Conover and Bale (2007) suggested that the control of the availability of IGF-1 at local, tissue level and the moderate reduction rather than the complete inhibition of IGF-1 signaling is the key to lifespan extension. Survival data collected in the PAPPA-/- mice study showed that the knockouts experienced a reduction in age-related degenerative diseases and displayed a lifespan extension of about 30%, with degenerative diseases being the cause of high mortality in wild type mice (Conover and Bale, 2007). This evidence concerns the gene IGF1 and neurodegenerative disease.