Association between C-reactive protein, neutrophils, lymphocytes, cognition, and functional capacity in an oldest old population

Abstract

Systemic inflammatory processes can cause changes in cognition and functional capacity in the general population. Currently there are no accessible biomarkers capable of early detection and monitoring of such pathologies, and only few studies involving older than 80 years-old population were done. The C-reactive protein (CRP) and blood counts are low-cost tests that are often performed in routine basis. From the blood counts it is possible to evaluate the absolute count of neutrophils and lymphocytes, which are peripheral blood inflammatory markers. With these results, it is also possible to evaluate the neutrophils to lymphocytes ratio (NLR). Therefore, these tests may be potential biomarkers in the evaluation of the development of dementia, mild cognitive disorder, and functional dependence, with the possibility of assisting in the clinical management and prevention of such pathologies.

Objective

To evaluate the association between cognition and functional capacity with C-reactive protein, absolute neutrophil count, lymphocyte count, and NLR in a population of elderly people aged 80 years and older.

Methods

Observational analytical cross-sectional study conducted in the cohort of the Longevous Project of the Discipline of Geriatrics and Gerontology of UNIFESP. Complete blood counts (CBC) and CRP were collected from 244 patients included in the study between 2010 and 2013. Gender and the presence of hypertension and diabetes mellitus were also characterized. Associations between the absolute values of neutrophils and lymphocytes and the NLR with cognitive tests (mini mental state examination, MMSE, and clock drawing test, CDT) and with functional capacity (basic activities of daily living, BADL or Katz score, and instrumental activities of daily living, IADL or Lawton score) were performed using nonparametric Mann-Whitney and Kruskall-Wallis statistical tests.

Results

We found no associations between the markers obtained by the CBC and the cognitive assessment tests. We also found no association between the CRP and the MMSE. However, we obtained a statistically significant difference between the CRP marker and the CDT, with P = 0.003. There was no statistically significant difference between markers obtained by CBC or CRP with the BADLs. But we observed a statistically significant association between the IADLs and the absolute count of neutrophils and lymphocytes, respectively P = 0.0379 and 0.0190.

Conclusion

The presented results contribute to the hypothesis that serum inflammatory biomarkers can be useful in the assessment of health outcomes. We identified that patients with lower functional capacity for IADLs have higher absolute neutrophil and lymphocyte counts when compared to patients with higher functional capacity. In addition, we identified that patients with low performance on CDT have CRP at higher levels when compared to patients with higher cognitive ability. Our results suggest that markers of inflammation easily obtainable through CBC and CRP may be useful for monitoring the functional and cognitive ability of long-lived people.