Photo: Greg Kessler

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Ever fill out those symptom checklists at the doctor's office? I can't remember the last time those lists were updated, but they should be: Scientists are making remarkable advances in connecting the dots about what may put you at risk for a variety of diseases. And we're now learning that some seemingly temporary health issues, from insomnia to low vitamin D levels, may contribute to serious problems down the road. Protect yourself by paying attention to these warning signs.