Chronic kidney disease (CKD) affects nearly 37 million people (11%) in the US and is a leading cause of death and morbidity. Due to their older age and higher prevalence of comorbid conditions, the prevalence of CKD among veterans is approximately 34% higher than in the general population and the fourth most common chronic disease diagnosed among US veterans.1,2 US veterans and those with prior military service (MS) may be at a particularly high risk for CKD and associated health care outcomes including increased hospitalization and death. The observed excess burden of CKD is not mirrored in the general population, and it is unclear whether prior MS confers a unique risk profile for CKD.
Current estimates of CKD burden among veterans or those with prior MS are widely variable and have been limited by unique regions, specific exposure profiles, or to single health care systems. As such, there remains a paucity of data examining CKD burden more broadly. We performed a study in the adult population of the US to quantify associations with the extent of CKD, enumerate temporal trends of CKD among those with prior MS, describe risk within subgroups, and compare heterogeneity of risk factors for CKD by MS.
Methods
The National Health and Nutrition Examination Survey (NHANES) is a suite of nationally representative, cross-sectional surveys of the noninstitutionalized US population. It is conducted by the National Center for Health Statistics and uses a stratified, clustered probability design, with surveys carried out without interruption, collated, and made accessible to the public at 2-year intervals.3 The survey consists of a questionnaire, physical examination, and laboratory data.
The inclusion criteria for our study were age ≥ 20 years along with serum creatinine and urinary albumin-creatinine measurements. The following definitions were used for the study:
• CKD: Estimated glomerular filtration rate < 60 mL/min/1.73 m2 calibrated to isotope dilution mass spectrometry (IDMS).
• Traceable: Creatinine-based CKD Epidemiology Collaboration formula or urinary albumin-creatine ratio ≥ 30 mg/g.
• MS: Positive response to the questions “Did you ever serve in the Armed Forces of the United States?” (1999 to 2010) or “Have you ever served on active duty in the US Armed Forces, military Reserves, or National Guard?” (2011 to 2018).
• Diabetes: Self-reported history, medication for diabetes, or glycated hemoglobin ≥ 7%.
• Hypertension: Blood pressure ≥ 140/90 or ≥ 130/40 mm Hg in the presence of diabetes, medication for hypertension, cardiovascular disease, or CKD, myocardial infarction, cardiac failure, or cerebrovascular disease by self-report.2,3
Analysis
Primary sampling unit, stratum, and weight variables were employed throughout to generate parameter estimates that are generalizable to the US population.4,5 The χ2 test and logistic regression, respectively, were employed for comparison of proportions and estimation of odds ratios. R Version 4.1.2 was employed for data analysis.