Autoimmune diseases prevalence

Many environmental factors have been implicated in the induction of autoimmunity. One dietary component, iodine, has been well studied as a factor that increases autoimmune thyroid disease.67 68 Based on studies in the OS chicken, the increasing prevalence of autoimmune thyroid disease observed in U.S. and Western European populations has been ascribed to increased use of iodized salt.69 Experimentally, it can be shown that iodinated thyroglobulin is a more potent autoantigen than the equivalent noniodinated molecule. Food additives or pesticides may also be important in contributing to the development of autoimmune disease in susceptible individuals.70... 

Prevalence, Sex Distribution, Autoantibody Targets and Major Areas of Environmental Research Concerning Selected Autoimmune Diseases. 

In the adult population, the prevalence of overt hypothyroidism is 19 per 1000 women and 1 per 1000 men with annual incidence of overt hypothyroidism is 4 per 1000 women and 0.6 per 1000 men. Subclinical hypothyroidism is also more common in women, the incidence increases with age, with up to 10% of women older than 60 years having an increased thyroid-stimulating hormone concentration. Subclinical hypothyroidism is more common in people who have been treated for hyperthyroidism with radioactive iodine or surgery, and in those with organ-specific autoimmune diseases, such as pernicious anaemia, type 1 diabetes mellitus, or Addison s disease. 

Hypothyroidism, a condition in which the circulating concentrations of thyroid hormones are too low, is the most prevalent thyroid disease. Primary hypothyroidism, the commonest form, is an autoimmune disease (Hashimoto s thyroiditis) often associated with goitre. Like other autoimmune diseases, it is more prevalent in women (4 per 1000) than in men (1 per 1000). Other causes include thyroidectomy, radioac tive ablation and, in some countries, iodine deficiency. Hypothyroidism can also be caused by several drugs, including lithium, interleukin-2 and interferon. Secondary hypothyroidism is a disease caused by decreased secretion of TSH by the pituitary. 

In autoimmune diseases cyclophosphamide can cause menstrual disorders (oligomenorrhea or sustained amenorrhea) and ultimately sterihty or premature menopause. This has been particularly exemplified in lupus erythematosus, and several studies have shown a high prevalence of menstrual disorders or premature ovarian failure in cyclophosphamide-treated patients, or a significantly higher incidence of both complications compared with other immunosuppressive regimens or healthy controls (31-33). 

Rheumatoid arthritis is a chronic, inflammatory, autoimmune disease of unknown etiology that if left untreated results in progressive joint destruction, deformity, disability, and premature death. Theories of possible etiologies include genetic, hormonal, viral, autoimmune, and environmental factors. The disease peaks between the fourth through sixth decades of life and is two to three times more common in women than in men. Differences in prevalence rates between ethnic groups are small. 

Type 2 Diabetes Mellitus This is the most prevalent form of diabetes and is characterized by both an insulin secretion defect and insulin resistance. Maturity-onset diabetes of the young (MODY), attributable to mutations of the glucose kinase gene (discussed earlier), may also be classified as type 2 diabetes mellitus. Obesity is a contributory factor and may predispose to insulin resistance with eventual development of type 2 diabetes mellitus. The precise mechanism by which obesity leads to insulin resistance in the target tissues is not understood. However, in several animal models (e.g., ob/ob mouse, db/db mouse) mutations have been identified that cause both obesity and diabetes mellitus. Unlike type 1 diabetes mellitus, type 2 is not an autoimmune disease. Studies with monozygotic twins have revealed a 90% concordance rate for type 2 diabetes mellitus, suggesting the involvement of genetic factors in the development of the disease. 

Generally, autoimmune diseases are perceived to be rare however, when all autoimmune diseases are combined, the estimated prevalence of 3-5% is not rare, which underlines their importance in the public health sector. Because of problems in designing and standardizing epidemiological studies and because of the fact that only limited data are available, this prevalence may be underestimated (Jacobson et al., 1997). There is epidemiological evidence of increasing prevalence of some autoimmune diseases (e.g. diabetes mellitus type 1, multiple sclerosis), although the rates for other diseases (specifically, rheumatoid arthritis, or RA) appear to be... 

A recent review of epidemiological studies covering 24 specific autoimmune diseases estimated that approximately 3% of the population in the United States suffers from an autoimmune disease (Jacobson et al., 1997). This estimate is likely to be low, as for many diseases our knowledge of basic epidemiology is quite limited or based on studies conducted 30 or more years ago, and some diseases (e.g. psoriasis) were not included in this summary. A revised estimate of the prevalence of autoimmune diseases presented in a recent report of the United States National Institutes of Health (2000) is 5-8%. Comparable figures for other countries are not available. 

Many specific autoimmune diseases are relatively rare, with an estimated incidence of less than 5 per 100 000 persons per year or an estimated prevalence of less than 20 per 100 000 (Table 7). Other diseases (e.g. rheumatoid arthritis, Graves disease, thyroiditis) are quite common, affecting 1% or more of the population (Cotch et al., 1996 Boberg et al., 1998 Cooper et al., 1998 Marie et al., 1999 Boisseau-Garsaud et al., 2000 Watts et al., 2000 Pillemer et al., 2001 Doran et al., 2002 Kalb et al., 2002 Lovas Husebye, 2002 Feld Heathcote, 2003 Gonzalez-Gay et al., 2003 Mayes et al., 2003 Bogliun Beghi, 2004 Cuadrado et al., 2004). 

Studies of autoantibodies in the general population allow us to determine the prevalence of specific autoantibodies among people who do not have a clinically evident autoimmune disease, whether the prevalence of autoantibodies reflects the demographic variation in disease risk and whether specific environmental exposures are related to the expression of specific autoantibodies. These studies are most feasible for the autoantibodies associated with the most common autoimmune diseases diabetes mellitus type 1, autoimmune thyroid disease, and rheumatoid arthritis. Important issues with respect to interpreting these types of studies include the type of test used and definition of a positive result. 

There is epidemiological evidence of increasing incidence and prevalence of certain autoimmune diseases in highly industrialized countries, which cannot be attributed to better diagnostics alone. 

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