One of the economic mysteries of the last few years has been the bigger-than-expected slowdown in health spending, a trend that promises to bolster wages and help close the wide federal deficit over the long term — but only if it persists. Major new studies from researchers at Harvard University, the Henry J. Kaiser Family Foundation and elsewhere have concurred that at least some of the slowdown is unrelated to the recession, and might persist as the economy recovers. Michael E. Chernew, HMS professor of health care policy, is one of the lead authors.