Risk Factors and Actual Causes of Death

The leading causes of death tell us the importance of chronic diseases (also known as “killer diseases”) in our society and the evolution of a chronic diseases epidemic. I have also made a case about the potential preventability for most of these diseases. However, the story is not complete. What actually causes these diseases and how come they are so highly preventable?

Before going to answer this important question, I would like to provide a brief explanation of how we should all look at diseases. Diseases are caused by risk factors (also known as causes or determinants), which are variables that if present can lead to an increased chance of acquiring a particular disease. Risk factors, in themselves, can be subdivided into those that can be modified (for example, our diet and physical activity) and those that cannot (age and gender for example). These risk factors then are the root causes of most of the “killer diseases”.

As mentioned above, the causes of the main chronic disease epidemics are well established and well known. In fact, a seminal 1993 study by McGinnis & Foege which was updated in 2004 by Mokdad, A. H. et al. entitled Actual Causes of Death in the United States, 2000 presents what these causes or risk factors are in the following order:

1. Tobacco
2. Poor diet and physical inactivity
3. Alcohol Consumption
4. Microbial Agents
5. Toxic Agents
6. Motor vehicle crashes
7. Firearms
8. Sexual behaviours
9. Illicit drug uses

More specifically, the leading causes of death in 2000 were tobacco (435 000 deaths; 18.1% of total US deaths), poor diet and physical inactivity (365 000 deaths; 15.2%), and alcohol consumption (85 000 deaths; 3.5%). Other actual causes of death were microbial agents (75 000), toxic agents (55 000), motor vehicle crashes (43 000), incidents involving firearms (29 000), sexual behaviors (20 000), and illicit use of drugs (17 000).

The most important modifiable risk factors therefore are:

•       tobacco use.

•       unhealthy diet and excessive energy intake;

•       physical inactivity;

These account for approximately 33.3% of all deaths by themselves. It is important to note that given the continuing trends, poor diet and physical inactivity may soon overtake tobacco as the leading cause of death.

These 3 risk factors are facets of our own lifestyles (sleep and stress being the other ones) and hence the use of the term lifestyle medicine which some of us advocate and practice. Preventive medicine, the title of this blog, is a broader term that includes lifestyle medicine but goes beyond that in that it deals with all aspects of prevention (including screening for diseases, behavioural counselling, immunizations and preventive therapies).

Another way of looking at risk factors is to divide them into proximal, intermediate or distal risk factors depending on how far away they are in the causal chain of the disease. For example, the distal risk factors of diet, exercise and smoking are expressed through the intermediate or proximal risk factors of raised blood pressure, raised glucose levels, abnormal blood lipids (particularly low density lipoprotein – LDL – cholesterol), and overweight (BMI ≥ 25) and obesity (BMI ≥ 30).

The World Health Organization has released a 2005 report entitled Preventing chronic diseases: a vital investment: WHO global report which explains and diagrams these risk factors.

Another great diagram of the interrelationship of these risk factors can be found on page 54 in the report entitled: A Report Prepared for Chronic Disease in Ontario and Canada: Determinants, Risk Factors and Prevention Priorities.

The key take home point here is the following: modifiable risk factors are the root causes of the “killer diseases”. More importantly, we are in control of these modifiable risk factors and hence we can prevent most of these chronic diseases.

With this in mind we can continue to ask important questions of our own doctors. If in fact these risk factors are the true root causes of death, wouldn’t it make sense for your doctor to spend most of their time (if not all of it) assessing your risk factors, creating a risk factor profile for each of you so that a prevention plan could be put in place to deal with the risk factors and avoid disease? The truth of the matter is that due to a variety of reasons, this is not happening and most health care providers deal with symptoms of disease and never address the risk factors, in fact creating a stop-gap solution to your own health care issues. I will address this important issue in a later post.