Table 2. Samples used in multivariable linear regression analysis and prediction modelling.

DNA source	Sample number/sex	Mean age	Training set			Testing set
			Sample number	Age range		Sample number	Age range
Blood	160/80:80	40.2±22.7	112	1-75		48	1-75
Buccal cells	160/80:80	40.5±22.8	112a	2-80		48	2-80
Bones	161/129:32	46.1±14.8	112a	19-93		49b	22-75

^abecause of the missing data for PDE4C C5 or ELOVL2 C2 one sample from the buccal cell training set and one sample from the bone training set were excluded and therefore the final number of samples to train the models was 111.

^bthree samples had missing data in ELOVL2 C2.