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People who have a variant gene and are exposed to certain pesticides may have a higher risk of Parkinson’s disease, a new study finds. Researchers tested a variety of pesticides. They found that several of them interfere with the function of an enzyme called ALDH. This enzyme helps to break down chemicals that kill brain cells involved in making dopamine. People with Parkinson’s disease have too little dopamine. Researchers asked about exposure to pesticides among people who were part of a study of Parkinson’s risk in 3 California farming counties. In all, 360 people had Parkinson’s and 816 people did not. Some people had a different (variant) version of a gene that provides instructions for making ALDH. Researchers looked at Parkinson’s rates in people exposed to the pesticides that interfere with ALDH.

Cancer doctors should ask about patients’ family medical history. But two generations are enough, new guidelines say. The American Society of Clinical Oncology released the guidelines. They say that doctors should ask about cancer among patients’ first- and second-degree relatives. But going back three generations — the old advice — is not necessary. A panel of experts based the changes on a review of evidence. They decided that information about more distant relatives is less likely to be correct. First-degree relatives include parents, children, brothers and sisters. Second-degree relatives include grandparents, aunts and uncles. Nieces, nephews, grandchildren and half-siblings also are considered second-degree. Doctors should ask the relative’s type of cancer, age when diagnosed and race or ethnic group, the guidelines say.