Simple skin fluorescence measurement, a biomarker of ageing, to identify patients of risk

Objective: Whereas patient's age is a risk factor in cardiac surgery per se, the biological age seems to be more important. Protein glycation is a major mechanism of ageing producing advanced glycation endproducts (AGEs). The accumulation of AGEs analysed by skin fluorescence (a measurement for the biological age), was tested as an outcome predictor in cardiac surgery.

Methods: 360 patients (mean age 67.2±8.7 years) undergoing cardiac surgery were analysed. We measured AGEs associated skin fluorescence and divided the subjects according their fluorescence in three groups. The group with the highest and lowest fluorescence level were compared with respect to a combined in-hospital outcome including mortality, MODS, stroke, myocardial infarction, acute renal failure, infection, low cardiac output syndrome and peripheral circulatory failure. For continuous variables, the differences between two groups were evaluated with an unpaired T-test or the Mann-Whitney U test, as appropriate. Categorical variables were analyzed by a CHI-2 test. Two-tailed P<0.05 was considered statistically significant.

Results: Patients with high (N=120) in comparison to low (N=120) skin fluorescence are significantly older (68.43 vs. 65.38 y, p=0.09), have preoperative more diabetes (28/120 vs. 5/120, p<0.001), kidney insufficiency (2/120 vs. 26/120, p<0.001) as well as cerebrovascular diseases 10/120 vs. 33/120, p<0.001). Compared to the low-fluorescence group, they have regarding the clinical outcome significantly more in-hospital events within the combined endpoint (35/120 vs. 17/120, p=0.005, ODDS Ratio 2.49).

Conclusions: Skin fluorescence measurement is an easy accessible biomarker of ageing, which can identify patients at risk.