Trends of mean winds and waves are studied on the basis of continuous wind measurements in the mesosphere and lower thermosphere (MLT) using MF and Meteor radars since 1998 at Andenes (69°N, 16°E), and since 1990 at Juliusruh (55°N, 13°E). At middle latitudes, trends of zonal winds between1990 – 2015 show a significant increase of westward directed winds in summer below 83 km. In winter, the trends are nearly opposite, however, the results are only partly significant due to the higher variability of planetary waves. At polar latitudes, the seasonal variation of the zonal wind is dominated by a stable, but in comparison to middle latitudes weaker westward directed jet below about 88 km in summer. The trends are only partly significant and show an increase of westward directed winds at all heights. Possible differences caused by both used radar techniques will be discussed. The long term wind measurements are also used to estimate trends of the activity of gravity waves (GW) with different periods. We will update our previous results indicating that the observed zonal wind trend at about 75 km during summer at mid latitudes goes along with an enhanced GW activity with periods of 3 - 6 h thus illuminating the contribution of the selective GW filtering by the background winds. These studies are extended for other periods and seasons at both latitudes. In contrast to trends at mid latitudes, the filtering effect seems to be of less importance at polar latitudes during the summer months.