The details are in the article, but to summarise, this was a 6-year follow-up study of 2246 older diabetics who had no signs of dementia at the start. In subjects with a raised HbA1c level (glycosylated hemoglobin, a measure of long-term average blood glucose) at the outset, a reduction of 10 per cent or more after 1 year was associated with an increase in the risk of developing dementia by year 6, whereas a reduction of  HbA1c of only 5-10 per cent was not. Importantly, this was not due to any severe attacks of low blood glucose or other health problems having occurred during the follow-up period.