Table 1.
Biomarkers of aging, methods of measurement and the impact of aging.
| Anatomical site | Parameter | Method of measurement | Age-related changes |
|---|---|---|---|
| Peripheral blood leukocytes | Telomere length (TL) | qPCR | TL shortens |
| CDKN2A expression | qRT-PCR to estimate mRNA levels | Increased expression | |
| Corneal endothelium | Endothelial cell density (ECD) | Specular microscopy | Decreased ECD |
| Coefficient of variation (CV) | Increased CV | ||
| Hexagonality index (Ex) | Decreased Ex | ||
| Lens | Lens opacity | Pentacam – lens densitometry | All increase |
| Linear value | |||
| Peak | |||
| 3D average | |||
| Retina | Retinal nerve fibre layer (RNFL) thickness (average, superior, inferior, nasal, temporal quadrants) | Optical coherence tomography (OCT) | Thinner RNFL – all quadrants |
| Retinal vessel calibre | Semi-automated retinal analysis software applied to fundus photographs | Reduced diameter of arterioles and arterio-venous ratio (AVR) | |
| Systemic | Frailty status | Assessment of walking speed, grip strength, self-report of weight loss, exhaustion and low physical activity | Frailty status increases |
| Non-frail (no criteria) | |||
| Pre-frail (1–2 criteria) | |||
| Frail: ≥3 of 5 criteria | |||