How Common is Gout in the United States, Really?
How Common is Gout in the United States, Really?
The prevalence and incidence of gout varies widely around the world, with developed countries generally having higher prevalence than developing countries. A combination of genetic and environmental factors contributes to the development of gout, according to a review of literature published in the November issue of Nature Reviews Rheumatology.
Gout, the most common form of inflammatory arthritis, is caused by the deposition of monosodium urate crystals in and around the joints. According to this review of contemporary epidemiology of gout since 2007, the reported prevalence of gout worldwide ranges from 0.1% to approximately 10%, and the incidence from 0.3 to 6 cases per 1,000 person-years.
Prevalence of gout worldwide
Gout is common in most countries in North America and Western Europe, with prevalence in the 1–4% range. In the United States, 3.9% of the adult population (age ≥20 years) self-reported gout between 2007–2008, according to one study cited in the review.
“The prevalence of gout in more affluent countries seems to be increasing in recent decades. However, only a few studies give reliable data on secular trends in gout prevalence. The US NHANES study found a significantly higher age-adjusted prevalence (3.9%) in 2007–2008 than the estimate in 1988–1994 (2.9%). This trend paralleled an observed increase in hyperuricaemia,” the authors wrote.
In a larger study of 11,963 patients aged 45–64 years who were followed from 1987 to 2012, estimated the incidence of gout at 0.84 per cases 1,000 person-years.
But the highest prevalence worldwide is reported in Taiwanese aboriginals and Maori, with some estimates of more than 10%. Gout is reportedly rare in former Soviet Union regions, Guatemala, Iran, Malaysia, Philippines, Saudi Arabia, rural Turkey and African countries, the authors note.
The prevalence of gout in more affluent countries seems to be increasing in recent decades. This trend parallels an observed increase in hyperuricaemia. Although there are sparse data on the prevalence of gout in developing countries, in general, gout prevalence appears to be lower in these countries than in more affluent ones, the authors wrote.
The incidence of gout generally increases with age, reaching a plateau after age 70. In general, gout incidence is 2‒6-fold higher in men than in women. A few studies in the U.S. and United Kingdom indicate that gout incidence seems to have increased since the 1990s, but little data are available on the incidence of gout in other countries.
Risk factors of gout
The authors also outline the major risk factors for gout, which include hyperuricaemia, genetics, dietary factors, medications, comorbidities and exposure to lead.
"The two major factors that predispose to MSU crystal formation are chronic hyperuricaemia and local tissue characteristics that facilitate MSU crystal nucleation and growth. That a genetic component contributes to the development of gout is supported by clinical and epidemiological evidence, as well as recent advances in genetic studies,” the authors wrote.
They suggest that regional variations in gout distribution might be explained, at least in part, by ethnicity, prevalence of metabolic syndrome and dietary factors. Ethnic background clearly affects gout prevalence and incidence and supports a substantial genetic predisposition to gout, they state.
In terms of risk by sex, it is widely known that gout is more common in men, but in women, the risk increases sharply after menopause. “In men, the risk of gout increases steadily with age, but in women, who have a lower prevalence of gout than men at all ages, the risk increases sharply after menopause. The reason behind the large difference in gout risk in men and women might relate largely to the uricosuric action of oestrogen,” the authors wrote.
Numerous studies have shown a link between gout and comorbidities, such as the metabolic syndrome, cardiovascular disease and renal diseases. “For instance, obesity as a part of the metabolic syndrome, is consistently reported to increase risk of gout. The cumulative incidence of gout at age 70 was 11.8% in women with BMI ≥35 kg/m2, compared with only 1.9% in those with BMI <25 kg/m2,” the authors wrote.
Research has also shown that gout is more common in patients with psoriasis and sickle cell anaemia, “presumably due to increased cell turnover and subsequent tendency to increased levels of SUA,” which can also be driven by medications such as ciclosporin and tacrolimus (both used for immunosuppression) and diuretics. “A study using the CPRD found that loop, thiazide and thiazide-like diuretics were associated with odds ratios for incident gout of 2.64, 1.70 and 2.30, respectively, and the combination of a loop diuretic and a thiazide diuretic was associated with an approximately fivefold increased risk of incident gout,” the authors wrote.
In conclusion, the authors note that gout is a complex disorder with a mix of both genetic and environmental risk factors, which leads to challenges in acquiring accurate epidemiologic data.