically it was a disease of the developed world, but currently 80% of all CVD deaths take place in developing, low, and middle-income countries. 
The coronary artery supplies blood and oxygen to the heart muscle. When a clot forms around a rupture, blood flow is blocked, and a heart attack is induced.

Cardiovascular disease is any ailment that involves the heart, arteries, or veins. To understand how we can prevent this disease requires some basic understanding of human physiology. The following information is most pertinent to atherosclerosis, the most common form of CVD, but most cardiovascular ailments are very much related in mechanism, causes, and treatments.  

Atherosclerosis is the process by which your arteries become hardened. It results in reduced or diminished blood flow through the arteries. The inflammatory response that takes place in artery walls begins with a build up of low-density lipoprotein (LDL cholesterol) molecules. In the animation below, LDL cholesterol (yellow blobs) burrow into artery walls. Your body responds by sending inflammatory cells, both white blood cells and monocytes (represented by purple blobs) that migrate into the wall.  The monocytes then transform into macrophages, which consume LDL cholesterol. The result: formation of a “fatty streak” in the wall of the artery.  


As time passes and more LDL cholesterol builds up, the fatty streaks turn into a hard plaque. As your body tries to heal itself, a smooth cap is formed around the plaque, which may eventually rupture and form a clot (see animation below, or here for more detail).  


So, what can we do? There are a few modifiable risk factors that can significantly reduce the probability  of development of atherosclerosis, and at the same time contribute to improved over-all health. These include simply exercising; quitting smoking, and diet modification. By walking thirty minutes a day you can reduce your risk of developing CVD by up to 25%, and for all you cigarette smokers: smoking can increase your risk by 200% ! Diet modifications include increased intake of fish - the omega-3 fatty acids that many cold-water fish contain can reduce inflammation…and moderate alcohol consumption! “Moderate” being the key word here.

A variety of studies have shown that drinking up to one drink (15 grams of alcohol per day) for women, and up to two drinks (30 grams of alcohol) per day for men, is actually good for our health! Research has shown that drinking alcohol in moderation can actually decrease the likelihood of developing CVD by up to 25% in comparison to those who abstain.

“How?” Well there are a few different ways alcohol can work on the body to reduce your risks of CVD:  

·      Alcohol increases your HDL cholesterol. High density cholesterol (HDL) act as cholesterol scavengers. They pick up excess cholesterol in your blood and take it back to the liver, where it is broken down.
·      Alcohol lowers blood pressure.
·      Alcohol increases levels of fibrinogen. Fibrinogen is a blood clotter, or coagulant.
·      Alcohol increases thrombosis. Thrombosis is the formation of a clot.
·      Alcohol increases fibrinolysis. Fibrinolysis is a process by which blood clots are broken down.

What type of alcohol? You pick your poison. Studies have shown that it is purely the impact of alcohol that provides the health benefit, not the type of alcoholic beverage. Something to keep in mind when deciding your means of preventing CVD is the alcohol content of different beverages. If the cut-off between moderate and increased alcohol consumption is 15 or 30 grams for women and men, respectively, that would be less than one standard drink for women, or a little less than two standard drinks for men. A standard drink is either one 12 ounce can, glass, or bottle of beer (5% alcohol), one 5 ounce glass of wine (12% alcohol), or one 1.5 ounce shot of spirits (40% alcohol).

How is this related to population ecology?
There are a few different scales that the topic of cardiovascular disease can be looked at when thinking about population models. On a small scale: the ratio of HDL to LDL cholesterol is important to your risk for CVD. An optimum ratio of 3.5-to-1 for HDL to LDL has been cited by the American Heart Association to maintain a balance and have no build up of LDL in artery walls. This relationship could potentially be put into the model of predator and prey, where LDL is the prey, which is “consumed” by HDL, the predator.  In the case where HDL is absent, LDL grows exponentially. The threshold of this model is when the amount of LDL is too high, and a heart attack occurs.

On a larger scale, CVD is responsible for a huge portion of our death rate. What would happen to our population if we decreased the occurrence of CVD significantly? And do we really want that? This is a weighted question, but one to consider when looking at a factor with such a huge influence on the death rate of our population. According to the World Health Organization estimate, in 2008 30.5% of all deaths worldwide were caused by CVD. Drinking moderately can reduce your risk of CVD by up to 25%. Does this mean that if everyone in the world has one drink a day there is the potential to significantly decrease the amount of deaths caused by CVD?  Will this be counteracted by more alcohol related deaths?
Total adult (15+) per capita consumption, in litres of pure alcohol, 2005

This leads to the third element of population dynamics: alcohol’s role in social interactions within our species. Alcohol plays many different cultural roles in societies around the world. In the above graphic, the total recorded alcohol per capita consumption, in pure liters of alcohol is illustrated, based on the WHO Global Status Report on Alcohol. In the below graphic, we can see that alcohol attributable deaths as a percentage of total deaths.
Alcohol-attributable deaths as a percentage of total deaths, by WHO, 2004

What can we conclude by the comparison of geographical alcohol consumption and mortality? We can see that there are very few alcohol related deaths in countries with primarily Muslim populations, where alcohol is very much abstained from due to religious reasons. The highest proportion of alcohol-attributable mortality is in the Russian Federation and nearby countries. So what about the countries in the middle? There are a relatively low proportion of deaths in Western European countries, even in spite of the high level of alcohol consumption. This may be attributable to the drinking patterns, age structure, and beneficial impact of low-risk drinking on health concerns such as CVD!

The long term affects of alcohol range from possible health benefits for low levels of alcohol consumption, to severe detrimental causes in cases of chronic abuse of alcohol. There is a fine line between drinking in moderation, receiving these preventative affects on development of CVD, opposed to drinking in excess which can lead to CVD. Although there are strong benefits from drinking one to two drinks per day, the consumption of alcohol should not replace possibly safer, and more traditional methods such as exercise, good nutrition, and reduced tobacco use. Health benefits of moderate alcohol consumption do have very apparent benefits and are recommended, but some experts do suggest drinking with caution because moderate consumption may in turn lead to increase risk of alcohol abuse.

The preventative characteristics that alcohol exhibits could possibly reduce deaths caused by CVD, but how realistic is patient compliance when a doctor recommends only a small quantity of alcohol? 


For more information: 

BMJ-British Medical Journal (2011, February 22). Drinking alcohol in moderation protects against heart disease, meta-analysis finds. ScienceDaily. Retrieved March 11, 2012, from http://www.sciencedaily.com­ /releases/2011/02/110222192913.htm

Boone-Heinonen, Janne; Eenson, Kelly R.;Taber, Daniel R.; Gordon-Larsen, Penny. Walking for prevention of cardiovascular disease in men and women: a systematic review of observational studies. PMC 2010

Britton, Annie; McKee, Martin. Relation between alcohol and cardiovascular disease in Eastern Europe: explaining the paradox. Epidemiol Community Health 2000;54:328-332

Mitchell, Richard Sheppard; Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson (2007). Robbins Basic Pathology: With STUDENT CONSULT Online Access (8th ed.). Philadelphia: Saunders. pp. 345

P. E. Ronksley, S. E. Brien, B. J. Turner, K. J. Mukamal, W. A. Ghali. Association of alcohol consumption with selected cardiovascular disease outcomes: a systematic review and meta-analysis. BMJ, 2011; 342 (feb22 1): d671

2 comments:

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  2. The two blogs on heart disease complement each other well, and both clearly articulate the issues and their lines of thinking.

    This blog makes me happy because there are maps, and as a geography grad student (with a biology background) anything with maps makes me happy! I'm actually quite curious about the map of per capita alcohol consumption by country, in particular, the consumption of alcohol in sub-Saharan African countries and whether/how informal consumption (i.e. non-purchased) of alcohol was accounted for. That is, in some of the non-muslim parts of Africa I've been in, I've seen fairly high consumption of informally produced alcohol like palm wine and I'm wondering if that's been captured at all in this study. The high rate of alcohol consumption in Nigeria where palm wine is often celebrated in their literature and music makes me think that it may be included, but the low consumption everywhere else makes me wonder if it is.

    The map of alcohol-attributable deaths is also intriguing and I'm wondering what is included in alcohol-related deaths. I'm not sure if I follow or agree with the blogger's assessment of the pattern of alcohol consumption and alcohol-related deaths in Western European (high alcohol consumption but low levels of alcohol-related deaths), but maybe I'm not thinking this through clearly. It's an interesting pattern. However, by the reasoning of the rest of the blog, if moderate rates of alcohol conumption lead to lower deaths by heart disease then it follows that if this leading cause of death is reduced, the proportion of deaths caused by other mechanisms (including alcohol-related) might increase as a proportion of all deaths since the leading cause of death (heart disease) had been reduced in association with higher alcohol consumption. Therefore, there must be some other explanation for the reduction in alcohol-related deaths.

    The key thing that I appreciate about Lia's analysis of this issue is the overall consideration of "alcohol's role in social interactions within our species" and her careful consideration of the fact that alcohol has a complex relationship with human psychology, social behavior and culture. As I discussed in my comments on the other blog related to this topic, I fully concur with the question that she poses at the end, "how realistic is patient compliance when a doctor recommends only a small quantity of alcohol?" It's a good question at the end of a carefully nuanced discussion of cardiovascular disease, alcohol's potential reduction of these diseases and alcohols complex role in human culture. And the maps make me happy!

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