Currently, little is known about differences in health care use and spending across states (or other geographic areas) for populations with multiple chronic conditions.

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People with mental health problems, or conditions such as asthma, Parkinson's disease, cancer, multiple sclerosis or cystic fibrosis must pay for many of their prescribed medicines and dressings.

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Eventually, fewer and cheaper sensors should do the trick, but Google and other researchers are still working out how to combine readings from multiple sensors, and determining which sensors work best in conditions such as night driving or heavy rain.

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