i don't think anyone has done that research yet, g.
i would imagine that having optimal D3 status must be better than having suboptimal D3 status, regardless of age.
studies on D3 and MS:
odd sx? no dx? check w/ dietitian
DRI=MINIMUM eg bit.ly/1vgQclQ
99% don't meet these. meds/lifestyle can affect levels
status can be low in ms & other cond'ns
'but my results are normal'. typical panels don't test all
deficits occur in 'normal' range