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Table 1 Individual biomarkers used to compose the frailty indices (FI-B). The cut off points were defined to achieve the best separation of survival curves between people with and without the deficit and minimizing the P value of the log rank test

From: Age-related frailty and its association with biological markers of ageing

Biomarker Cut off point Direction of risk Number of participants P value**
At lower risk At higher risk
Inflammation*
Cytomegalovirus serology (IgG) Positive 108 641 0.327
High sensitivity C-reactive protein (mg/L) >25 High 737 37 <0.001
IL-6, basal (pg/mL) >15 High 27 676 0.399
IL-6, post-stimulation (pg/mL) >1100 High 176 527 0.92
TNF-alpha, basal (pg/mL) <95 Low 55 637 0.646
TNF-alpha, post-stimulation (pg/mL) >80 High 60 643 0.116
Leptin (ng/mL) <40 Low 214 495 0.023
Adiponectin (μg/mL) >20 High 657 83 0.012
Homocysteine (μmol/L) >30 High 422 35 0.006
Albumin (g/L) <40 Low 365 397 <0.001
Haematological
Haemoglobin (g/dL) <11 Low 676 76 <0.001
Platelets (×109/L) <170 Low 675 73 0.003
White blood cells (×109/L) >7 High 470 274 0.035
Neutrophils (×109/L) >7 High 715 29 0.007
Lymphocytes (×109/L) <1.5 Low 530 214 0.028
Monocytes (×109/L) >0.75 High 639 105 0.14
Basophils (×109/L) <0.06 Low 156 588 0.156
Eosinophils (×109/L) >0.5 High 688 56 0.15
Immunosenescence
CD4 T cells (% T cells) <44 Low 345 367 0.029
CD8 T cells (% T cells) >35 High 579 128 0.015
CD8 TEMRA T cells (% CD8 T cells) >0.6 High 672 36 0.014
Senescent Memory CD4 T cells (% Memory CD4 T cells) >70 High 618 93 0.079
Memory CD4 T cells (% CD4 T cells) >35 High 672 43 0.057
CD4/CD8 T cell ratio <0.6 Low 662 31 0.005
Memory/naïve CD4 T cell ratio >3.3 High 692 20 0.034
Memory/naïve CD8 T cell ratio >15 High 677 20 0.352
Memory/naïve B cell ratio >2.5 High 652 36 0.026
Cellular ageing/Oxidative stress
Telomere length (bp) <3000 Low 634 66 0.118
DNA repair (%) <20 Low 589 156 0.078
DNA damage/DNA repair ratio >6.5 High 688 44 0.063
TGF beta, transforming growth factor beta (ng/mL) <20 Low 102 644 0.003
IGFBP1, insulin-like growth factor-binding protein 1 (ng/mL) >150 High 574 162 0.001
IGFBP3, insulin-like growth factor-binding protein 3 (ng/mL) <800 Low 92 652 0.357
iPF2alpha-III (LC/MS/MS) (ng/mL) <4.5 Low 85 629 0.053
iPF2alpha-VI (LC/MS/MS) (ng/mL) <4 Low 423 291 0.1
iPF2alpha-III (AutoDELFIA) (ng/mL) <0.6 Low 512 103 0.258
Genetic/Epigenetic
Mitochondrial DNA haplogroup X, I, heteroplasmic 675 30 0.031
APOE genotype E4 454 167 0.024
CPG island DNA methylation (%) >7 High 28 451 0.67
Line1 DNA methylation, surrogate for genome-wide DNA methylation (%) >80 High 73 197 0.63
  1. *The recorded cytokine levels may be perceived as higher than usual. Because we wanted to measure basal and post-stimulated cytokines, we measured cytokines in non-coagulated LiHe blood, using blood supernatants, not serum. Furthermore, we used an electrochemiluminescent method (MSD technology) that in our hands is much more sensitive than standard ELISA assays. Both factors are likely to explain our observed cytokine levels
  2. **Statistically significant P-values (≤0.05) are shown in bold