Lipofuscin in saliva and plasma and its association with age in healthy adults

To compare blood and salivary levels of lipofuscin in healthy adults and to analyze the relationship between the lipofuscin level and the healthy adults' age. One hundred and twenty-two healthy volunteers were recruited and divided into three groups according to their age: young (n = 42, 20-44 years old), middle-aged (n = 51, 45-59 years old), and elderly (n = 29, 60-74 years old). One ml saliva and 5 ml whole blood were collected from each person. An ELISA kit was used to measure both the plasma and salivary lipofuscin levels. The differences between the groups were compared with independent-sample t test, and the relationship between the salivary lipofuscin level and the age was assessed with linear regression analysis. The mean +/- A SD of the lipofuscin level in the saliva and plasma of 122 subjects was 68.93 +/- A 1.32 and 78.05 +/- A 1.75 mu mol/l, respectively. No gender-dependent differences were observed in either the salivary or the plasma lipofuscin level (saliva: p = 0.443, plasma: p = 0.459). The salivary and plasma lipofuscin levels of the elderly subjects were significantly higher than those of the young (saliva: 80.72 +/- A 13.53 mmol/l versus 59.12 +/- A 1.92 mmol/l, p = 0.0003; plasma: 93.31 +/- A 3.14 mmol/l versus 67.43 +/- A 2.54 mmol/l, p = 0.0002) and middle-aged (saliva: 80.72 +/- A 13.53 mmol/l versus 70.31 +/- A 11.17 mmol/l, p = 0.0004; plasma: 93.31 +/- A 3.14 mmol/l versus 78.12 +/- A 2.40 mmol/l, p = 0.0002) subjects. Similarly, the salivary and plasma lipofuscin levels of the middle-aged subjects were significantly higher than those of the young subjects (saliva: 70.31 +/- A 11.17 mmol/l versus 59.12 +/- A 1.92 mmol/l, p < 0.0001; plasma: 78.12 +/- A 2.40 mmol/l versus 67.43 +/- A 2.54 mmol/l, p = 0.0019). The lipofuscin levels in the saliva and plasma were significantly positively correlated with the subject age (r = 0.551, p = 0.0001; r = 0.528, p < 0.0001). Furthermore, the salivary lipofuscin level and plasma lipofuscin level also were found to have a positive correlation (r = 0.621, p < 0.0001). No gender-dependent differences were observed in either the salivary or plasma lipofuscin levels. The salivary and plasma lipofuscin levels were positively correlated, and the age is positively correlated with lipofuscin content in saliva.