A U.S. health-care overhaul could be good news for such real-estate investment trusts as Cogdell Spencer Inc. (CSA) and Healthcare Realty Trust Inc. (HR), two health-care REITs that play heavily in the medical office building sector.

Analysts say the possibility of millions of newly insured patients is likely to be another boost for a sector that already has a very positive long-term outlook.

Still, how much of an impact government health-care changes will have remains unclear, since Congress is still trying to decided how much of the health-care system will be changed under legislation. In addition, the sector remains challenged by doctors' concerns about their future reimbursement rates and patients' reluctance to run up new medical bills in the midst of an ailing economy.

Earlier this year, real estate firm Marcus & Millichap estimated that if 50% of the 46 million uninsured Americans gained coverage under a new national health policy, the added demand would require nearly 45 million square feet of medical office building space beyond what is normally needed. To put that into perspective, there's currently about 700 million square feet of medical office space nationally, according to the firm's research unit.

What's more, Marcus & Millichap Managing Director Alan Pontius said changes in health-care technology and data-center needs will drive demand in the space. Namely, the American Recovery and Reinvestment Act of 2009 allocated about $19 billion to help compile electronic medical records for U.S. residents, which could create a new tenant group for medical office buildings.

Major players in the industry have been taking notice of the sector's potential.

All the health-care REITs "are trying to increase exposure to the segment," said David Aubuchon, analyst at Robert W. Baird & Co.

Medical office buildings often house doctor's offices, such diagnostics devices as X-ray machines, and chemotherapy treatment centers. Although the sector is fragmented with many small and regional players, publicly traded health-care REITs own a sizable stake in the billion dollar industry.

Medical buildings have generally fared better than traditional office properties during the economic downturn, partly because health-care services are more resilient during bad times. The aging U.S. population is another reason for optimism for the health sector, and existing medical buildings have also benefited from a slowdown in new construction.

Such health-care REITs as Cogdell Spencer and Healthcare Realty Trust, whose holdings are focused in medical buildings, seem poised for an uptick in patients for tenants.

"If people are less dependent on the emergency room for care, I think that's good for medical office and ambulatory care," said Frank Spencer, chief executive of Cogdell Spencer.

It and other health care REITs have made no secret of their keen eye for acquisitions.

In December, Ventas Inc. (VTR) acquired three medical office buildings for about $62.5 million. A month before, Nationwide Health Properties Inc. (NHP) reached an agreement in principle to buy several medical buildings from Pacific Medical Buildings LLC, restarting a deal that had been put on hold when the capital markets froze up.

More deals are likely in the coming year if credit continues to become more available, analysts say.

Yet hopes may be tempered should doctors get squeezed on reimbursement rates under a new health-care overhaul, said George Skoufis, credit analyst at Standard & Poor's, although he noted there remains much uncertainty about the outcome of government efforts to change the system.

And although watchers consider medical office buildings to be resilient during an economic downturn, they have not been recession-proof. With higher vacancies in 2009 compared with a year earlier, due in part to some patients putting off medical care while times are tough, rent growth has been limited in some areas of the country, analysts say.

Still, despite some of the sector's near-term challenges, the prognosis seems promising.

"It's a good long-term asset class," said Aubuchon.

-By Veronica Dagher, Dow Jones Newswires; 212-416-2261; veronica.dagher@dowjones.com