Trends of Diabetes in Alberta

Transcription

1 Chapter 2 Epidemiological Trends of Diabetes in Alberta Jeffrey A. Johnson Stephanie U. Vermeulen ALBERTA DIABETES ATLAS 27 11

2 12 ALBERTA DIABETES ATLAS 27

3 EPIDEMIOLOGICAL TRENDS OF DIABETES IN ALBERTA KEY MESSAGES Diabetes is a large and growing health problem for Albertans. There are 13, adults living with diabetes in Alberta, which is a doubling of the number ten years ago. There were about 12, new cases of diabetes identified in Alberta in 24. People with diabetes are more than twice as likely to die each year, compared to people without diabetes. Diabetes is most prevalent in the aging population, who tend to have additional health problems that subsequently increase the burden on our health care system. Northern Lights Health Region has the highest age-adjusted prevalence of diabetes in Alberta at 6.8%, while the provincial average is 5.3%. This region also has the highest diabetes incidence in Alberta. BACKGROUND According to the National Diabetes Surveillance System (NDSS), the prevalence of diabetes among adult Canadians in 1999/2 was 5.1%. (1) This means that in 1999/2, there were over 2 million adult Canadians living with diabetes. Canadian adults with diabetes are twice as likely to die prematurely than people without diabetes. These figures are staggering and as we report here, these trends are all too similar while observing the story of diabetes in Alberta. This chapter will examine incidence, prevalence and mortality of those with diabetes in Alberta over the past decade, 1995 to 25. Results will be presented as crude rates, that is, the actual counts and rates on a population basis, as well as age-adjusted rates for the purpose of comparison. Rates will also be presented by health region in order to establish a geographic representation of diabetes across Alberta. These general epidemiological trends of diabetes serve as a starting point when trying to assess the burden of diabetes in Alberta. METHODS In order to interpret the results of this report it is important to understand the terms incidence and prevalence. These concepts along with their formulas are covered in more depth in the Background and Methods Chapter of this Atlas. Incidence is a measure of new cases arising within a particular timeframe. Therefore, diabetes incidence is the number of new cases in Alberta. The incidence rate is the number of new cases of diabetes relative to the total population at risk in each calendar year. ALBERTA DIABETES ATLAS 27 13

4 Prevalence is the number of cases existing within a population at any point in time. Diabetes prevalence includes new and existing cases in Alberta for each calendar year. For example, if an individual becomes incident one year, they are also considered prevalent in that year and every subsequent year. In the current Alberta Diabetes Atlas, we estimated diabetes incidence and prevalence rates based on the total population counts for Albertans registered with Alberta Health and Wellness as of June 3 in each year. The calculated rates are also reported as age-adjusted in order to account for differences in population age structure, or differences in health regions overtime. We used a method of direct standardization (2), using the 21 Canadian Census for Alberta as the reference population. (3) Mortality is reported as the proportion of people who died each year, and is compared between people with and without diabetes. PREVALENCE Figure 2.1 Prevalent Diabetes Cases, Number of Cases 14, 12, 1, 8, 6, Total 71,735 68,562 75,9 78,941 84,624 9,644 97,6 15, ,287 12, ,184 4, 2, Year Nearly 13, adults are living with diabetes in Alberta in 25, a figure that s almost doubled over the last ten years (Figure 2.1). Diabetes was slightly more prevalent in females up to about 21 until it became slightly more prevalent in males. 14 ALBERTA DIABETES ATLAS 27

5 Figure 2.2 Age-Adjusted Diabetes Prevalence Rates, Total 4 Rate per Year The prevalence of diabetes has been steadily increasing in both males and females over the past decade. In 25, the unadjusted prevalence of diabetes in Alberta adults was 5.5%. Adult males experience a slightly higher prevalence than females. Over the 1995 to 25 period, the male age-adjusted rate increased by 43.9% overall, while the female rate increased by 37.6% (Figure 2.2). Figure 2.3 Age Distribution of Prevalent Diabetes Cases, Number of Cases Total Population Distribution Age Group (Years) Due to the chronic nature of diabetes the number of cases increases as people become older, peaking in age group (Figure 2.3). When people with diabetes become older than 59 years, the prevalence remains high, but begins to decrease, presumably as people die. ALBERTA DIABETES ATLAS 27 15

6 cases outnumber female cases beginning in age group 5-54 years until age group From age groups 8 and older, diabetes is more prevalent in females cases, perhaps due to women having longer life expectancies. cases also have a much higher prevalence of diabetes in the younger ages until about ages This is due, in part, to the risk of gestational diabetes during women s childbearing years. Women who develop gestational diabetes are at increased risk of subsequently developing type 2 diabetes. (4) 25 Figure 2.4 Age-Specific Diabetes Prevalence Rates, 25 2 Total Rate per Age Group (Years) Diabetes prevalence rates increases with age in both sexes, rising considerably after ages (Figure 2.4). Prevalence rates peak in the age group, approaching 16% in females and 19% in males. This is a substantial increase over the 2-29 age group, where prevalence is less than 1%. Diabetes prevalence in females is slightly higher than in males, until about age 5, when prevalence in males becomes higher. 16 ALBERTA DIABETES ATLAS 27

7 Figure 2.5 Age-Adjusted Diabetes Prevalence Rates by Region, Total 6 Rate per Chinook Palliser Calgary David Thompson East Central Capital Aspen Peace Country Region Northern Lights The age-adjusted prevalence of diabetes varies across the province. The highest rates are in the Northern Lights region at 6.8%, and the lowest rates in the Calgary region at 4.7% (Figure 2.5 and 2.6). The average provincial age-adjusted prevalence rate is 5.3%. Calgary, David Thompson and East Central all have an age-adjusted prevalence rate below the provincial average while Chinook, Palliser, Capital, Aspen, Peace Country and Northern Lights have rates above. Diabetes prevalence rates are generally higher in males except for the three most northern regions of Aspen, Peace Country and Northern Lights where rates are higher in females. Figure 2.6 Age-Adjusted Diabetes Prevalence Rates by Region, 25 8 Peace Country 9 Northern Lights 7 Aspen 6 Capital 4 David Thompson 5 East Central Much higher that provincial average Higher than provincial average Average Lower than provincial average Much lower than provincial average 3 Calgary 1 Chinook 2 Palliser ALBERTA DIABETES ATLAS 27 17

8 Prevalence differences among Alberta s health regions should be interpreted with caution due to the effects of different populations and access to care issues. For example, diabetes prevalence in First Nations people is higher than for non-first Nations people, and there are a larger proportion of First Nations people living in Northern Alberta and Southern Alberta. This may in part explain why the highest rates of diabetes are in Northern and Southern Alberta. This concept will be further discussed in the First Nations chapter of the Atlas. As well, access to care is believed to be limited in rural Alberta, and because the ADSS is not able to capture sub-clinical cases which are undetected or undiagnosed, only diagnosed cases are reported in incidence and prevalence estimates. INCIDENCE During the time period , there were more than 86, new cases of diabetes identified in Alberta (Figure 2.7). The number of diabetes cases identified in 24 (n=11,927) was almost double that of the new cases identified in 1995 (n=664). Figure 2.7 Incident Diabetes Cases, , Number of Cases 12, 1, 8, 6, Total 6,64 6,82 6,257 7,17 8,389 9,169 1,142 1,848 1,563 11,927 4, 2, Year After adjusting for age, the incidence of diabetes appears to be increasing steadily over the past decade, with more new cases being diagnosed in males compared to females across the years (Figure 2.8). 18 ALBERTA DIABETES ATLAS 27

9 Figure 2.8 Age-Adjusted Diabetes Incidence Rates, Total 5 Rate per Year Diabetes incidence increases with age until 7-74 years in males and years in females, after which it decreases (Figure 2.9). Women aged 2-34 years have a greater proportion of incident cases than men. Gestational diabetes cases in a woman s childbearing years likely accounts for this increase in incidence cases among women compared to men in these ages. However, males have increased diabetes incidence compared to females across all ages beginning at years until 85+ years. Figure 2.9 Age-Specific Diabetes Incidence Rates, Cases per Age Group (Years) ALBERTA DIABETES ATLAS 27 19

10 Figure 2.1 Age-Adjusted Diabetes Incidence Rates by Region, Total 8 Rate per Chinook Palliser Calgary David Thompson East Central Capital Aspen Peace Country Region Northern Lights As with prevalence, age-adjusted diabetes incidence varies across the province (Figure 2.1 and 2.11). In 24, the highest incidence rates were in the Northern Lights region at 7.5 new diabetes cases per 1 people. The lowest rates were in East Central with 5 cases per 1. As a point of reference, the average provincial age-adjusted incidence rate is 5.5 cases per 1. s have a greater proportion of diabetes incidence than females across all regions in Alberta. Figure 2.11 Age-Adjusted Diabetes Incidence Rates by Region, 24 8 Peace Country 9 Northern Lights 7 Aspen 6 Capital 5 East Central 4 David Thompson Much higher that provincial average Higher than provincial average Average Lower than provincial average Much lower than provincial average 3 Calgary 1 Chinook 2 Palliser 2 ALBERTA DIABETES ATLAS 27

11 MORTALITY The mortality rates among people with diabetes are higher than the mortality rates among people without diabetes. The ratio between the two rates reflects the significance of diabetes on overall mortality. Figure 2.12 Age-Adjusted Mortality Rates, s with Diabetes s with Diabetes s without Diabetes s without Diabetes Rate per Year While mortality rates for both sexes have decreased over the years, perhaps due in part to the general population s life expectancy increasing, it is apparent that those who have diabetes have much higher mortality rates than those without diabetes, regardless of sex (Figure 2.12). In the past decade, the overall mortality rates have consistently been over twice as high in the diabetic population compared to those without diabetes. Men have higher mortality rates than women through the years, but having diabetes amplifies this difference. While diabetic men have higher mortality rates than women with diabetes, the difference appears to have lessened in recent years. ALBERTA DIABETES ATLAS 27 21

12 Figure 2.13 Age-Specific Mortality Rates, Rate per Deaths with Diabetes Deaths without Diabetes Rate Ratio (Diabetes: No Diabetes) Age Group (Years) Mortality rates for those who have diabetes are consistently higher at all ages than mortality rates for those who do not have diabetes (Figure 2.13). Both individuals with and without diabetes have higher mortality rates as they become older. The mortality rate ratio demonstrates that younger people with diabetes have a much higher risk of dying compared to older individuals who have diabetes. In fact, individuals between the ages of 3-34 years are 6.7 times more likely to die if they have diabetes whereas, people 65 years or older are less than 2 times more likely to die if they have diabetes. This reduction in the relative risk of death is likely due to competing causes of death in the older ages. DISCUSSION The observed trends for the number of Albertans living with diabetes follow similar trends for the rest of Canada (1), the US (5), and the rest of the world. (6,7) This confirms that diabetes is a large and growing health problem. Of particular note is the doubling in the number of people living with diabetes in Alberta over the past decade. The prevalence of diabetes is increasing because of the growing numbers of new cases each year, and because those who have diabetes are living longer. While people with diabetes are still 2 to 4 times more likely to die than people without diabetes, the mortality rates over the past decade have declined, which is encouraging. This trend is likely due to fewer heart attacks and strokes for people with diabetes, which has also been seen in other parts of Canada. (8) The troubling news is that while the heart attack and stroke rates have declined, the actual number of heart attacks and strokes are increasing as the number of people with diabetes grows. 22 ALBERTA DIABETES ATLAS 27

13 While the information presented in the Alberta Diabetes Atlas provides a valuable representation of the burden of diabetes in our province, we recognize that there are several important limitations in using the administrative data from Alberta Health and Wellness. We have used a case definition to identify people with diabetes that requires individuals to have been diagnosed with diabetes by a physician, or be admitted to hospital. It is well recognized that many people who have diabetes are not yet diagnosed. (9,1) Further, there are likely some individuals who have been diagnosed with diabetes and are relatively healthy who have not seen a physician frequently enough to qualify as a diabetes case under the current definition. Because of these limitations, it is regarded that the ADSS, our surveillance system, generally underestimates the true burden of diabetes on a population basis. Nonetheless, in applying the case definition in a consistent way across the time period, we can be confident that we are observing the true trends of the epidemiology of diabetes in Alberta. Surveillance systems such as the ADSS are intended to provide a broad, populationbased perspective. That said, these first impressions may guide further detailed surveillance where data anomalies or interesting patterns can be explored in greater detail. For example, gestational diabetes is a special form of diabetes which is included in the ADSS case definition. The NDSS excludes cases of gestational diabetes, (1) hence the prevalence and incidence of diabetes in younger female Albertans may appear higher than national estimates. We chose to include women with gestational diabetes as they have an increased risk of subsequently developing type 2 diabetes later in life. (4) Furthermore, gestational diabetes also puts the newborn infant at increased health risks. (4) By including women with gestational diabetes in this first version of the Alberta Diabetes Atlas, we will be able to monitor their future health status, including the health of their offspring. Presenting the number of cases with diabetes over the past decade also provides us with a hint of what we can expect for the future. Without tremendous effort by our social and public health care systems, it is entirely likely that the upward trends in both incidence and prevalence of diabetes will continue for the next decade. Like the rest of Canada and the world, the prevalence of diabetes in Alberta could more than double again in the next 5 to 6 years. CONCLUSION Information such as the trends presented here should be viewed as a call to action. Provincial and regional decision-makers will find this information useful in the consideration and evaluation of efforts to curb the burden of diabetes. Information available in future versions of the Alberta Diabetes Atlas will tell us how well we are doing in achieving that goal. ALBERTA DIABETES ATLAS 27 23

14 References 1. Health Canada. 2nd Report on the National Diabetes Surveillance System. 27. Ottawa, Health Canada. 2. Hennekens CH, Buring JE: Epidemiology in Medicine. Philadelphia, Lippincott Williams & Wilkins, Statistics Canada: Age and Sex for Population, for Canada, Provinces, Territories, Census Metropolitan Areas and Census Agglomerations, 21 Census. [article online], 27. Accessed Catalog Number: 95F3XCB Canadian Diabetes Association Clinical Practice Guidelines Expert Committee, Canadian Diabetes Association: Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada. Canadian Journal of Diabetes 27:S99-S15, Mokdad AH, Ford ES, Bowman BA, Dietz WH, Vinicor F, Bales VS, Marks JS: Prevalence of obesity, diabetes, and obesityrelated health risk factors, 21. JAMA 289:76-79, Shaw JE, Zimmet PZ, McCarty D, de Court: Type 2 diabetes worldwide according to the new classification and criteria. Diabetes Care 23 Suppl 2:B5-1, 2 7. Zimmet P, Alberti KG, Shaw J: Global and societal implications of the diabetes epidemic. Nature 414: , Booth GL, Kapral MK, Fung K, Tu JV: Recent trends in cardiovascular complications among men and women with and without diabetes. Diabetes Care 29:32-37, Harris MI, Flegal KM, Cowie CC, Eberhardt MS, Goldstein DE, Little RR, Wiedmeyer HM, Byrd-Holt DD: Prevalence of diabetes, impaired fasting glucose, and impaired glucose tolerance in U.S. adults. The Third National Health and Nutrition Examination Survey, Diabetes Care 21: , Rathmann W, Haastert B, Icks A, Lowel H, Meisinger C, Holle R, Giani G: High prevalence of undiagnosed diabetes mellitus in Southern Germany: target populations for efficient screening. The KORA survey 2. Diabetologia 46: , ALBERTA DIABETES ATLAS 27