Global Prevalence of Ankylosing Spondylitis
Global Prevalence of Ankylosing Spondylitis
Objectives. For effective health care provision, knowledge of disease prevalence is paramount. There has been no systematic endeavour to establish continent-based AS estimates, however, prevalence is thought to vary by country and background HLA-B27 prevalence. This study aimed to estimate AS prevalence worldwide and to calculate the expected number of cases.
Methods. A systematic literature search was conducted. Prevalence data were extracted and used to calculate the mean prevalence by continent and the expected number of cases based on country-specific prevalence (or, if missing, the prevalence from neighbouring countries). A second estimate was made using the prevalence from countries with similar HLA-B27 prevalences if a country-specific prevalence estimate was not available.
Results. The mean AS prevalence per 10,000 (from 36 eligible studies) was 23.8 in Europe, 16.7 in Asia, 31.9 in North America, 10.2 in Latin America and 7.4 in Africa. Additional estimates, weighted by study size, were calculated as 18.6, 18.0 and 12.2 for Europe, Asia and Latin America, respectively. There were sufficient studies to estimate the number of cases in Europe and Asia, calculated to be 1.30–1.56 million and 4.63–4.98 million, respectively.
Conclusion. This study represents the first systematic attempt to collate estimates of AS prevalence into a single continent-based estimate. In addition, the number of expected cases in Europe and Asia was estimated. Through reviewing the current literature, it is apparent that the continuing conduct of epidemiological studies of AS prevalence is of great importance, particularly as diagnostic capabilities improve and with the recent development of the criteria for axial SpA.
AS is an inflammatory arthritis within a family of related disorders (SpA) including PsA, reactive arthritis, SpA associated with IBD and uSpA. These SpAs exhibit a similar genetic background, clinical features and symptoms. The prognosis for patients with AS is variable and is determined, in part, by the presence of a number of extraspinal manifestations (such as uveitis, psoriasis and IBD), the age at diagnosis and the treatment provided. Generally AS results in serious impairment of spinal mobility and physical function, which has an impact on quality of life.
AS usually initially presents during the third decade of life, and rarely after the age of 45 years. The prevalence of AS is generally believed to be between 0.1% and 1.4% globally, although it is difficult to be certain, as few prevalence studies have been conducted compared with other rheumatic disorders such as RA. In addition, to date there have been no systematic attempts to collate data from the available studies of AS prevalence. The disease is thought to exhibit a higher prevalence among those of lower socioeconomic status, who are also more likely to have poor functional outcomes. Reviews have highlighted the global variation in the background prevalence of the known AS risk allele HLA-B27 and, as 90% of AS patients exhibit this variant, there is also likely to be geographical differences in disease prevalence. Additionally there is some gender disparity within AS, with reported gender ratios of around 2:1 (male:female), although this estimate has also been shown to vary considerably between studies and across time.
For the effective provision of health care, knowledge of disease prevalence is paramount, therefore this study aims to determine the global prevalence and gender ratio of AS by collating studies for each world region. In addition, the total estimated number of cases within the continents will be estimated where sufficient numbers of studies of AS prevalence are available.
Abstract and Introduction
Abstract
Objectives. For effective health care provision, knowledge of disease prevalence is paramount. There has been no systematic endeavour to establish continent-based AS estimates, however, prevalence is thought to vary by country and background HLA-B27 prevalence. This study aimed to estimate AS prevalence worldwide and to calculate the expected number of cases.
Methods. A systematic literature search was conducted. Prevalence data were extracted and used to calculate the mean prevalence by continent and the expected number of cases based on country-specific prevalence (or, if missing, the prevalence from neighbouring countries). A second estimate was made using the prevalence from countries with similar HLA-B27 prevalences if a country-specific prevalence estimate was not available.
Results. The mean AS prevalence per 10,000 (from 36 eligible studies) was 23.8 in Europe, 16.7 in Asia, 31.9 in North America, 10.2 in Latin America and 7.4 in Africa. Additional estimates, weighted by study size, were calculated as 18.6, 18.0 and 12.2 for Europe, Asia and Latin America, respectively. There were sufficient studies to estimate the number of cases in Europe and Asia, calculated to be 1.30–1.56 million and 4.63–4.98 million, respectively.
Conclusion. This study represents the first systematic attempt to collate estimates of AS prevalence into a single continent-based estimate. In addition, the number of expected cases in Europe and Asia was estimated. Through reviewing the current literature, it is apparent that the continuing conduct of epidemiological studies of AS prevalence is of great importance, particularly as diagnostic capabilities improve and with the recent development of the criteria for axial SpA.
Introduction
AS is an inflammatory arthritis within a family of related disorders (SpA) including PsA, reactive arthritis, SpA associated with IBD and uSpA. These SpAs exhibit a similar genetic background, clinical features and symptoms. The prognosis for patients with AS is variable and is determined, in part, by the presence of a number of extraspinal manifestations (such as uveitis, psoriasis and IBD), the age at diagnosis and the treatment provided. Generally AS results in serious impairment of spinal mobility and physical function, which has an impact on quality of life.
AS usually initially presents during the third decade of life, and rarely after the age of 45 years. The prevalence of AS is generally believed to be between 0.1% and 1.4% globally, although it is difficult to be certain, as few prevalence studies have been conducted compared with other rheumatic disorders such as RA. In addition, to date there have been no systematic attempts to collate data from the available studies of AS prevalence. The disease is thought to exhibit a higher prevalence among those of lower socioeconomic status, who are also more likely to have poor functional outcomes. Reviews have highlighted the global variation in the background prevalence of the known AS risk allele HLA-B27 and, as 90% of AS patients exhibit this variant, there is also likely to be geographical differences in disease prevalence. Additionally there is some gender disparity within AS, with reported gender ratios of around 2:1 (male:female), although this estimate has also been shown to vary considerably between studies and across time.
For the effective provision of health care, knowledge of disease prevalence is paramount, therefore this study aims to determine the global prevalence and gender ratio of AS by collating studies for each world region. In addition, the total estimated number of cases within the continents will be estimated where sufficient numbers of studies of AS prevalence are available.
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