The economic slowdown has swelled the ranks of people without health insurance, and now it is also threatening people who have insurance but find that the coverage is too limited or that they cannot afford their own share of medical costs. Higher premiums, less extensive coverage, and bigger out-of-pocket deductibles and co-payments are causing many of the 158 million people covered by employer health insurance to struggle to pay for medical expenses. Many doctors say the soft economy is even making some insured people hesitant to get care they need.