Few studies have examined a possible correlation between cervical disc degeneration and disc height. The aim of this study was to establish age-related changes and sex-specific differences of cervical disc height using magnetic resonance imaging (MRI) and to evaluate the relationship between degree of cervical disc degeneration and disc height in asymptomatic subjects. We measured the intervertebral disc anteroposterior diameter and disc height in each disc level using MRI in 1211 relatively healthy volunteers (606 men and 605 women, mean age 49.5 years). We included at least 100 males and 100 females in each decade of life between the 20s and the 70s. Cervical disc degeneration was defined according to the modified Pfirrmann classification system, and disc index and intervertebral disc height narrowing ratio were evaluated on sagittal plane MRI. Intervertebral disc height decreased gradually with increasing age in both sexes. The grade of disc degeneration significantly increased with age in both sexes at every level. Mild disc degeneration was observed even in subjects their 20s. Disc degeneration occurred around the C5-C6 level. The average disc height decreased with aging after the 40s. Disc index and intervertebral disc height narrowing ratio decreased with a progression in the disc degeneration grade in both sexes. This large-scale cross-sectional analysis of cervical spine MRI data in healthy subjects demonstrated that cervical disc height narrowing progresses with age. Cervical disc height narrowing is highly correlated with the progression of disc degeneration.