Disease prevalence and survey design effects: A response to Weir and Smith

Evidence provided by Weir and Smith, particularly the findings from the National Health and Nutrition Examination Survey (NHANES), leads us to conclude that an increase in arthritis prevalence during the 1990s in the United States is probable, but the trend is likely overstated in the Health and Retirement Study (HRS). We show that a mistake in our earlier method does not change substantively our previous conclusion that survey duration effects are occurring in the HRS, a finding that is also supported by a variety of regression models (including that of Weir and Smith). Furthermore, very little evidence exists for an upward trend among self-reporters in the National Health Interview Survey (NHIS), and less than 25% of the increase in the HRS over the 1990s can be attributed to increases in obesity. r 2007 Elsevier Ltd. All rights reserved.