The findings were based on participation, online and problem gambling surveys, based on 1,000 telephone surveys conducted per quarter, 2,000 online surveys conducted per quarter and screen scoring for problem gambling.
The overall participation figure for any gambling activity was 45%, down from 53% a year earlier.
A total of 49% of males participated in any gambling activity in the period, down from 57%, and the female figure was 41%, down from 50%, with the gender split of the respondents being virtually 50/50 (1,950 male and 2,050 female).
UKGC put the decline partially down to falling numbers of UK National Lottery players, with the totals being 27% for overall (-6%), 30% for males (-6%) and 25% for females (-6%) when excluding the National Lottery.
Despite the fact that the 45-54 year-old age bracket scored highest in participation rates with 54%, it was the third consecutive year that the total had dropped for that age bracket, falling from 55% in 2014.
The 18-24 age bracket scored the lowest with 33%, down from 51%.
Those figures were for overall gambling, and for online, the 45-54 and 35-44 age brackets tied for first with 21% participation rates, both minor increases.
The online investigation showed that 33% of online gamblers use a mobile/tablet to gamble and players in the 25-34 age bracket were the most likely to do so (50%).
With problem gambling, a total of 0.5% of respondents were problem gamblers, flat-lining with the previous two years, with 18-24 year-old being the most likely to be problem gamblers, scoring 1.1%.
Horse racing was found to be the event with the highest betting-participation rate with 4%, down from 6%.
