Effect of sex on aging-related decline of dopamine transporter in healthy subjects.

Objective: Aging decreases dopamine transporter (DAT) availability of striatum both in humans and rodents. We aimed to investigate the relationship of DAT availabilities from ventral striatum, caudate nucleus, and putamen with aging in healthy subjects.

Methods: I-FP-CIT single photon emission computed tomography (SPECT) was performed in all subjects. Specific binding of I-FP-CIT regarding DAT was calculated using a volume-of-interest-based analysis of ventral striatum, caudate nucleus, putamen. The cerebellum was chosen as a reference region. Specific binding ratios (SBRs) were calculated as follows: SBR = (target- cerebellum)/cerebellum.

Results: A total of 166 healthy subjects (109 males and 57 females) were included in this study. SBRs of ventral striatum, caudate nucleus, and putamen were negatively correlated with age. In young males, SBRs of ventral striatum and putamen were not correlated with aging. However, SBRs of caudate nucleus showed the trend toward negative correlation with age in the young group. In old males, SBR of caudate nucleus was negatively correlated with age and SBR of ventral striatum showed a trend toward negative correlation with age. Slopes of regression lines were not significantly different according to age groups in ventral striatum, caudate nucleus, or putamen. SBRs of ventral striatum, caudate nucleus, and putamen were negatively correlated with age in young females, but not in old females. Interestingly, slopes of regression line were significantly different between young and old females in ventral striatum, caudate nucleus, and putamen.

Conclusions: We have shown that slopes of regression lines of DAT availabilities and age were significantly different between young and old subjects in females, not in males. Therefore, sex has an impact on aging-related decline of striatal DAT availability.