Developed countries have better systemic lupus erythematosus survival rates than developing countries, or countries with lower economic performance. This is in part because of a higher human development index, defined by standard of living (a marker for gross domestic product), literacy rates, and life expectancy, with contribution from ethnic variations within individual countries, and unique environmental factors.
Systemic lupus erythematosus (SLE) has been reported from most countries around the world. Epidemiologic studies have detailed worldwide SLE incidence and prevalence, along with the effects of gender, race, and age on presentation and mortality. It is known that developed countries, which have a high gross domestic product (GDP), have significantly better survival rates than developing countries, defined as those having lower economic performances. However, this does not explain differences in SLE outcomes among countries of varying GDPs, which are in part due to factors such as access to health care, physician availability, educational level, and treatment compliance. The human development index (HDI) provides a more three-dimensional view of life, by addressing the previously mentioned factors. The HDI accounts not just for standard of living (an indirect marker of GDP), but also literacy rates (a measure of educational levels), and life expectancy (an index of a population’s quality of health and access to health care).
There is no clear definition of a developed country. For the sake of this article, however, the authors include Western Europe, the United States of America, Canada, Japan, South Korea, Singapore, Kuwait, and the United Arab Emirates, all of which share a universally high GDP and very high HDI.
Within the developing countries, China, India, South Africa, Brazil, Mexico, and a few Southeast Asian countries are separately categorized as newly industrialized countries, as they have outpaced their counterparts in the developing world in terms of economic growth and social development. The newly industrialized countries have medium- to high-level HDIs, with rapidly growing GDPs. Finally, excluding South Africa and Tunisia, many of the countries of sub-Saharan Africa have among the lowest GDPs and HDIs in the world, and are thus considered least developed among the developing countries.
Outcomes in SLE survival depend on a complex interplay of many factors. In this article, the authors have categorized countries by HDI and GDP, to correlate the effects of both social and economic prosperity with SLE outcomes.
SLE in the developed world
Since the 1990s, several lupus registries have been established, most in the developed world. Within the German Collaborative Arthritis Database, 5% of the patients have SLE. Five-year SLE survival rates from Germany are reported as high as 96.6%, with a 10-year survival rate between 83% and 90%. In a small cohort of lupus nephritis patients in Germany, those diagnosed in the 1990s, compared with patients diagnosed in the 1980s, had significantly lower proteinuria, lower rates of renal failure, and less chronicity on kidney biopsy histopathology, due to earlier diagnosis and treatment. In 1999 Camilleri reported his experience with 62 SLE patients from Malta, the country with the lowest GDP of the high HDI European countries ( Table 1 ). The duration of follow-up, however, was not reported, and about 10% of the patients died. In a pan-European cohort of 187 SLE patients with disease duration of greater than 10 years, renal and central nervous system (CNS) involvement increased to 47% and 65%, respectively, while cutaneous, musculoskeletal, and hematologic manifestation rates remained stable.
|GDP per Capita 1990 in US Dollars||GDP per Capita in 2008 in US Dollars||Government Health Care Expenditure as Percent of Total Expenses||HDI||Number of Physicians per 10,000 Population||SLE 5-year Survival||SLE 10-year Survival||Percentage of Patients in the Cohort with Lupus Nephritis|
|United States||32,132.00||43,156.00||19.3%||VH (0.956)||26||97%||93%||28%–38%|
|EuroLupus cohort||21,966.71||31,595.71||14.2%||VH (0.923)||30||NA||92%||28%|
|South Korea||8,761.00||19,716.00||6.0%||VH (0.937)||33||93%||NA||37%|
|United Arab Emirates||29,514.00||34,207.00||8.7%||VH (0.903)||17||94%||NA||51%|
|Newly industrialized countries|
|South Africa||4062.00||5183.00||9.1%||M (0.683)||8||57%–72%||NA||44%|
|Saudi Arabia||12,296.00||12,369.00||8.7%||H (0.843)||14||98%||97%||47.5%|
|Sri Lanka||652.00||1315.00||8.3%||M (0.759)||6||93.4% (3-year survival)||69%|
|Zimbabwe||52.00||29.00||8.9%||M (0.513)||2||71% (1-year survival)||71%|
The EuroLupus project consisting of 1000 patients from Western and European countries is perhaps the best-known European lupus registry. Within this cohort, active lupus nephritis was seen in 27.9% of patients. The 10-year survival rate was 92%, with deaths caused by active SLE in 26.5% of patients, infections in 25%, and thromboses (cerebral, coronary, and pulmonary) in 26.5%. The cause of death in SLE patients is increasingly attributed to cardiovascular events rather than active disease, probably due to increased survival.
Japan’s national SLE registry of over 50,000 patients has survival rates mirroring that of other developed countries. SLE survival in Japan has improved from 72% in the 1950s and 1960s to 94% by the 1980s. Also noted was the decrease in death from active SLE over time, while deaths caused by fatal infections and pulmonary hypertension (PAH) increased.
As seen in German studies, even though the 5-year survival rates were at 93%, the overall SMR (standardized mortality ratio) was 3.02. The most common causes of death were PAH and interstitial lung disease. Another cohort from South Korea reported infection (gram-negative bacilli), active SLE, and PAH as the main causes of mortality in patients.
Ethnic Diversity and SLE Outcomes in Developed Countries
Singapore has a diverse population consisting mainly of Chinese (70% to 80%), followed by Malays and Indians. In a retrospective review of 67 SLE patients from 1992 to 1995, active SLE and infection (gram-negative bacilli and tuberculosis) each accounted for over 40% of deaths.
United States of America and Canada
Unlike Europe, which has a predominantly white cohort, the United States and Canada have increasingly diverse patient populations. People identified as belonging to minority ethnic populations within developed countries have higher prevalence of SLE, more severe disease manifestations, and younger age at onset of disease. These populations also tend to belong to a lower socioeconomic stratum and have a lower survival rate than the white population.
Systemic Lupus Erythematosus International Collaborating Clinics (SLICC) is an SLE registry that includes patients from the United States and Canada, along with other developed countries such as South Korea and the United Kingdom. Bernatsky and colleagues reported in 2006 that SLE patients had a higher SMR of 2.4. When this was further broken down by race for patients from the United States, African Americans had a higher SMR (2.6) than whites (SMR of 1.4).
The Lupus in Minorities: Nature versus nurture (LUMINA) cohort was started in 1994 to study the epidemiology of SLE in three different ethnic groups: Hispanics, African Americans, and whites, enrolling patients from the United States, and Puerto Rico. Lupus nephritis also was found to be at least two times more prevalent among African Americans and Hispanics than whites. Among Hispanics, Texan Hispanics, who are of American Indian/Mestizo descent, had more serositis (60% vs 8.6%), renal involvement (41% vs 13.6%), and overall disease activity, than Puerto Rican Hispanics, who are of mixed white/African/American Indian descent. Nonwhite patients also were found to be more likely to be living below the poverty line, less educated, and more noncompliant with clinic visits.
SLE prevalence has been reported to be much more prevalent in those of African ancestry within the developed countries. Even though Afro-Caribbeans and Asians had similar high rates of lupus nephritis (>55%) in a Canadian cohort, Afro-Caribbeans had higher damage scores and damage accumulation than Asians. Afro-Caribbeans also had lower household income and educational level than the other ethnic groups.
In Hawaii, the prevalence of SLE was found to be higher in all three major Asian groups: Chinese, Filipinos, and Japanese, when compared with whites. In addition, the Asian group had a threefold higher mortality rate than whites. Kaslow found that the age- and sex-adjusted mortality rates were three times higher for African Americans and two times higher for the Asian population, compared with the Caucasian population.
Kuwait and the United Arab Emirates enjoy a high GDP, very high HDI, and a high number of physicians per 10,000 population ( Table 1 ). These countries have a majority expatriate population from other Arab and South Asian countries. Al-Jarallah and colleagues reported a 99% 5-year survival rate for their SLE patients from Kuwait. AlSaleh and colleagues reported a similarly high 5-year survival rate for patients from Dubai, in the United Arab Emirates.