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Gene Therapy Extends Mouse Lifespan
Grond writes "ScienceDaily reports, 'Researchers at the Spanish National Cancer Research Centre have demonstrated that the mouse lifespan can be extended by the application in adult life of a single treatment acting directly on the animal's genes. Mice treated at the age of one lived longer by 24% on average (PDF), and those treated at the age of two, by 13%. The therapy, furthermore, produced an appreciable improvement in the animals' health, delaying the onset of age-related diseases — like osteoporosis and insulin resistance — and achieving improved readings on aging indicators like neuromuscular coordination.' Notably, the therapy did not cause an increase in the incidence of cancer."
They report no statistical increase in cancer, but an absence of signal is not a signal of absence, and the methods alone should clue you in.
I guess my tolerance for cute sayings as explanations has declined as my crotchetiness has increased. The phrase you are looking for is "small sample size". Glancing at the rear of the article:
Separate groups of mice were tail-vein injected with 2*10^12 (viral genomes)/animal of either AAV9-GFP, AAV9-mTERT or AAV9-mTERTDN, a catalytically inactive form of mTERT (Sachsinger et al, 2001), at 420 days (AAV9-GFP, n=14 [50% males and 50% females]; AAV9- mTERT, n=21 [52% males and 48% females]; AAV9-mTERT-DN, n=17 [53% males and 47% females]) or either AAV9-GFP and AAV9- mTERT 720 days (AAV9-GFP, n=14 [58% males and 42% females]; AAV9-mTERT, n=23 [52% males and 48% females] of age. All mice are of a >95% C57BL6 background. Longevity comparisons were always made within the same mouse cohort to avoid minimal possible differences in genetic background between the groups.
They had five samples from 14 to 23 in size. That's a bit slim for some of the claims they make such as the bit about cancer.