With a tight 52-48 majority in the Senate, Republicans need every vote they can get on important issues such as tax reform and rolling back Obamacare.

But, The Wall Street Journal noted, that is not easy with several members who are older and have health issues keeping them from the Senate floor.

Arizona Sen. John McCain, R-Ariz., 81, had to fly back to Washington in July after brain surgery that resulted in a cancer diagnosis, while his vote was needed to get to 50 that would allow debate on repealing and replacing key parts of the Affordable Care Act. (Vice President Mike Pence was able to break the tie.)

But McCain then voted against the actual bill, and voted against another attempt again this month, drawing the ire of many in his party.

In March, Sen. Johnny Isakson, R-Ga., 72, had to return in a wheelchair after back surgery to pass legislation to overturn an Obama regulation that stopped states from blocking funding to abortion providers.

It is not only healthcare legislation that hangs in balance of older GOP Senators' wellness. Sen. Thad Cochran, R-Miss., at 79, announced Monday he will not be returning to D.C. from prostate surgery as planned.

That puts into doubt whether the Senate will be able to hold a crucial vote this week on its budget. The Senate cannot vote on its tax overhaul plan without a budget, since Majority Leader Mitch McConnell, R-Ky., plans to use the budget reconciliation process to pass the tax plan.

Without budget reconciliation, Republicans need 60 votes, and they see no hope of swaying a single Democrat.

McConnell said Monday he hopes to see tax reform by the end of this calendar year.

According to the Journal, the average age in Congress is the highest in recent history. The average age of senators is 61.8. In 1981, the average age of Republicans in the Senate was 51.9, with Democrats at 54.7.