Abstract
Purpose::
To investigate differences between Whites and Blacks in the relationship between macular pigment optical density (MPOD), serum C-reactive protein (CRP), and serum levels of lutein and zeaxanthin (L&Z), in an elderly biracial sample of healthy subjects from the Mid-Southern US.
Methods::
We studied 180 subjects [mean age: 78.9 yo, 19% Blacks, 51% females, 34% lutein supplement users (LSUs)] participating in an ancillary study to the Health ABC Study, ARMA. MPOD estimates were obtained in all subjects with a heterochromatic flicker photometry-based method at 0.5 degrees of eccentricity from the fovea. Fasting serum samples were collected at time of visit and analyzed according to standardized protocols. L&Z and CRP were not normally distributed and were ln-transformed.
Results::
MPOD of Blacks (0.20 +/- 0.22, n=34) was significantly lower than in Whites (0.37 +/- 0.19, n=146; p= 0.00001). Despite the greater proportion of LSUs among Whites (37 vs. 21%), serum levels of both L&Z tended to be higher in Blacks (ln-L = 2.96 +/- 0.54 vs. 2.78 +/- 0.58 µg/dl; ln-Z = 1.48 +/- 0.49 vs. 1.31 +/- 0.43 µg/dl). This finding was not accounted for by serum ln-CRP levels, which too tended to be higher in Blacks (1.06 +/- 1.22 vs. 0.57 +/- 1.23 µg/ml). MPOD was positively correlated to serum levels of both L&Z in both Whites (r = 0.18 for L and 0.12 for Z) and Blacks (r = 0.17 for both L&Z). However, CRP was inversely correlated with MPOD (r = -0.19) and serum lutein levels (r = -0.15) only in Whites.
Conclusions::
In the elderly population, there are differences between Whites and Blacks in both MPOD and its serological correlates. The lower MPOD in Blacks despite (a) higher serum L&Z levels and (b) lack of correlation between MPOD and serum CRP levels in Blacks argues against the possibility that lower MPOD levels in Blacks may be explained simply by an overall greater inflammatory load. These findings suggest that, between Blacks and Whites, there are significant differences in the interaction between carotenoids and inflammation and in xanthophyll metabolism, both systemically and locally at the retinal level.
Keywords: aging • macular pigment • clinical (human) or epidemiologic studies: biostatistics/epidemiology methodology