I take it in the morning just because I found that taking it late at night harmed my sleep. I have no idea how much people taking it later in the day might reduce benefits by damaging sleep; I would guess that the elderly people usually enrolled in these trials would be taking it as part of their breakfast regimen of pills/​prescriptions and so the underestimate of benefits is not that serious.
I take it in the morning just because I found that taking it late at night harmed my sleep. I have no idea how much people taking it later in the day might reduce benefits by damaging sleep; I would guess that the elderly people usually enrolled in these trials would be taking it as part of their breakfast regimen of pills/​prescriptions and so the underestimate of benefits is not that serious.