Some scientists have previously hypothesized the possible etiological role of Chlamydia (new name Chlamydophila) pneumoniae in the development of multiple sclerosis - a severe progressive demyelinating disease of the central nervous system causing progressive disability and death of patients. However, the results of studies on this subject were very contradictory.

Scientists at Harvard University (United States) analyzed data from two national nursing health studies (Nurses Health Study - NHS and Nurses Health Study II - NHS-II) using a design case-control study to determine the relationship between C. pneumoniae infection and the development of multiple sclerosis.

Among the 32826 and 29722 nurses examined during the NHS and NHS-II, respectively, 141 cases of diagnosis of definite or probable multiple sclerosis were identified. For each case of the disease, two "healthy" controls were selected without this disease, corresponding in age and in the same cohort of patients (NHS or NHS-II).

Infection with C. pneumoniae was determined by detection of specific antibodies - class G immunoglobulins (Ig G) against this type of chlamydia in the patient's blood serum by micro-immunofluorescence.

The study found that the presence of specific Ig G was associated with a risk of developing multiple sclerosis (odds ratio - OR = 1.7; 95% confidence interval - CI = 1.1-2, 7). These indicators did not change significantly after data were given for patients by age, heredity factors, place of birth and smoking (OS = 1.9; 95% CI = 1.1 to 3.1).

The presence of Ig G antibodies was only moderately associated with an increased risk of developing a relapsing-remitting form of multiple sclerosis (OR = 1.7; 95% CI = 0.9-3.2), but it has led to a very significant risk of developing a progressive form of this disease (OR = 7.3; 95% CI = 1.4-32.7).

The geometric mean titers of specific class Ig G antibodies against C. pneumoniae did not differ significantly in patients with the relapsing-remitting form of multiple sclerosis and in "healthy" women control group (44 vs 39), but were significantly higher in patients with an active form of the disease (99 vs 40).

The results obtained indicate that infection with C. pneumoniae is accompanied by an increased risk of developing a progressive form of multiple sclerosis.