Though eligible for Medicare, some dialysis patients prefer private insurance because it can be more flexible. The Affordable Care Act made that insurance easier to get. It requires insurers to cover such patients, says insurers can't charge those patients more, caps out-of-pocket expenses and helps less-wealthy patients cover premiums.

The Republican replacement for the ACA, the American Health Care Act, seems designed to be a pain for dialysis firms. The law may let states apply for waivers of the regulations that have made private insurance more attainable. If given the opportunity, insurers would likely make plans covering dialysis patients prohibitively expensive, to help keep such people out of their risk pool.

Dialysis companies have already been curtailed in their ability to nudge patients toward commercial insurance by funding third-party charities that help pay for it. The AHCA has the potential to enhance their woes by pricing patients out of the private insurance market, charity or no.

Not every part of the health care sector is quite as exposed to the AHCA as dialysis is. But most companies have similar risks, for which stock prices have failed to fully account.

Drugmakers, for example, also spend significant amounts of money funding charities that help cover out-of-pocket drug costs for patients on expensive medicines. Those costs are expected to rise substantially if the ACA is repealed, hitting revenue and increasing the political and public pressure over high drug prices.

A Kaiser Family Foundation analysis found that 75 percent of individual insurance plans in the pre-ACA era didn't cover maternity care, 45 percent didn't include substance-abuse services, 38 percent didn't include mental and behavioral health services, and 17 percent had prescription-drug restrictions. The ACA brought those percentages down significantly.

Under the AHCA, the individual insurance market is likely to head back to those bad old days in some states, pricing people out of comprehensive coverage -- and hurting companies that provide these services and products.

That will have widespread and unpredictable knock-on effects throughout health care. People who don't get mental health care also don't get prescribed medication, and so on.

This is not a small-scale or narrowly concentrated problem. Twenty-three million people are expected to lose health coverage outright under the AHCA, according to the Congressional Budget Office. An unknown number will have substantially skimpier coverage or higher out-of-pocket costs that may dissuade them from getting care. Millions of Americans with employer-sponsored coverage may once again face annual and lifetime coverage limits.

Yet health care stocks in the Russell 3000 index of the largest U.S. companies are outperforming the index as a whole since the election. A few stocks with ACA exposure are down since the election, but many more are up.

It's become increasingly clear health care investors can't rely on the Senate to save them. The Senate has gone from publicly decrying the House bill to reportedly working on something that copies it in many respects. There's not all that much room to soften the House bill, anyway, despite President Donald Trump apparently having come to believe the House bill is "mean." The revised bill is being designed in secrecy and hastened to a vote (again) for a reason.

The consequences aren't always as obvious as they are for dialysis firms. But they're there, and health care investors appear to be in some denial about it.

Peter Grauer, the chairman of Bloomberg LP, the parent company of Bloomberg News, is a member of DaVita’s board.

This column does not necessarily reflect the opinion of Bloomberg LP and its owners.

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