More than half of viewers (55 per cent) believed there was excessive violence five years ago, but that figure has fallen to 35 per cent.
Those who think there is too much sex is down from 35 per cent to 26 over the same period, while swearing is a concern for 35 per cent, down from 53.
Ofcom said a change in attitudes among older viewers is one of the reasons for the figures for sex, violence and swearing dropping markedly.
Awareness of the TV watershed - established 50 years ago this month to protect children from unsuitable scenes before 9pm - is 94 per cent, up from 91 per cent five years earlier.
Ofcom said on-demand and catch-up viewing would prove a "new challenge" in terms of protecting children using the watershed concept, but such services currently account for 2.5% of viewing.