14 or less: Characters this young do not appear on-screen in my campaigns.
17 or less: -1 Strength, Intelligence, Wisdom, and Charisma.
18 to 35: No modifiers. If for some reason a character started younger than 18, remove the above penalties.
36 to 50: -1 Con & Dex. +1 Intelligence & Wisdom.
51-60: -1 Con, Dex, & Str. +1 Wisdom & Charisma.
61-70: -1 Con, Dex, & Str.
71-80: -1 Con, Dex, & Str.
80+: Knock off a point of a randomly-selected attribute every year until one attribute is reduced to zero and they die.
A few notes:
PCs may not select the age they start, out of some kind of bid to get bonuses to mental attributes. The starting campaign age is defined randomly as in my prior post. Penalties accrue according to biological age, bonuses accrue according to chronological age. Thus, a character who begins taking anagathics at the age of 21 will have all the mental attribute bonuses before they ever suffer any negative aging effects. All changes after the age of 35 are cumulative. Attributes should probably be capped at 18, unless the GM wants to consider the effects of moderately superhuman mental capabilities.
The preceding are written for use by PCs, who I assume have healthy and active lives rather than sitting around watching TV and eating potato chips, and who access excellent medical care when needed. The GM is encouraged to do whatever they want with NPCs, who may not age as well. PCs who attempt to live on planets of lower tech-levels without access to TL4 medical care may suffer more serious problems than attribute penalties in their seventies and eighties.
The other prong of life extension is the rejuvenation treatment. This is available at only a handful of clinics in the Nyx Cluster, and the actual details of the treatment are kept completely secret. The patient is kept under sedation for long periods over the course of a month or two of treatment, and have very little knowledge of what is actually done to them.
Access to the procedure is equally strictly controlled by the government, the State, and the Academe. A prospective patient is advised to be in good standing with the powers that be (a bit of status ala the Reputation Economy in Transhuman Tech is advisable!) and to have 4MCr in ready cash.
Any given patient can only undergo rejuvenation treatment once. This is a matter of the procedure failing rather than unwillingness on the part of the clinic's sponsors. It simply knocks 40 years off the patient's biological age, removing any accrued penalties and restoring them to the image of youthful health and vigor. At the time of treatment, the GM should roll 1d6+20. That is the minimum biological age to which the patient will be reduced to. There is little point in attempting rejuvenation treatment until one feels the enervating effects of age.
Rejuvenation treatment is completely compatible with anagathics. A person who starts taking anagathics young and keeps them up throughout the entire course of their life (they have no effect before the patient reaches their early twenties), receives a rejuvenation treatment in their late sixties, and then continues to take angathics...that person could enjoy a very long and healthy life.
Of course, doing so represents an expense beyond the dreams of the typical citizen of the State, and also requires substantial service to hegemonic extraplanetary powers.