Skin aging has been shown to result from a combination of the effects of chronological factors (intrinsic aging) and of environmental ones (extrinsic aging).
This search used the broad definition of 50+ as used by the World Health Organisation [ 20], both to maximise the potential literature found and to acknowledge that socially constructed concepts of age often include biological as well as chronological factors.
Dependent variables (weight, height, body mass, BMI, and body fat percentage) were compared between boys and girls using analysis of variance with two factors (gender and age; as biological and chronological factors, respectively), followed by Bonferroni's multiple comparison test [ 18].
B = unstandardised regression coefficients, β = standardised regression coefficients, sr2 = semipartial correlations Given the chronological time factor in which the variables were assessed, a hierarchical regression was performed where antenatal factors were entered followed by the postnatal variable parenting stress.
With increasing chronological age, these factors may influence performance more than biological risk factors [ 48, 51].
We can speculate that as chronological age increases, factors other than age become more important in determining the rate at which NGFs are lost through apoptosis.
In addition to intrinsic genetic factors, chronological aging is controlled through epigenetic mechanisms and is affected by environmental parameters including nutrition [4], which clearly leads to consider this biological process as a complex multifactorial phenomenon.
Association tests were performed using the linear mixed models defined in Box 1: between each pathway factor and chronological age and between single genes and chronological age.
They suggest that, in addition to its role in replicative aging in budding yeast, replication stress is an important factor determining chronological lifespan in this organism.
Although replication stress-induced recombination in the rDNA locus is a major determinant of budding yeast replicative lifespan ([13] and references therein), replication stress has not been considered a factor in chronological aging in this organism.
Our findings point to an efficient Rim15-dependent growth arrest in G1 that also requires downregulation of Cln3 as an additional factor determining chronological lifespan in this organism (Fig. 6A).
