Background Trends in the incidence of RA may reflect changes in the host-environment relationship.
Objectives To assess the incidence of seropositive rheumatoid arthritis (RA) during 30 year period in Northern Savo Finland and to evaluate the role of dental health on the incidence.
Methods The incidence of seropositive RA was evaluated on the basis of epidemiological data collected from the previous and current studies in Northern Savo area from years 1980, 1990, 2000 and 2010. Serum samples from 134 and 175 arthritis patients were collected in two studies on inflammatory joint diseases in 2000 and 2010, respectively. As markers of periodontal disease serum immunoglobulin A (IgA) and IgG –class antibodies against Aggregatibacter actinomycetemcomitans (Aa) and Porphyromonas gingivalis (Pg) were determined in various diagnostic categories.
Results A total of 196 subjects suffered from seropositive RA that had started at the age of 16 or over in 1980, 1990, 2000 or 2010. The incidence rate ratio of seropositive RA decreased in the age group of 35-54 years and increased in the older age groups. The levels of Aa and Pg antibodies did not differ between the diagnostic categories. In 2010, 66.7 % of patients with seropositive RA and 26.7 % of patients with seronegative RA showed elevated levels of PgIgA antibodies, p=0.014. The age, gender and diagnosis adjusted levels of AaIgA, PgIgA, PgIgG antibodies between years 2000 and 2010 showed significant decrease, P=0.011, <0.001, 0.011, respectively. In the age group of 35-54 years in all disease categories the decrease in PgIgA and PgIgG levels occurred only in women.
Conclusions The declining trend for the incidence of seropositive RA occurred in the age-group of 35-54 years. Carriage of periodontal pathogens or a high prevalence of other infectious diseases may have influence on the risk of developing seropositive RA which could be reduced by public health measures.
References Kaipiainen-Seppänen O, Kautiainen H. Declining trend in the incidence of rheumatoid factor-positive rheumatoid arthritis in Finland 1980-2000. J Rheumatol. 2006;33:2132-8.
Disclosure of Interest None Declared