We report the latest study of the UVS/Voyager 1 Lyman α data obtained between 1993 and 2003. These data show that the radial variation of the intensities measured close to the upwind direction has changed abruptly at the end of 1997 when the spacecraft was at a distance larger than 70 AU from the Sun. The coefficient α of the power law describing the intensity as a function of solar distance has changed from a value of -1.58 ¿ 0.02 between 1993 to 1997 to a value of -0.22 ¿ 0.07 after 1998. This change is not compatible with current stationary models of the hydrogen distribution whether they include the effects of the heliospheric interface or not. We discuss possible causes for this change including temporal variations of the hydrogen distribution near the heliopause.