5. X-ray, CT scan or MRI for lower back pain

Unfortunately, back pain is incredibly common — 80 percent of people will suffer from back pain some time in their lives. It can be both excruciating and debilitating. Naturally, people want to know what's wrong. Here's the catch: The best imaging machines in the world often can't tell them. Many older people with no back pain can have terrible-looking scans.

Most back pain goes away in about a month and imaging tests tend to lead to expensive procedures that often don't help recovery. One study found that people who got an MRI during the first month of their back pain were eight times more likely to have surgery than those who didn't have an MRI — but they didn't get relief any faster. If you don't feel better in a month, talk to your doctor about other options such as physical therapy, yoga or massage. But if your legs feel weak or numb, you have a history of cancer or you have had a recent infection, see your doctor as soon as possible.

6. Yearly Pap tests

The yearly Pap smear is a common part of women's health checklists, but it doesn't need to be. Women at average risk only need them every three years, since cervical cancer generally takes 10 to 20 years to develop. If women have also had negative tests for the human papillomavirus (HPV), which is now known to cause the cancer, they only need a Pap test along with the HPV test every five years. And women older than 65 who have had several normal Pap tests in a row can stop having them altogether. Do note, however, that a yearly visit to an ob-gyn stays on the to-do list.

7. Bone density scan for women before age 65 and men before age 70

For the estimated 10 million people — mainly women —in the United States who have osteoporosis, bone-strengthening medications can lower the chances of breaking a bone. But many experts argue that for those ages 50 to 65 who have osteopenia — mild bone loss — testing and subsequent drug prescriptions may be a waste of time and money. Not only is the risk of fracture often quite low, medications such as Fosamax (alendronate) and Boniva (ibandronate) have been linked to throat or chest pain, difficulty swallowing, heartburn, muscle pain, bone loss in the jaw and thigh-bone fractures. And there's scant evidence that people with osteopenia get much benefit from the drugs.

To help keep your bones strong, try walking and weight-bearing exercises, says Blackwelder. Get enough calcium and vitamin D in your diet. If you smoke, quit.