I scanned the article. The authors make no claim that they reversed a year of cognitive decline. Nor did they assess the health of the subjects at any earlier date in order to compare post-treatment performance to that pre-treatment performance to quantify the treatment effect.
At most, they idly speculate that on one metric, ONLY THE RESPONDING AD PATIENTS saw as much as 15 months of disease regression (ADAS-cog):
"Since a typical decline in ADAS-cog expected for AD subjects is around 4 points over a 12- to 15-month period [48], 2 months of TEMT appears to have reversed cognitive decline (as measured by the ADAS-cog) of responding AD subjects as a group, perhaps back to the cognitive level subjects had 12 to 15 months earlier."
At most, they idly speculate that on one metric, ONLY THE RESPONDING AD PATIENTS saw as much as 15 months of disease regression (ADAS-cog):
"Since a typical decline in ADAS-cog expected for AD subjects is around 4 points over a 12- to 15-month period [48], 2 months of TEMT appears to have reversed cognitive decline (as measured by the ADAS-cog) of responding AD subjects as a group, perhaps back to the cognitive level subjects had 12 to 15 months earlier."
Science Alert clearly hyped the story's lead.