  Current precision big bang nucleosynthesis (BBN) studies motivate us to
revisit the neutron lifespan in the plasma medium of the early universe. The
mechanism we explore is the Fermi-blocking of decay electrons and neutrinos by
plasma. As result, neutrons live longer and we find a significant 6.4\%
modification of neutron abundance in the BBN era arising from in plasma
modification of the neutron lifetime. This effect can influence the final
abundances of the light elements in BBN.
