Toxoplasmosis intensity has been linked to senile infirmity
Researchers from four countries have found an association between toxoplasma antibody levels and frailty and signs of persistent inflammation in the elderly. The paper is published in The Journals of Gerontology: Series A.
The increasing global aging of the population requires consideration not only of concepts such as chronological and biological age, but also of individual sensitivity to pathophysiologic problems. One of its indicators is infirmity (senile asthenia, decrepitude), a multifactorial syndrome associated with a decrease in physiologic reserves and resistance to stressors. Biological mechanisms of its development include vascular endothelial dysfunction and inflammation - persistent inflammation in the absence of infections.
The feline parasitic protist toxoplasma protist (Toxoplasma gondii) readily infects humans and is widespread in the human population. With normal immunity, its presence in the body often passes without visible symptoms, but epidemiologically it is associated with increased allostatic load, a known risk factor for senile infirmity.
To test the possible role of toxoplasmosis in the development of frailty, Hira Mohyuddin of the University of Maryland and colleagues from Austria, Spain, Portugal, and the United States conducted a secondary cross-sectional analysis of data and blood plasma samples from 601 participants in three Spanish and one Portuguese cohort. Their ages at the time of inclusion ranged from 65-102 (mean 77.3) years; 61 percent were women.
Plasma samples were subjected to qualitative and quantitative enzyme immunoassay for immunoglobulin G (IgG) to toxoplasma (an indicator of the presence and intensity of chronic infection). It also determined various biomarkers of immune status and inflammation, including inflammation: kynurenine, tryptophan and their ratio, neopterin, interleukin-6, tumor necrosis factor alpha and its soluble type 2 receptor (sTNF-RII). Senile infirmity was assessed using Fried criteria. Demographic data, level of depression according to the GDS scale, cognitive function according to the MMSE method, and comorbidities according to the CCI score were considered as cofactors. Statistical analysis was performed using multivariable logistic regression.
Antibodies to toxoplasma were detected in 67 percent of participants. Their serointensity (logarithmic titer of IgG concentration) was significantly higher in people meeting the criteria for senile infirmity (p = 0.0005). The association with seropositivity (the fact of having IgG) was generally statistically insignificant (odds ratio 0.84; 95% confidence interval 0.45-1.54; p = 0.56), but was clearly seen among depressed patients (odds ratio 0.21; 95 percent confidence interval 0.06-0.75; p = 0.016) and people with only basic education (odds ratio 0.37; 95 percent confidence interval 0.16-0.86; p = 0.021). Of the biomarkers associated with frailty, levels of kynurenine/tryptophan ratio and sTNF-RII were positively correlated with serointensity to toxoplasma (p < 0.05), but not the other indicators studied.
As the authors of the paper note, they were able to demonstrate for the first time a direct link between chronic T. gondii infection and senile frailty,. However, the study has limitations in the form of a cross-sectional design, and the results require replication in other papers. Some biomarkers of inflammation have been shown to be associated with both toxoplasmosis and frailty, but they do not fully mediate the association between these conditions.