A while back I had my eyes opened by this review by Alex John London of Adriana Petryna's wonderful book, When Experiments Travel: Clinical Trials and the Global Search for Human Subjects. One of Petryna's important points is that when drug-trials are conducted in the developing world, the populations on whom drugs are tested are not very similar to the populations to whom the drug companies expect, eventually, to sell most of their drugs. Not only that, but the drug companies know this, and can work to choose populations with particular characteristics favorable to good trial results. Of course, they can do that at home, too, using inclusion and exclusion criteria for drug trials. A letter in last week's JAMA drives the point home: hardly any drug studies in high-impact journals include patients with multiple chronic conditions--this, in spite of the fact that 28% of Americans, and 2 of 3 three seniors, have multiple chronic conditions; and treatment of multiple chronic conditions accounts for 66% of overall US healthcare expenditure, and 95% of Medicare expenditure. The letter's sobering conclusion: "Given the possible drug-to-drug, drug-to-disease, and disease-to-disease interactions that remain unexamined, most of the evidence gathered to date by [clinical trials] is of limited value to guide decisions about medication use by patients with multiple chronic diseases."