DEAR DR. ROACH: I am a 69-year-old woman who was diagnosed three months ago with a 90-percent-blocked left renal artery, which was stented. Because my blood pressure was difficult to control following surgery, I was prescribed amlodipine and metoprolol. Approximately 10 years ago, I was diagnosed with a 65 percent to 70 percent blocked right carotid artery. The vascular surgeon who stented my renal artery advised that I also had a 60 percent to 70 percent blocked SMA, but said that he did not want to address this situation until I began having symptoms (abdominal pain after eating). I am a former smoker, exercise regularly, eat a balanced diet and am slim. I was diagnosed with elevated blood pressure and cholesterol, and I dutifully saw my physician twice per year and took medications as prescribed. I am very confused -- did my medications fail? Was I not prescribed a large enough dosage? My primary care physician and vascular surgeon don’t answer these questions, although my vascular surgeon did state that even though I quit smoking many years ago, “the damage was done.” It seems to me that if I have these artery issues, I may be headed for stroke, which scares me. Your advice will be greatly appreciated. -- A.

ANSWER: Atherosclerosis, the disease that causes blockages in arteries, is the leading cause of death in this country. Although we have good treatments, the treatments we have aren’t perfect. They can slow down the progression, and in some cases even start to reverse it, but we don’t have a cure. You have had at least three partially blocked arteries: the internal carotid in your neck, the renal artery to your kidney and the superior mesenteric artery (SMA) going to the pancreas and intestines.

I understand why you are concerned about stroke. A stroke is caused by death of brain cells, usually from not enough oxygen getting to them from a blocked blood vessel. Control of blood pressure and cholesterol reduce risk of stroke. Aspirin or other medications like it reduce risk of stroke in high-risk people.

It sounds like you and your doctor have done everything right -- you quit smoking and took your medications. These definitely reduced risk of further blocked arteries, including those in your heart and brain.

DEAR DR. ROACH: I wonder how we should view the expiration date on sunscreen. I would appreciate your medical view on this. Are they just put there to make us purchase more? -- H.L.C.

ANSWER: All products lose effectiveness over time. Sunscreen generally lasts for three years. It will gradually lose effectiveness after that.

You are better off getting a fresh bottle soon after expiration, but more importantly, you should be using enough per application -- and reapplying frequently -- so that a bottle should get used up in sooner than three years. While sunscreens help protect against sunburn, the jury is still out on how well they protect against cancer. Staying out of the sun during the middle part of the day and wearing sun-protective clothing are more effective than sunscreens.

DEAR DR. ROACH: Can a medical doctor refuse service to a new patient if he or she has Medicare? If so, will this change under Obamacare? -- J.R.

ANSWER: Doctors are under no obligation, as individual practitioners, to accept Medicare. Almost all hospitals, on the other hand, are obliged to take Medicare. The Affordable Care Act does not address this, to the best of my knowledge.