You're just looking at statistical noise.

By pure chance you expect ~5% of studies to show with a 95% confidence level that radiowaves cause cancer/alzheimer's and ~5% to show with a 95% confidence level that mobile phones prevent cancer/alzheimer's. If you aggregate a large number of studies of high quality(e.g. you can verify that there is no publishing bias, that the article would have been published no matter its results) you find no statistically significant causal link between microwave use and cancer. cellphone use and cancer, powerlines and cancer, radiotowers and cancer etc.

Radiowaves and microwaves across the entire spectrum have been investigated for safety over 60 years now; there is no plausible mechanism for them to do more than heat flesh(stay out of high intensity fields), just give it up already.

Would it increase or reduce chances of cancer?

"Vascular dementia is the second most common form of dementia after Alzheimer's disease" ...

"There appeared to be no link either way between vascular dementia and cancer."

... which might explain why mobiles could prevent Alzheimer's disease:

http://www.healthscout.com/news/1/634268/main.html