our report from our chief science correspondent, robert bazell. >> hey, how are you doing today? >> reporter: at sip the experience coffee shop in atlanta and around the country today men were glad to hear about the new findings. >> before i thought it was really bad for your health, you know, to drink a lot of coffee. so that's good news. >> it gives me even more of an incentive to drink coffee. that's for sure. >> reporter: researchers at the harvard school of public health studied almost 48,000 men for 12 years and found that drinking up to six cups of coffee a day lowered the risk of prostate cancer. >> the strongest association was actually for prevention of advanced-stage or lethal prostate cancer. and there we found that the men who drank the most coffee had 60% lower risk of developing lethal prostate cancer during follow-up. >> reporter: surprisingly, the study found no difference between regular and decaffeinated coffee. if not caffeine what is the cause? previous research shows coffee beans contain antioxidants, anti-inflammatory compounds, and chemicals that help cont

our report from robert bazell. >> are you ready to listen? >> reporter: autism interrupts social interactions and covers a broad spectrum from terribly severe to mild. today finds the mild form might afflict many more students that assumed. the incidence of autism could be as high as 1 in 38 in children, twice as high as most previous estimates. >> autism is more common than we think, and there are a lot of kids out there who are actually doing somewhat well in mainstream schools but can do even better if they're provided some assistance. >> reporter: researchers carried out the study in a suburb of seoul, south korea. the study was easier to do there because of korea's universal health care and education. but the scientists say there's no reason to think the results would be different elsewhere. most previous research examined medical records of children whose parents sought help, but this study sponsored by "autism speaks" focused on 50,000 of the 7 to 12-year-olds in that suburb, those in regular schools as well as those in special educati

robert bazell, nbc news, sacramento. >> does it stay on better? >>> that's our broadcast for this thursday night. thank you for being here with us. i'm brian williams, and we hope to see you right back here tomorrow evening. good night. -- captions by vitac -- www.vitac.com

robert bazell has more. >>> hepatitis c is called the silent epidemic. 3/4 of those living with the liveraging virus are undiagnosed. many baby-boomers became infected decades ago. rene webb was infected more than 20 years ago from a needle stick when she was a student nurse. she learned she had hepatitis c in 2002. as a nurse, the young mother of two was worried. >> like, wow, this could be really, really ugly. >> with the only option, a grueling one-year regiment with the drugs interferon with a slim chance of a cure, she was willing to wait. >> i'm not going to put my life on hold for a year. not sick, going to make myself sick and probably not get rid of it anyway. >> the disease grew worse. >> you think, oh my god, what if you don't see it graduate from high school. what if i don't see her get married. >> an experimental drug might help. became the first to enroll in a clinical trial. he took the drug to interferon and riboviron, she showed no sign of the virus. c-vac was approved by the fda. the drugs have doubled the cure rate and some cases have doubled the treatment time. with an