Factors Associated With Testicular Cancer Risk Among New American Military Recruits During Wartime

Infantry soldiers had twice the adjusted testicular cancer risk of other Army occupations — but combat deployment showed no association

Journal: American Journal of Men's Health | Published: 2026-03-15 | Type: Journal Article | PMID: 41833285 Authors: Nelson DA, Hill OT, Skaggs SA, Brown WJ (University of Texas Health Science Center at San Antonio) Funding/COI: Not listed; authors declared no conflicts of interest

Summary

Among 210,483 new U.S. Army recruits followed from 2011–2014, infantry soldiers were diagnosed with testicular cancer at roughly twice the rate of men in other military occupations. Counterintuitively, combat deployment itself showed no statistically significant association with testicular cancer risk. The authors are careful to flag that this infantry signal could be confounding — men who choose infantry may share unmeasured traits that independently raise risk — and they cannot establish causation.

Claims

• 44 incident testicular cancer diagnoses in 210,483 men over 378,770 person-years (period prevalence: 0.02%; incidence rate: 11.61 per 100,000 person-years)
• Infantry soldiers: 2x adjusted hazard for testicular cancer vs. all other occupations (p = .045)
• Infantry accounted for 38.64% of all cases (17 of 44) despite being one occupation among many
• Peak incidence in infantry was 31.94 per 100,000 person-years in the 6–13 month service window
• Combat deployment: no statistically significant association with testicular cancer in adjusted or unadjusted models
• White race: 95.45% of cases (p < .001); adjusted risk increased with age and decreased with longer service time

Study Quality

This is a retrospective cohort using official U.S. Army administrative and health records — a methodological strength that avoids recall bias and self-report error. The longitudinal panel design with time-series data ordering (predictors precede outcomes) reduces reverse causation risk. A multivariable survival regression adjusting for age, race, and service time is appropriate for this data structure.

The critical weakness is the event count: 44 cases in a 210,000-person cohort is a sparse outcome for a multivariable model. With so few events, the twofold infantry hazard ratio is statistically fragile — small changes in a handful of cases could shift the estimate substantially. The ICD-9 coding endpoint is reasonable but relies on care sought within the military health system; diagnoses obtained under a civilian spouse's insurance or out-of-pocket would be missed, introducing outcome misclassification of unknown magnitude.

Red Flags

• 44 events: The entire inference rests on 44 cases. Any multivariable model with this few outcomes should be treated as hypothesis-generating, not confirmatory.
• Selection confounding for infantry: Men who enlist as infantry differ from other soldiers in ways the authors could not measure — physical screening, age profile at entry, socioeconomic background. The paper explicitly acknowledges this cannot be ruled out.
• Maximum 48-month follow-up: Testicular cancer latency from occupational exposure can extend beyond 4 years. The absence of a combat association may simply reflect insufficient observation time, not absence of effect — the authors acknowledge this directly.
• Single service branch: U.S. Army only; findings may not generalize to Marines, Navy, Air Force, or other militaries.
• Outcome capture: Diagnoses made outside the Military Health System (e.g., civilian insurance) are invisible to the study.
• No exposure data: "Infantry occupation" is a proxy, not an enumerated list of specific occupational exposures. The paper cannot identify which features of infantry service might be responsible.

Strengths

• Very large base population (210,483) providing robust denominator data
• Official administrative records reduce information bias
• Longitudinal design with time-ordered covariates
• Transparent about the confounding they cannot control
• Observed incidence rate (11.61/100,000 person-years) aligns with CDC benchmarks for comparable age ranges, supporting data validity
• Addresses a genuine gap: occupational testicular cancer research in young military men is sparse

Verdict

This paper surfaces a suggestive signal — infantry soldiers developing testicular cancer at twice the rate of other occupations — but 44 cases is too thin a foundation to conclude much. The authors know this and say so clearly, which is the appropriate posture. The finding is worth a targeted follow-up study with longer follow-up, specific exposure characterization, and ideally a multi-branch dataset. The combat deployment null result is interesting but also undermined by a follow-up window that may simply be too short for latent carcinogenic effects. Treat this as a well-executed, well-caveated hypothesis generator — not a definitive occupational risk finding.