What does skin cancer have to do with Parkinson's disease, the degenerative brain condition that causes tremors, slowed gait and problems with balance and coordination? According to a new study, more than you might think.

People with a family history of melanoma, the deadliest form of skin cancer, have twice the risk of developing Parkinson's disease as people who didn’t have a parent or sibling with the cancer, according to research released today ahead of April's annual American Academy of Neurology meeting in Seattle. The study followed nearly 132,000 men and women for 14 to 20 years; at the end of that period, 543 people had developed Parkinson's. The likelihood of getting Parkinson's was almost double — 90 percent greater, to be exact — in those with a close relative who had received a melanoma diagnosis than among those without that family history. (For comparison, the baseline risk of Parkinson’s is about 1 percent for those over 60, according to the Michael J. Fox Foundation.)

Do you obsessively scrutinize your skin for unusual blemishes and visit your doc for an annual whole-body check for cancer? It may not do you any good, a panel of government experts says.

The U.S. Preventive Services Task Force (USPSTF) says there isn’t enough evidence for or against the checks, during which you or your doctor looks for changes in the color, size and texture of skin growths. The panel's position—which reinforces guidelines it published in 2001—appears tomorrow in the Annals of Internal Medicine. The guidelines apply to people without noticeable changes in the symmetry, border, color or diameter of their moles—not to people with those symptoms or with a cancer history, says Tracy Wolff, a medical officer with the USPSTF who co-authored the paper.

Voters know a little bit more about Republican vice presidential nominee Sarah Palin’s health as they head to the polls today. According to a two-page letter released by her physician last night, Palin, 44, is in "excellent health and has no known health problems that would interfere with her ability to carry out the duties and obligations of vice president of the United States." 

Until now, Americans knew next to nothing about Palin’s health, other than that she gave birth to five children, the youngest of whom was born with Down Syndrome in April. (People with Down Syndrome have an extra copy of chromosome 21, and have mental and sometimes physical deficits, including heart abnormalities.) According to Palin's doctor, Cathy Baldwin-Johnson, the births were the only time the veep wannabe has been hospitalized.

Republican presidential candidate Sen. John McCain has a 6 percent chance of dying of the skin cancer melanoma in each of the next two years, says a doctor who specializes in the design of medical trials.

McCain, 72, has battled melanoma four times, most recently in 2002. After his campaign released 1,200 pages of his medical records in May, his doctor said he had less than a 10 percent chance of the melanoma recurring.

Now, in a letter to the medical journal The Lancet, internist John Alam explains his analysis of those records, based on a predictive model for 10-year survival in melanoma patients. Alam is a biotech consultant in Massachusetts who's contributed money to the Democratic Party and its presidential nominee, Barack Obama.

How much do voters need to know about a presidential candidate's health, and what information should politicians be obligated to share?

The New York Times takes an in-depth look at those questions today, concluding that candidates are sharing less medical information now than in some recent elections, despite candidates' previous health concerns. According to the article, the presidential and vice presidential candidates have only released limited and, in the case of GOP veep pick Sarah Palin, no medical records to date.

We know from a May review of some of John McCain's medical records and from previous reports that the Arizona senator has battled the most deadly form of skin cancer melanoma. His physician says McCain, who at 72 would be the oldest man ever sworn into a first term as president, has not  displayed any memory problems, but she has not said whether her patient has undergone cognitive tests.