Mobile phone use does not up the risk of cancer, at least in the first 10 years of use, the largest investigation to date shows. Past studies had suggested an increased risk of acoustic neuroma - a tumour of the nerve connecting the ear and the brain - but others did not.
http://news.bbc.co.uk/2/hi/health/4196762.stm ------------------------------------------------------------------------------------------------------------------------------
What is the meaning of 'does up the risk' here? Does it means enhances the risk of getting something?
I haven't learn to write like this.
The other question is on the words 'had suggested'.
I think it should be fine to write 'Past studies suggested an increased risk of .............
Is it necessary to write the past perfect here?