ArticleBMC medical research methodology2026
Assessing nonresponse bias in a 30-year study of gulf war and gulf era veterans.
Article in BMC medical research methodology, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
What it found
Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.
The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
0 citing papers in PubMed.
No citing paper in PubMed yet.
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
9 authors.
Funding
No grant is acknowledged in the PubMed record.
Abstract
backgroundCohort studies of veterans are critical for understanding the long-term health effects of deployment and toxic exposures. However, longitudinal research is susceptible to attrition and potential nonresponse bias. The Gulf War Era Cohort Study (GWECS) is the largest and longest-running longitudinal cohort study of 1990–1991 Gulf War veterans. In this paper, we identify demographic and military service characteristics associated with patterns of response over time and examine the extent to which accounting for nonresponse bias in Wave 4, conducted more than 30 years after the Gulf War, might impact the estimates of health conditions.
methodMultivariate multinomial logistic regression analysis was used to identify demographic and military service characteristics associated with response patterns over time (always responder, current responder, past responder, never responder). To adjust for nonresponse at Wave 4, a search algorithm was used to identify predictors of response and form weighting class cells. The effectiveness of nonresponse adjustments was evaluated by (1) comparing estimates of demographic and military characteristics before and after weighting, (2) examining the correlation between the weighting classes and health outcomes, and (3) comparing early and late responders on health outcomes.
resultsWave 4 obtained a response rate of 47%, close to the 50% response rate obtained in Wave 3 over a decade earlier. Veterans most likely to respond to the survey over time and in Wave 4 were older, White, deployed, officers, and married in 1991. Weighting adjustments accounted for these differences and reduced bias in demographic and military characteristics, as well as in survey variables related to those characteristics. However, differences observed between early and late responders on alcohol and drug dependence suggest that these conditions may be underestimated.
conclusionGWECS achieved a relatively high response rate in the most recent follow-up. Although differential response occurred, nonresponse adjustments effectively reduced bias in the key variables examined. This cohort continues to provide insight into the long-term health effects of Gulf War deployment, including cancer and chronic conditions, as the cohort ages.
Indexed as
Identifiers
What OpenQuestion holds
Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.