+Gz Exposure and Flight Duty Limitations.

High +G exposure is known to cause spinal problems in fighter pilots, but the amount of tolerable cumulative +G exposure or its intensity is not known. The aims of this study were to assess possible breaking points during a flight career and to evaluate possible determinants affecting pilots' spines. Survival analysis was performed on the population who started their jet training in 1995-2015. The endpoint was permanent flight duty restriction due to spinal disorder. Then the quantified G exposure and possible confounding factors were compared between those pilots with permanent flying restriction and their matched controls. Cumulative G exposure was measured sortie by sortie with fatigue index (FI) recordings. FI is determined by the number of times certain levels of G are exceeded during the sorties. The linear trend of the survival curve indicates an annual 0.86% drop out rate due to spinal problems among the fighter pilot population. A conditional logistic regression did not find any difference in the FI between cases and controls (OR 0.96, 95%CI 0.87-1.06). No statistical difference was found for flight hours, a sum of intensive flying periods, fitness tests, or with nicotine product use. Additionally, a maximum +G limitation without airframe restriction was assessed and is presented as a useful tool to manage loading and developed symptoms. No particular breaking point during follow-up or individual factor was found for G induced spinal disorders. The results of the study outline the multifactorial nature of the problem. Thus, multifactorial countermeasures are also needed to protect pilots' health.