Most retirees or would-be retirees have heard the stories–about doctors who no longer accept Medicare patients, or who have opted out of the program entirely. But a new study indicates that fears about not having access to health care in later life are largely overstated. About 47 million Americans are already enrolled in Medicare, and the bulk of the baby-boom generation has yet to reach 65, the age at which a person normally qualifies for federal health insurance. The growing demands on the program – and repeated threats by Congress to cut Medicare payments to doctors – have sparked media reports in recent years about fed-up physicians washing their hands of all things Medicare.