Question: I've been taking Nexium for several years now to treat Barrett's esophagus. I have heard long term use of acid blocking drugs such as Nexium can increase the risk of pneumonia. Why would it cause that? How much of a risk is it for me? - R.P., Huntsville, Ala.

Answer: The timing of your question is superb, because a recent retrospective study conducted by researchers at the Massachusetts General Hospital Department of Medicine poked huge holes in the conclusion of previous studies linking chronic use of proton pump inhibitors (PPIs) such as Nexium and Prilosec to a roughly 1 percent per year increased risk of developing pneumonia. The widely held belief has been that suppressing stomach acid can allow the growth of ingested bacteria to increase the risk of pneumonia. The belief is so strong the FDA has issued warnings over it.

To disprove this association, Dr. Anupam Jena and his colleagues at Massachusetts General Hospital used the strategy of "falsification." They analyzed 11 years of insurance claims from 54,500 adults, both PPI users and non-PPI users, as to whether they had received diagnosis or treatment for health problems such as osteoarthritis, chest pain, urinary tract infections and skin infections - conditions which would be expected to have no increased risk from PPI use.

The results showed folks taking PPIs such as Nexium were more likely than non-PPI users to have osteoarthritis, chest pain and urinary tract infections, along with pneumonia. They were also more likely to be diagnosed or treated for conditions including cancer, diabetes or stroke - conditions that have nothing to do with use of PPI drugs such as Nexium.

Based upon their research analysis published online in the Journal of General Internal Medicine, it appears Nexium will not increase your risk of pneumonia.

Question: Since our DNA can be detected from our blood, do we also pick up a blood donor's DNA when we receive a blood transfusion? - M.H., Roswell, Ga.

Answer: The short answer is no. When we receive blood, we are not usually receiving a blood donor's whole blood; rather, only the red blood cells. The DNA resides in a cell's nucleus, and since mature red blood cells don't have a nucleus they don't have any DNA material. Whole blood contains not only red blood cells, but other components lsuch as serum, white blood cells, platelets and antibodies. It is the white blood cell component of whole blood that contains the nuclei and therein one's genetic material in the form of DNA.

However, even if one received a whole blood transfusion rather than the red blood cells alone, the DNA profile of a donor will not be detected in the peripheral blood of a recipient. In one study, a woman in a trauma situation was transfused with 14 units of blood (four of those units being whole blood) without showing any detectable level of foreign DNA. In another study, a man in a trauma situation received 13 units of blood (four of those units being whole blood) without showing any detectable level of the donor's DNA. That's a lot of blood they received, considering the average woman has 8 to 10 pints/units of whole blood and the average man has 10 to 12 pints/units of blood.

Dr. Mitchell Hecht is a physician specializing in internal medicine. Send questions to him at: "Ask Dr. H," P.O. Box 767787, Atlanta, GA 30076.