I would be curious as to how they are measuring the subject's perception of their age. Are they just asking them how old they feel? How do they get meaningful results?
> Subjective age was assessed using a single-item question: ‘On some days you may feel older or younger than your calendar age. What age do you feel right now?
How would any of these people _know_ what older actually "feels like?" It's hard to believe they felt this surrogate question would reveal anything useful, let alone, that the numeric values associated with it were worth averaging.
Good point. The study would be better if they tracked actual biomarkers like HRV, RHR, blood pressure, etc. rather than asking the question, how old do you feel.