Identifying Predisposing Factors for Hyperopic Shift in Long-Duration Spaceflight.

INTRODUCTION

NASA identifies spaceflight-associated neuro-ocular syndrome (SANS) as a significant health concern for astronauts on missions exceeding 30 d. This retrospective analysis evaluates age, mission duration, and preflight bodyweight as risk factors for hyperopic shift, a component of SANS. Results may guide the development of prevention strategies for future missions and provide insight into similar conditions on Earth.

METHODS

Deidentified data were obtained from NASA' s Medical Evaluation Documents, Volume B database for astronauts who participated in space missions >30 d. Refractive outcomes were assessed using manifest refraction (MR) and manifest refraction spherical equivalent (MRSE), calculating the mean change between pre- and postflight measurements across both eyes. The cohort included 85 subjects for age and mission duration analyses and 84 for bodyweight. Each risk factor was divided into quintiles. Spearman's rank correlation identified associations between quintiles and hyperopic shift.

RESULTS

Age showed a significant positive correlation with hyperopic shift (MR: r = 0.373; MRSE: r = 0.353). Mission duration correlated with MR (r = 0.253) and showed a nonsignificant trend with MRSE (r = 0.195). Preflight bodyweight correlated significantly with MRSE (r = 0.242) and showed a similar nonsignificant trend with MR (r = 0.207).

DISCUSSION: Age was the strongest predictor of hyperopic shift. Mission duration and bodyweight showed weaker positive associations. Future investigations should define SANS with threshold criteria and use logistic regression. The relationship between these risk factors and other manifestations of SANS also warrants further investigation. Aldeghi TM, Higbee RG. Identifying predisposing factors for hyperopic shift in long-duration spaceflight. Aerosp Med Hum Perform. 2026; 97(8):627-632.