Oragene og 500 collection kit

DNA was isolated from saliva samples from 389 participants following the protocol from Oragene OG500 collection kit (DNA Genotek, Ottawa, Ontario, Canada). DNA concentration was determined by Qubit fluorometry (ThermoFisher Scientific, Waltham, MA, USA). Average telomere length was measured using an adaptation of qPCR methods (Drury et al., 2014 (link)). 33 ng of DNA was used for each assay containing 1X Power SYBR green (Applied Biosystems, Foster City, CA, USA) and 900 nM forward and reverse telomere (T) or 600 nM forward and reverse single copy albumin gene (S) primers (Table 1). Within a single experimental plate, all samples were run in triplicate for telomere and albumin reactions and cycle threshold (C_T) values for each sample for each gene were averaged. All experimental plates were also run in duplicate with sample positions reversed. Individual samples were required to have an inter-plate coefficient of variation (CV) below 0.6. The geometric mean of all CV values for sample reactions on duplicate plates was required to be below 0.1 (Drury et al., 2014 (link)) . T/S Ratio was calculated using the ΔC_T method as $2^{-\left[C_t\left(T\right)-C_t\left(S\right)\right]}$ .