That's probably something to do with Wikipedia's editing guidelines these days. They have a rule against using primary research citations. Only literature reviews, books, and other secondary sources are acceptable.
I found the original source for the claim, which may be no better for supporting the claim for a number of reasons (why has this not been replicated, or did replication fail?):
http://www.sciencedirect.com/science/article/pii/05315565739...
Effect of dimethylaminoethyl p-chlorophenoxyacetate on the lifespan of male Swiss Webster albino mice, J Exp Gerontol 8: 177, 1973
Author: R. Hochschild of "Microware Instruments Co" of California.
doi (for sci-hub): 10.1016/0531-5565(73)90024-7
http://www.sciencedirect.com/science/article/pii/05315565739...
Note: If anyone is actually interested in the field of biogerontology, I recommend following the https://www.fightaging.org blog for editorialisation of news and research papers coming out of the field.