Chapter 5: Life with arthritis in Canada: a personal and public health challenge – Mortality burden of arthritis

Chapter Five: Mortality burden of arthritis

Table of Contents

• Introduction
• Mortality from arthritis among men and women
• Mortality for specific arthritis conditions
• Premature mortality
• Mortality over time
• Summary

Introduction

While deaths from arthritis are rare, people with arthritis, specifically those with severe inflammatory forms, are at increased risk of premature mortality. The most severe inflammatory arthritis conditions including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), sclero- derma, and vasculitis have the highest mortality rates. Individuals with RA are at a higher risk of mortality than the general population, not only because of the disease itself, but because of its associated complications (e.g., cardiovascular disease, infections, renal disease and others).^{Footnote 1 Footnote 2 Footnote 3 Footnote 4 Footnote 5 Footnote 6 Footnote 7 Footnote 8 Footnote 9 Footnote 10} They are also at increased risk of premature death, with a lifespan on average 5–10 years shorter than the general population.^{Footnote 1 Footnote 2 Footnote 11} The systemic nature of inflammatory forms of arthritis can lead to life- threatening complications of the cardiovascular and respiratory systems. In addition, some of the treatments can depress the immune system, leading to increased susceptibility to infection and the risk of immune system related diseases such as cancer.^{Footnote 8 Footnote 10 Footnote 12 Footnote 13 Footnote 14 Footnote 15 Footnote 16}

Mortality rates for this chapter were calculated using the Canadian annual mortality database based on death certificate information for the years of 1999 –2005. The analysis included all deaths for which one of the types of arthritis was recorded as the underlying cause. Mortality rates were calculated for the following five arthritis categories:

• Osteoarthritis (OA);
• Rheumatoid arthritis (RA);
• Other inflammatory arthritis (e.g. gout, psoriatic arthritis, ankylosing spondylitis);
• Connective tissue diseases (e.g. lupus and scleroderma); and
• Other arthritis conditions (e.g. polymyalgia rheumatica, tendonitis, bursitis, synovitis, internal derangement of the knee, other unspecified arthropathies).

The cause of death in people with arthritis may not be recorded as arthritis, but rather as an acute condition or disease1 therefore, it is difficult to determine the true contribution of arthritis to overall mortality.^{Footnote 12 Footnote 13 Footnote 14 Footnote 15 Footnote 16 Footnote 17 Footnote 18 Footnote 19 Footnote 20} For instance, cardiovascular disease, infection or organ failure could have been listed as the underlying cause of death in individuals with inflammatory arthritis whereas, gastrointestinal (GI) bleeding related to anti-inflammatory use or joint infections after joint replacement surgery could have been listed as the underlying cause of death in individuals with OA.^{Footnote 1 Footnote 17 Footnote 18}

Gains in the understanding of mortality as an outcome of arthritis could be realized if the contributing causes of death were included in the Canadian annual mortality database. Such gains would also be important in the areas of diabetes, chronic respiratory diseases, injury and other chronic diseases.^{Footnote 19 Footnote 20}

Mortality from arthritis among men and women

In 2005, 777 women and 296 men in Canada were recorded as having died from arthritis. Mortality rates among men ranged from 0.2 deaths for every 100,000 men aged 54 years or less to 48 deaths per 100,000 men aged 85 years and over (Figure 5-1). Among women in the same age groups, rates ranged between 0.7 deaths per 100,000 to 74 deaths per 100,000. Mortality rates were higher among women than men in every age group, with approximately 2.6 female deaths for every male death.

The number of deaths increased with age, except among men, where the number of deaths declined after the age of 84 years (Figure 5-1). Over one fifth (21%) of the deaths occurred in men and women of working age (0–64 years).

Mortality for specific arthritis conditions

Of the five categories of arthritis conditions, two accounted for over 60% of the total arthritis deaths: connective tissue diseases such as lupus (34%), and RA (30%) (Table 5-1). Among deaths from connective tissue diseases, most were due to lupus or to systemic sclerosis/scleroderma which are two of the less common type of arthritis conditions.

Premature mortality

Premature mortality is defined as death occurring before the age of 75 years. Forty percent of people who died from arthritis (430 deaths) died prematurely (before the age of 75) which is similar to the percentage of Canadians who died prematurely of all causes (39%). Over eighty percent of premature deaths related to arthritis were due to connective tissue diseases (57%) and RA (26%) (Table 5-2).

Premature mortality patterns differed between men and women, reflecting the higher prevalence of connective tissue diseases and RA in women. Among men, 49% of premature deaths were due to connective tissue diseases versus 61% among women, and 23% were due to RA in men compared to 27% for women (Table 5.2).

Several factors influence the risk of early death (premature mortality) including:^{Footnote 11 Footnote 13 Footnote 14 Footnote 15 Footnote 16 Footnote 17 Footnote 18 Footnote 19Footnote 20 Footnote 21}

• physical limitations resulting from the disease;
• markers of disease severity including high number of joints involved, other organ involvement and positive rheumatoid factor in people with RA;
• the presence of other health problems such as cardiovascular diseases, infections, cancer, renal disease, respiratory diseases, gastrointestinal diseases;
• sex (being female); and
• increasing age.

Most of these predictors are associated with premature mortality in the majority of the arthritis types. Preventing premature arthritis deaths involves early diagnosis and recognition, appropriate management and compliance with treatment.^{Footnote 11 Footnote 12 Footnote 17}

Mortality over time

Age-specific mortality rates due to arthritis remained relatively stable from 1999–2005 (Figure 5-2). For those 65 years of age and over, there was a noticeable peak in the year 2000, which could likely be explained by the fact that most provinces and territories in Canada changed their coding classification from ICD-9 to ICD-10 during that year. It may also indicate that ICD-9 and its coding rules could have underestimated the arthritis-related mortality compared to ICD-10. However, no comparability studies have examined the extent to which the change in classification would impact the ascertainment of the causes of death.

Summary

• While deaths from arthritis are rare, in 2005, 777 women and 296 men in Canada died from an arthritis condition: rheumatoid arthritis, systemic lupus erythematosus and other connective tissue diseases accounted for more than 60% of all arthritis deaths.
• Arthritis mortality rates were higher among women than men in every age group, with approximately 2.6 female deaths for every male death in part because these conditions are more common among women.
• Forty percent of people who died from arthritis died prematurely (before the age of 75 years) which is similar to the percentage of Canadians who died prematurely of all causes (39%).
• Age-specific mortality rates due to arthritis remained relatively stable over time (1999–2005).