Uncertainty has returned. Although congressional Republicans have failed to overturn the Affordable Care Act after the 2016 election, the Trump government has tried to weaken it, and a Texas federal judge ruled in December that this law was unconstitutional. This decision has no effect as long as it is on appeal, but it does not help the industry because a final decision could take years and go to the Supreme Court. "This adds uncertainty," said Ms. Hynes.

These problems, as well as the sector's outperformance in recent years, may make health a less efficient player in these difficult times, but the record is certainly remarkable.

"You go to a doctor and buy drugs, good or bad economically," said Scott Wren, chief global equity strategist for the Wells Fargo Investment Institute.

The data shows that the sector performed well during the market struggles. According to Bank of America Merrill Lynch's research, in the last six down markets since 1973 – defined as a 20% or more drop from the top of the market – when the S & P 500 has lost 39% on average, Healthcare outperformed the S & P by 11 percent annualized.

It only underperformed consumer staples, energy and utilities. And, according to CFRA Research, since 1946, health care has outperformed the market as a whole 75% of the time during similar recessions.

In times of economic uncertainty, consumers tend to reduce what they do not need. While enthusiasm for restaurants or a new smartphone may weaken, the need for medical care persists.

The rise in health care stocks in recent years has made the industry more expensive than the overall market, with a price / earnings ratio of 20 for S & P healthcare stocks 500, compared with just 17.7 for the entire index, according to Bloomberg. .

"It's a good place to hide," says Lindsey Bell, investment strategist at CFRA Research. If a recession were to hit, it would not mean that health care would be safe; It's "not bulletproof," Ms. Bell said.