Character Age, Aging, Disease, and Death
Character Age (p.12) 
The vanilla DMG age tables apply for playable races present in Oath-Bound. Gnomes, half-elves, half-orcs, and lizardmen are not playable in Oath-Bound and their entries do not apply. Race-specific lifespan variations are addressed in the relevant race documentation.
Aging (p.13) 
The vanilla DMG aging tables apply for playable races present in Oath-Bound. As with Character Age, entries for absent races do not apply.
Disease (p.13) 
This section applies in Oath-Bound as written in the DMG. The mitigating properties of herbs and folk medicine may reduce the severity or duration of disease in ways consistent with the herb model — they do not cure. See Value and Reputed Properties of Gems, Herbs, etc.