Chlamydia pneumoniae May Be a Risk Factor for Multiple Sclerosis

There is a significant positive relationship between Chlamydia pneumoniae infection and the development of multiple sclerosis.

There is a positive association between Chlamydia pneumoniae (Cpn) and multiple sclerosis (MS), according to study findings in published in the journal Multiple Sclerosis and Related Disorders.

There are many genetic and environmental factors that can lead to the formation and progression of MS. Previous studies have shown conflicting information regarding the effects of Cpn in the progression of MS. Researchers conducted a meta-analysis to determine the extent of the involvement of Cpn in MS development and progression.

Data was collected from PubMed, Embase, Scopus, and Web of Science databases. There were 1472 studies identified and after exclusion, 37 studies with 51 datasets remained in the analysis. The researchers collected studies and divided them into polymerase chain reaction (PCR) based datasets (n=26) and serological-based datasets (n=25). 

All the studies included in the analysis were published from 1999 to 2015. Of these studies, 21 had a comparative cross-sectional design, 23 used cerebrospinal fluid (CSF) samples to confirm a diagnosis of Cpn infection, and 3 used serum samples to confirm Cpn.  

The researchers analyzed 1094 experimental group and 1076 control group participants using PCR.

These results confirm previous evidence suggesting that Cpn infection could be a potential risk factor for MS development.

The prevalence of Cpn was 32.67% (95% CI, 21.77%-43.58%) in patients with MS and 7.58% (95% CI, 5.01%-10.15%) in the control group. 

In the PCR-based dataset, the random-effects meta-analysis model (REM) revealed a significant association between Cpn infection and MS development (odds ratio [OR], 5.29; 95% CI, 3.12-8.97). However, there was no significant association in the serological-based datasets (OR, 1.34; 95% CI, 0.88-2.03). 

In the subgroup analyses of the PCR-based datasets, there was a significant association between Cpn infection and MS development observed for CSF (OR, 5.70; 95% CI, 3.24-10.05) and serum (OR, 4.84; 95% CI, 1.44-16.21) samples. Additionally, significant associations were observed for all control group patients, whether they were healthy (OR, 16.11; 95% CI, 4.98-52.03) or hospital-based (OR, 2.88; 95% CI, 1.21-6.83) controls. 

With regard to study quality, significant associations were reported for both moderate (OR, 5.14; 95% CI, 1.39-18.98) and high (OR, 5.48; 95% CI, 3.07-9.79) quality studies.

Upon analysis of the serological-based datasets, the researchers found that only studies using CSF samples reported significant results (OR, 3.41; 95% CI, 1.19-9.75).

“Our findings indicate that an agreement among future researchers to predominantly utilize PCR-based assays on CSF fluid would diminish heterogeneity,” the researchers wrote.

Overall, the researchers concluded that “These results confirm previous evidence suggesting that Cpn infection could be a potential risk factor for MS development,” the researchers wrote.

Study limitations are the inability to agree on a gold standard diagnostic method, publication bias, and a small sample size.


Arjmandi D, Graeili Z, Mohammadi P, et al. Chlamydia pneumonia infection and risk of multiple sclerosis: a meta-analysis. Mult Scler Relat Disord. Published online June 29, 2023. doi:10.1016/j.msard.2023.104862