Health at a Glance
Deaths involving sepsis in Canada Health at a Glance
Deaths involving sepsis in Canada

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by Tanya Navaneelan, Sarah Alam, Paul A. Peters, and Owen Phillips

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Sepsis is a serious medical condition caused by an overwhelming immune response to an infection. The immune system sets off a series of reactions in the body including widespread inflammation, swelling and blood clotting.^{Note 1,Note 2} This results in impaired blood flow, which damages the body's organs by depriving them of nutrients and oxygen. If not treated quickly, sepsis can lead to multiple organ failure and death. It is estimated that 30% to 50% of people who develop sepsis die from it.^{Note 3,Note 4} Sepsis also has an economic burden by extending a patient's stay in the hospital^{Note 4} and significantly increasing the cost of treatment.^{Note 5}

Sepsis was the 12th leading cause of death in Canada in 2011, up from 15th place in 2000.^{Note 6,Note 7} Previous research shows that elderly people, males, and non-Caucasians have an increased risk of developing sepsis. People who develop sepsis often have other, pre-existing, conditions. The most common are human immunodeficiency virus (HIV), cancer, diabetes, cirrhosis, alcohol dependence, and bedsores.^{Note 8,Note 9}

This article provides the first Canadian estimates of sepsis-associated deaths; that is deaths where sepsis was either an underlying or contributing cause of death. Previous national estimates of sepsis deaths using administrative data sources have only included deaths where sepsis was the underlying cause of death.

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Data presented in this article come from the Canadian Vital Statistics – Deaths Database (CVS:D) and are analysed over time and by sex, age, and underlying cause of death. Data from the years 2000 to 2011 are used when discussing changes over time. Three years of data (2009, 2010 and 2011) are combined when discussing differences by age or underlying cause of death to reduce the random variation that can occur with small numbers.

One in 18 deaths in Canada involve sepsis

In 2011, there were 2,515 deaths where sepsis was reported as the underlying cause.^{Note 14} In addition, there were 10,985 deaths where sepsis was reported as a contributing cause^{Note 15}. This means that about one in 18 Canadian deaths involved sepsis that year (an age-standardized rate of 27.2 deaths per 100,000 people). This is similar to the level of sepsis-associated deaths found in England and the United States.^{Note 8,Note 16}

Sepsis as a contributing cause of death increased between 2000 and 2007

In the early 2000s, the rate of sepsis-associated death (both underlying and contributing) increased significantly (Chart 1). Between 2000 and 2004, the sepsis-associated death rate increased by 4.1% annually.^{Note 17,Note 18} The rise was even greater between 2004 and 2007 when there was an increase of 10.6% annually. However, there was no significant change between 2007 and 2011.

The increase in sepsis-associated deaths between 2000 and 2007 was mostly driven by increases in the recording of sepsis as a contributing cause of death. During this time period, the increase in the mortality rate when sepsis was a contributing cause of death (8.5%) was almost three times higher than when it was reported as the underlying cause (2.9%). While this increase in sepsis-associated mortality may reflect an actual increase in deaths involving sepsis, it may also be influenced by other factors including: changes in diagnosis methods and definitions, an increased awareness of sepsis by healthcare professionals, or changes in how deaths are classified.^{Note 19,Note 20}

Males have a higher risk of sepsis-associated death than females

Males had a significantly higher age-standardized rate of sepsis-associated deaths, at 31.7 deaths per 100,000, compared with females (23.8 deaths per 100,000) in 2011. This trend, of higher sepsis-associated deaths in males, was present in all years between 2000 and 2011 (Chart 2).

One possible reason why males are more likely to have sepsis involved in their death is that they may be more likely than females to develop sepsis in the first place.^{Note 16,Note 21} This difference may be related to hormonal and genetic differences between males and females or differences in the presence of other health conditions.^{Note 22,Note 23}

Between 2000 and 2007, sepsis-associated deaths increased significantly for males and females separately, with males having a higher rate of sepsis-associated deaths than females for all years (Chart 2). Since 2007, however, the gap between the sexes has started to close. Between 2007 and 2011, the sepsis-associated mortality rate among males decreased significantly, declining by 1.7% per year, while there was no significant change in the death rate for females during these years. As a result, the difference in the rates between males and females fell from a gap of 10.5 deaths per 100,000 in 2007, to 7.9 per 100,000 in 2011.

Sepsis-associated deaths increase with age

During the time period 2009–2011, the rate of sepsis-associated deaths increased by age among those 5 and older (Table 1). Deaths involving sepsis were highest among the oldest age group (85 and older) at 587.8 deaths per 100,000 and lowest between ages 5 and 19 (ranging from 0.7 to 0.8 deaths per 100,000). Infants under the age of 1 had a death rate of 33.0 deaths per 100,000, higher than the rates for those aged 1 to 59 years. The pattern of sepsis-associated deaths parallels that of deaths from all causes in Canada, where deaths are highest among the elderly and relatively high in those under the age of one.^{Note 24}

Sepsis contributed to deaths in every age group, from newborn babies to the elderly. Among those who died by age 30, sepsis contributed to a relatively similar percentage of mortality, varying between 4.0% and 6.2% of all deaths. (Table 1). However among children (those who died before the age of 15) sepsis contributed to a greater percentage of mortality, varying between 6.7% and 8.2% of all deaths. Adolescents and young adults (ages 15 to 29) were the least likely to have sepsis contribute to their deaths, with 2.0% to 3.3% of all deaths involving sepsis. While children were more likely to have sepsis contribute to their death than adults, older people experienced higher overall mortality than young people, resulting in higher rates of sepsis-associated mortality.

Sepsis contributes to more than one-half of all deaths from infectious disease

About 5.5% of all deaths in Canada during 2009–2011 were sepsis-associated.^{Note 15} Of the underlying causes of death that involved sepsis the most common was diseases of the skin and tissue under the skin (subcutaneous tissue) (61.8%), followed by infectious diseases (53.4%) (see Appendix A).^{Note 25,Note 26} Sepsis was also involved in over 10.0% of all deaths from diseases of the: digestive system, musculoskeletal system, and urinary system or genital organs.^{Note 27}

Deaths from infectious diseases provide a good example of how sepsis can be both an underlying and contributing cause of death. During 2009–2011, 53.4% of all infectious disease deaths involved sepsis (Table 2). In 82.2% of those deaths, sepsis was the underlying cause of death; while in the other 17.8%, sepsis was a contributing cause of death.

Of the 17.8% of infectious disease deaths where sepsis was a contributing cause there were a number of underlying causes of death. For example, sepsis was involved in almost a quarter of all deaths from bacterial infections of the intestines^{Note 28} (e.g., e. coli and c. difficile); and over 10.0% of all deaths from: tuberculosis, viral infections involving skin lesions^{Note 29} (e.g., chickenpox, herpes zoster), HIV and viral hepatitis.

Conclusion

Of all of the Canadians who died in 2011, sepsis played a role in the death of one in 18. Sepsis was more likely to be reported as a contributing cause rather than the underlying cause of death itself. Including both underlying and contributing causes of death when estimating sepsis-associated deaths, allows for a more complete picture of how sepsis plays a role in overall mortality in Canada. It also means that sepsis-associated deaths can be examined using data from the Vital Statistics Program, providing an alternative to special clinical studies and hospitalization-based analyses.

As the Canadian population ages, sepsis is expected to continue to be a major contributor to mortality and an important health care issue.

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