The reduction of Total Solar Irradiance estimated over the 22th, 23th and 24th solar cycles implies a decline in solar forcing. This long-term trend is valid during the SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric ChartographY) operation time as well. We retrieved atomic oxygen concentration ([O]) profiles with help of SCIAMACHY observations of the nightglow green line emission . We quantified the sensitivity of equatorial [O] to the 11-year and 27-day solar cycle forcing represented by such proxy indicators of solar activity as MgII index and Lyman-alpha with help of the wavelet, cross-correlation, superposed epoch, linear regression and multiple-linear regression analysis methods. However, the linear trend in [O] values estimated with help of the multiple-linear regression for the years 2003 – 2011 is positive, and not significant. The linear trend in [O] values averaged in the altitude interval 90 km – 100 km is equal to 0.09(30)% with the 68% confidence level of the sensitivity based on MgII index and 0.36(34)% in the case of Lyman-alpha. We identified an 11- year solar cycle variation, quasi-biennial and annual/semi-annual oscillations as well as signatures of the 27-day cycle of solar activity as presented in the MLT O layer. The most remarkable result is that the found sensitivities to the 11-year and 27-day solar cycle agree with each other within their uncertainties. The sensitivities to the 11-year solar cycle do not depend on the kind of temporal (annual or monthly) averaging of the [O] time series, but depend on its spatial (altitudinal) averaging.