Chapter 3: The Chief Public Health Officer's report on the state of public health in Canada 2008 – Causes of death

Our Population, Our Health and the Distribution of Our Health

Causes of death

If recent trends continue, six out of ten Canadian deaths in 2008 will be attributable to either circulatory diseases (largely heart attack, heart failure or stroke) or cancers. While the absolute numbers are high, the rate at which people are dying prematurely of these diseases is lower today than in the past considering the increase in population size.¹⁶²

Over the last half century, taking into account changes in the age distribution of the population from year to year (by age-standardization), the overall mortality rate for all causes combined has declined steadily (see Figure 3.9).¹⁶³ In other words, Canadians are living longer. The overall age-standardized mortality rate for all ages and sexes combined has declined from 1,219 deaths per 100,000 population in 1950 to 572 per 100,000 in 2004.^{164, 165, 166}

Much of the decline in overall mortality rates is attributable to the more than 70% decline in death rates related to circulatory diseases – most notably ischemic heart disease and cerebrovascular disease (including stroke). Age-adjusted mortality rates across all cancer sites have not changed significantly since the 1950s.^{164, 165, 166}

Figure 3.9 Age-standardized mortality rates for select causes, Canada, 1950-2004

ASMR – Age-standardized mortality rate.
Source: Public Health Agency of Canada using Health Canada’s Data
Analysis and Information System (DAIS), Statistics Canada, CANSIM Tables.

Figure 3.10 Mortality by select causes and age groups, Canada, 2004

Source: Public Health Agency of Canada using Statistics Canada, CANSIM Tables.

Patterns, rates and causes of mortality vary within the population according to different factors such as age, sex and income.¹⁶⁷ The pattern of mortality by age group is presented in Figure 3.10 and shows both the different causes of death and their proportion of all deaths for Canadians of different ages. For example, although deaths due to injuries and poisonings represent a substantial proportion of all deaths in children and youth aged 0 to 19 years, in relation to the entire population the actual number of those deaths is small given that deaths in that age group account for less than 2% of all deaths.¹⁶⁸ In contrast, beginning around age 45, the majority of deaths are due to circulatory diseases and cancers and represent the majority of all deaths in Canada.¹⁶⁹ As would be expected, most deaths (for all causes) occur in the older age groups (78%), regardless of their relative importance in younger age groups.

Mortality rates also vary by neighbourhood income.¹⁴⁴ Death rates due to ischemic heart disease are decreasing for men (as shown in Figure 3.11), and the gap between those living in the highest- and lowest-income neighbourhoods is narrowing.¹⁴⁴ Most of this ‘gap narrowing’, however, occurred between 1971 and 1991, with almost no further narrowing in the subsequent decade.

In other cases the opposite is true. Death rates for lung cancer in women are increasing for all income levels and the mortality gap between highest- and lowest-income neighbourhoods is widening (see Figure 3.12).¹⁴⁴ Much of this pattern is a reflection of past smoking practices among Canadian women.^{170, 171, 172}

Figure 3.11 Age-standardized mortality rates for ischemic heart disease by neighbourhood income, male, urban Canada, 1971-2001

ASMR – Age-standardized mortality rate.
Q – population divided into fifths based on the percentage of the
population in their neighbourhood below the low-income cut-offs.
Source: Wilkins et al. (2007), Statistics Canada.

Figure 3.12 Age-standardized mortality rates for lung cancer by neighbourhood income, female, urban Canada, 1971-2001

ASMR – Age-standardized mortality rate.
Q – population divided into fifths based on the percentage of the
population in their neighbourhood below the low-income cut-offs.
Source: Wilkins et al. (2007), Statistics Canada.

Causes of premature death

While the number of deaths due to a particular disease is important to understanding the health of the Canadian population, so too is the age at which these deaths occurred. For example, if a Canadian dies of cancer at age 45, he or she has potentially lost 30 years of life (conservatively assuming a life expectancy of 75 years at birth, as is commonly done in these calculations). Measuring the number of potential years of life lost (PYLL) to premature death provides a better sense of the impact a given disease or condition has on the health of the population.

In Canada, the overall PYLL rate has been decreasing over time. However, cancers, circulatory diseases, injuries (both unintentional and intentional) and chronic respiratory disease continue to be the most significant early killers of Canadians. In 2001, these four causes accounted for more than 70% of the total 5,102 PYLLs per 100,000 population in Canada for all causes combined. In general, infectious diseases are not responsible for large numbers of premature deaths in Canada with the greatest contributor, HIV, adding only 46 PYLLs per 100,000 population in 2001 – less than 1% of the total years of life lost prematurely that year.¹¹⁶

Research indicates that where you live can have an impact on years of life lost to early death. Canadians living in more northern regions have a PYLL rate higher than the national average (e.g. the PYLL rate for residents of Nunavut is 2.5 times higher than average). This is due mainly to unintentional injuries, suicides and self-inflicted injuries. Those in the central and west coast areas of the country have PYLL rates lower than the average.¹¹⁶

There is also a PYLL difference between low- and high-income neighbourhoods. In 2001, more total years were lost to premature death in lower-income urban neighbourhoods than in the 20% of neighbourhoods with the highest incomes. If the age- and sex-specific mortality rates in the highest-income quintile had applied to the entire population, the total PYLL for all urban neighbourhoods would have been reduced by approximately 20% – the equivalent of eliminating all premature deaths due to injuries in those neighbourhoods.^{144, 173}