In a society that seems to embrace retirement years, a University of Michigan study yields some surprises. It found more than two-thirds of those who worked after age fifty said working boosts their physical and mental health. Those still working past sixty-five were more likely to say work has very positive effects on their health, including helping keep their brains sharp. However, researchers found a variety of barriers to working past retirement age, such as chronic illness. Age discrimination in the work-place was listed as another barrier. Thirty-eight million older adults are in the workforce now, more than two and one-half times the number from forty years ago. Information came from more than three thousand adults between fifty and ninety-four.