Dear Life Extensioner,

If you are preparing/analyzing a lifespan extension study,
please feel free to ask for further statistics It is rather unusual to start lifespan experiments with animals that are already aged. We wanted to start treatment (...) when the rate of 'natural death' becomes signifiant in C57BL/6 laboratory male mice.

Starting with mice that are too old would imply that selection by death has comenced and that only resistant mice are being studied.

If the mice are too young then in the short term no natural death will occur and any survival improvement due to a therapy may not be detected. Hi everyone, 

I would like to suggest to the community a simple but possibly fruitful concept for anti-aging interventions: 
STARTING LIFESPAN EXTENSION TESTS WITH OLD ANIMALS 

I clearly see 3 major benefits: 

1. Adequacy for anti-aging interventions destined to adults/aged persons. 
2. Possibility to see short-term positive effects 
3. Gain of time 
Concerning your points about late-onset studies, you are absolutely right -- and indeed I think most gerontologists privately agree with you (...)

a successful postponement of aging with a treatment started late in life will always stimulate much more self-interest from the general public, leading eventually to increased funding, than something done in the germ line or begun at weaning. LOLES = Late Onset Lifespan Studies:
more adequate, safer, faster, less expensive