Chlamydial antibodies in an elderly Finnish population.

The characteristic feature of Chlamydia is its tendency to cause chronic infections. It has been hypothesized that prior exposure to C. pneumoniae may lead to chronic infection and the development of associated chronic cardiopulmonary disease. Few studies have so far addressed the occurrence of chlamydial antibodies in an elderly, unselected population. This information is important for the development of possible treatment strategies. Chlamydial antibodies were analysed from 1179 serum samples obtained from 481 men and 698 women, aged 64 y and over, who participated in an epidemiological survey carried out in a Finnish rural district. Specific IgG and IgA antibodies were measured by the microimmunofluorescence (micro-IF) test. The criterion for seropositivity was defined as a titre of > or =32 for both IgG and IgA, independently of each other. C. pneumoniae IgG antibodies occurred in 91% of the men and 75% of the women. The respective figures for C. pneumoniae IgA antibodies were 57% and 28%. The geometric mean titres (GMT) rose with increasing age and were higher in men than in women. The prevalences of C. trachomatis IgG antibodies were 13% in men and 18% in women, and for IgA antibodies, 2% and 1%, respectively. C. psittaci antibodies were rare. Only 3% of the men and women were IgG seropositive, whereas the respective figures for IgA seropositivity were 0.4% and 0.1%. C. pneumoniae antibodies indicative of recurrent or chronic infection were common in the elderly. The geometric mean titres correlated positively with age and were higher in men than in women. Other chlamydial antibodies occurred in low titres.