Chronic Kidney Disease and Military Service in US Adults, 1999-2018
Background: Although the management of chronic kidney disease (CKD) has changed considerably in US adults, it is uncertain whether the burden, risk factors, and temporal trends of CKD are similar regarding prior military service.
Methods: This observational study used National Health and Nutrition Examination Survey data to quantify the association between CKD and military service in a generalizable sample of US adults between 1999 and 2018.
Results: The respective frequencies (standard error [SE]) of CKD and military service were 15.2% (0.3) and 11.5% (0.3). The proportion (SE) with CKD was significantly higher among those with prior MS vs the overall population (22.7% [0.7] vs 15.2% [0.3]; P < .001). Within the military service population, the proportion (SE) with CKD differed by era: 1999 to 2002, 18.9% (1.1); 2003 to 2006, 24.9% (1.5); 2007 to 2010, 22.3% (1.5); 2011 to 2014, 24.3% (1.7); and 2015 to 2018, 24.0% (1.8) (P = .02). Following adjustment for age, sex, and race and ethnicity, prior military service was associated (P < .05) with a higher likelihood of CKD (adjusted odds ratio, 1.17; 95% CI 1.06-1.28). Adjusted associations of CKD differed in groups with and without military service for the 40 to 64 years age group, ≥ 65 years age group, female sex, and family poverty (P < .05 vs variable-specific reference category).
Conclusions: Military service is associated with a higher likelihood of CKD in US adults. Risk factors for CKD differed among many subgroups both with and without military service history. Future research is needed to better determine whether military service constitutes a unique risk factor for CKD.
Limitations
Our study has several limitations, including its cross-sectional study design, a lack of longitudinal data within individuals, and exclusion of institutionalized individuals. Limitations notwithstanding this study has several important aspects. As prior MS is highly variable, we were limited in our inability to stratify by service type or length of service. For example, veteran status is conferred to a “Reservist or member of the National Guard called to federal active duty or disabled from a disease or injury incurred or aggravated in line of duty or while in training status also qualify as a veteran” (13 CFR § 125.11). For the purposes of our study, prior MS would include all active-duty service (veterans) as well as reservists and National Guard members who have not been activated. This may be more representative of the overall effect of MS, as limitation to those receiving care within the VA may select for an older, more multimorbid population of patients, limiting generalizability.
In addition, more detailed information regarding service-related exposures and other service-connected conditions would allow for a more granular risk assessment by service type, era, and military conflict. Our finding of excess CKD burden among those with prior MS compared with the overall population is timely given the recent passage of the Promise to Address Comprehensive Toxics (PACT) Act. Exposure to and injury from Agent Orange—a known service-connected exposure associated with incident hypertension and diabetes—may be a significant contributor to CKD that may have a significant era effect. In addition, water contamination among those stationed in Camp Lejeune in North Carolina has notable genitourinary associations. Finally, burn pit exposures in more recent military conflicts may also have important associations with chronic disease, possibly including CKD. While similar attempts at the creation of large-scale US veteran cohorts have been limited by incomplete capture of creatinine, the large proportion of missing race data, and limited inclusion of additional markers of kidney disease, our use of a well-described, nationally representative survey along with standardized capture of clinical and laboratory elements mitigate the use of various societal or other codified definitions.1
Conclusions
Prior MS is associated with an increased risk of CKD overall and across several important subgroups. This finding was observed in various unadjusted and adjusted models and may constitute a unique risk profile of risk.
