Dopamine Transporters Decrease with Age

Postmortem studies have documented degeneration of dopamine cells with age, but the changes that occur in healthy aging individuals is less clear. The purpose of this study was to evaluate the extent to which age-induced changes in dopamine transporters occur in subjects with no evidence of motor impairment. Methods: We evaluated 23 right-handed healthy volunteers (age range 20-74 yr) using PET and [¹¹C]d-fhreo-methylphenidate. The ratio of the distribution volume for [¹¹C]d-threo-methylphenidate in striatum to that in cerebellum was used as model parameter for dopamine transporter availability (Bmax/Kd + 1). Results: Dopamine transporter availability was significantly lower in subjects >40 yr of age than in those <40 yr. Estimates of dopamine transporter availability showed a significant negative correlation with age both for the putamen (r = -0.72, p < 0.0001) and the caudate (r = -0.74, p < 0.0001). Dopamine transporter availability was higher in the left than in the right putamen but did not differ between the left and right caudate. Conclusion: This study documents a 6.6% decrease per decade of life in striatal dopamine transporters of healthy volunteers.