Thursday, April 10, 2014

Week 3: Mortality Rates, Causes of Death and Burden of Disease

Life expectancy, mortality rates (including distribution of deaths), causes of death and burden of disease can provide great insight into a country and what it is like to live there for the general population.  The data can help us start to answer several questions such as: what is the quality of life for the majority of residents?  What sort of challenges do people living there face?  Is there easy access to clean water and healthy food?  Is there a well-functioning health system?  Where is the country geographically situated (i.e. is it situated in the northern hemisphere or is it tropical or subtropical and therefore vulnerable to tropical diseases)?  Is it a safe place to live or is there a high risk of violence?  Are there issues regarding hygiene and sanitation? Is there safe and solid infrastructure in place for the transportation of people and goods into, out of and within country?

For starters, developed countries have relatively low mortality rates and high life expectancies.  The biggest health concerns in these nations are non-communicable diseases like cancer, heart disease, stroke and diabetes.  Essentially, most people in rich countries are no longer becoming disabled or dying prematurely of diseases that can be transmitted or conditions that are easily avoidable with modern medicines and procedures.  They have well-functioning health systems and programs in place to protect them from those.  Instead, they are living well into their later years and are more likely to die or suffer from disabilities due to diseases related to lifestyle, aging and other risk factors that are more difficult to manage. 

Low income countries on the other hand, generally have lower life expectancies and higher mortality rates.  Although non-communicable diseases are a growing problem, what really sets poor countries apart from their wealthier counterparts are the high numbers of death and disability from communicable diseases as well as those related to pregnancy, childbirth, diarrhoeal diseases and malnutrition.  These conditions would be easily preventable if only for easy access to proper health and education services.

Middle income countries find themselves somewhere... well, in the middle.  Some have relatively well-functioning healthcare services and therefore have life expectancies that are close to being on par with those in wealthy nations (like Cuba at approximately 78 years), others are not quite there yet (like India at around 67 years) (Index Mundi 2012).  Most middle income countries are still battling communicable diseases and elevated maternal and neonatal mortality (like low income countries), but they are also facing high rates of non-communicable diseases (like high income countries).

Let's take a look at some of the data from Zimbabwe that we examined in class:

Now, let's assume that I know nothing about Zimbabwe other than this data that I have been given.  Taking into consideration what I know about the typical patterns of disease and mortality in countries at different stages of development, I can begin to infer a lot about this country based solely on this information.  The country appears to have a low life expectancy and communicable diseases make up the overwhelming majority of causes of disability adjusted life years, with HIV/AIDS being at the top of the list.  This points to a low income, tropical or subtropical country.  The large presence of diarrhoeal diseases speaks to insufficient hygiene and sanitation and poor access to clean water.  The prevalence of birth asphyxia, preterm births and other neonatal problems tell me that the health system is severely lacking in terms of antenatal, maternal and postnatal services.  Looking at the number of homicidal injuries, I would consider the country to be a relatively dangerous place to live in terms of personal safety.  I would presume that the quality of life for most people in this country is relatively poor.

Now because I do know quite a bit about Zimbabwe, in part because I have family that lives there, I know that my conclusions are fairly, if not entirely accurate.  So, this got me thinking...  What about my home country?  Would the statistics taken from Canada reflect my personal experiences of living there? 

Non-communicable diseases are the biggest factor contributing to morbidity and mortality in Canada.  The number of people that I know living there who have diabetes, high blood pressure, high cholesterol or have suffered a stroke is more than I can count.  That being said, one of the problems people worry about most is actually our weather.  

For roughly six months every year (sometimes longer), ice and snow blanket our roads interfering with our driving and cover the ground and walkways making it difficult for us to walk without falling.  

Ice forms atop bodies of water that people often decide to cross or fish on, sometimes without the layer being thick enough to hold their weight.  

These frozen forms of precipitation also weigh down the branches of trees that eventually snap and fall or begin to melt before freezing again in the form of daggers, dangling precariously from rooftop awnings.   

Snow and ice are both beautiful and scary to Canadians.  But, is that much fear really warranted when we look at the actual facts?  I mean we have developed snow tires, we have a veritable army of snow plows, we salt every square inch of cement or asphalt we see and our warning systems keep us updated every minute of our lives.  In school, university and  social programs, we even teach our children how to save someone that has fallen through the ice.  Are we getting ourselves all worked up over something that isn't much of a problem anymore with all of the systems that we have in place?  The only way to really know is to look at the data.  

The pie charts that we looked at in class did not differentiate between intentional and accidental injuries, lumping everything from suicides and burns together.  Therefore to get my answer, I knew I'd have to find more specific data.  This is what I found to start off with from the Statistics Canada website:

Leading causes of death, by sex
(Both sexes)
Both sexes
rank number %
Total, all causes of death 242,074 100
Malignant neoplasms (cancer) 1 72,476 29.9
Diseases of heart (heart disease) 2 47,627 19.7
Cerebrovascular diseases (stroke) 3 13,283 5.5
Chronic lower respiratory diseases 4 11,184 4.6
Accidents (unintentional injuries) 5 10,716 4.4
Diabetes mellitus (diabetes) 6 7,194 3
Alzheimer's disease 7 6,356 2.6
Influenza and pneumonia 8 5,767 2.4
Intentional self-harm (suicide) 9 3,728 1.5
Nephritis, nephrotic syndrome and nephrosis (kidney disease) 10 3,294 1.4
Notes: Causes of death are coded to the 10th revision of the World Health Organization's International Statistical Classification of Diseases and Related Health Problems (ICD-10).
Sources: Statistics Canada, CANSIM table 102-0561.
Last modified: 2014-01-28.
(Statistics Canada 2014a)

According to this chart, unintentional injuries (therefore excluding injuries as a result of homicide or suicide) are the fifth leading cause of death among Canadians.  In fact, unintentional injuries are the leading cause of death and hospitalization for people between the ages of 1 and 34 (looking at data from 2005) (Public Health Agency of Canada 2005).  But how many of these deaths might be related to weather increasing the risks of car accidents, slips and falls and falling through the ice?

Figure 1
Proportion of unintentional injury deaths by cause in Canada excluding Quebec, 2001–2007

Figure 1 Proportion of unintentional injury deaths by cause in Canada excluding Quebec, 2001–2007

(Chen et al. 2013, p. 98)

At first glance, the figures from 2001 to 2007 appear to corroborate the widespread concerns over the dangers posed by weather conditions.  Falls and motor vehicle accidents are two of the biggest categories of unintentional injuries, but reading further into the results revealed a bit of a contradiction.  Only falls were found to occur more often during the winter, with deaths from motor vehicle accidents actually happening more frequently in the summer (Chen et al. 2013).  Of course that is not to say that no deadly car accidents happen in the winter because of poor weather conditions, but I have to say that I did not see that particular result coming.  I thought for sure that with black ice and all of the whiteouts that we have, more fatal car accidents would take place in the winter.  One reason that the authors put forth to explain this particular finding was that people were more likely to drive for longer periods of time in the summer, going on vacation, etc (Chen et al. 2013).  But, the more that I think about it, the more that I believe that it simply boils down to the fact that Canadians are more cautious when driving in the winter because we are so concerned about the conditions.  So we take all of those precautions, we drive slower, we get winter tires, we try to keep our trips short and we wait until the weather improves and the snow plows have cleared the roads before we travel anywhere.  Canadians probably have a false sense of security driving in the summertime because the conditions are so much better, so we take more risks.

As for drownings, they aren't all that common compared to other injuries, but the majority of them do occur in the summer (Chen et al. 2013).  This makes sense because pools are open, bodies of water are not frozen or icy cold so more people can go swimming.  With that in mind, should we not be more mindful of teaching children how to swim in addition to how to save someone who's fallen through the ice?  Yet swimming and water safety are not topics regucovered in primary or secondary schools in Canada.

Falls were the largest single contributor to deaths as a result of unintentional injury and they were found to occur most often in November and December (late fall, early winter).  The authors stated that one possible explanation for this is the fact that people decorate their houses for the holidays around that time, climbing on ladders, walking on their roofs, etc (Chen et al. 2013).  Another likely reason is the number of falls among the elderly slipping on suddenly icy walkways and fracturing their fragile bones, from which they may not recover.  At any rate, weather was found to be a factor (finally).

Having had my first motor vehicle injury hypothesis roundly disproven, I wanted to examine if there was any real truth to another belief that I have held largely as a result of anecdotal evidence.  My mother used to always say that she held her breath from the time her brother turned 16 until the time he reached 25, because so many young men die in that period as a result of unintentional accidents (especially since that is when they start to drive and seem to partake in riskier behavior).  So I decided to start by comparing the figures for men to those for women.

Leading causes of death, by sex
rank number %
Total, all causes of death 121,042 100
Malignant neoplasms (cancer) 1 37,916 31.3
Diseases of heart (heart disease) 2 24,987 20.6
Accidents (unintentional injuries) 3 6,243 5.2
Chronic lower respiratory diseases 4 5,551 4.6
Cerebrovascular diseases (stroke) 5 5,486 4.5
Diabetes mellitus (diabetes) 6 3,825 3.2
Intentional self-harm (suicide) 7 2,781 2.3
Influenza and pneumonia 8 2,616 2.2
Alzheimer's disease 9 1,961 1.6
Nephritis, nephrotic syndrome and nephrosis (kidney disease) 11 1,641 1.4
Notes: Causes of death are coded to the 10th revision of the World Health Organization's International Statistical Classification of Diseases and Related Health Problems (ICD-10).
Sources: Statistics Canada, CANSIM table 102-0561.
Last modified: 2014-01-28
 (Statistics Canada 2014c)

Leading causes of death, by sex
rank number %
Total, all causes of death 121,032 100
Malignant neoplasms (cancer) 1 34,560 28.6
Diseases of heart (heart disease) 2 22,640 18.7
Cerebrovascular diseases (stroke) 3 7,797 6.4
Chronic lower respiratory diseases 4 5,633 4.7
Accidents (unintentional injuries) 5 4,473 3.7
Alzheimer's disease 6 4,395 3.6
Diabetes mellitus (diabetes) 7 3,369 2.8
Influenza and pneumonia 8 3,151 2.6
Nephritis, nephrotic syndrome and nephrosis (kidney disease) 9 1,653 1.4
Sepsis 10 1,332 1.1
Notes: Causes of death are coded to the 10th revision of the World Health Organization's International Statistical Classification of Diseases and Related Health Problems (ICD-10).
Sources: Statistics Canada, CANSIM table 102-0561.
Last modified: 2014-01-28.
(Statistics Canada 2014b)

Sure enough, unintentional injuries are ranked as the third cause of death for men, even ahead of stroke, but only the fifth cause of death for women (Statistics Canada 2014c).  The data from 2001 to 2007 shows that deaths due to traffic accidents in particular were higher among men than women and greater in young people (Chen et al. 2013).  Therefore, it would seem that my mother was right to worry, young men are at an increased risk of dying of unintentional injuries, especially from car accidents.

In the end, mortality rates, causes of death and burden of disease can indeed provide valuable insight into a country, the problems it faces and the lifestyle of most people who live there.  But, as I have learned, the facts do not always match up with our assumptions and can be misinterpreted (even by residents of that same country).  Therefore, it's important to get as much information as possible before coming to a conclusion.


Chen Y, Mo F, Yi QL, Jiang Y & Mao Y 2013, 'Unintentional injury mortality and external causes in Canada from 2001 to 2007', Chronic Diseases and Injuries in Canada, vol. 33, no.2, pp. 95-102.  Available from: <>.  [8 April 2014].  

Index Mundi 2012, Life expectancy at birth by country.   Available from: <>. [8 April 2014].

Public Health Agency of Canada 2005, Leading Causes of Death and Hospitalization in Canada.  Available from: <>.[8 April 2014].

Statistics Canada 2014a, Leading causes of death, by sex (Both sexes).  Available from: <>.[8 April 2014].

Statistics Canada 2014b, Leading causes of death, by sex (Females).  Available from: <>.[8 April 2014]. 

Statistics Canada 2014c, Leading causes of death, by sex (Males).  Available from: <>.[8 April 2014]. 

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