Julie A. Mares

Associations Between Age-Related Nuclear Cataract and Lutein and Zeaxanthin in the Diet and Serum in the Carotenoids in the Age-Related Eye Disease Study (CAREDS), an Ancillary Study of the Women's Health Initiative

OBJECTIVE To evaluate associations between nuclear cataract (determined from slitlamp photographs between May 2001 and January 2004) and lutein and zeaxanthin in the diet and serum in patients between 1994 and 1998 and macula between 2001 and 2004. DESIGN A total of 1802 women aged 50 to 79 years in Iowa, Wisconsin, and Oregon with intakes of lutein and zeaxanthin above the 78th (high) and below the 28th (low) percentiles in the Womens Health Initiative Observational Study (1994-1998) were recruited 4 to 7 years later (2001-2004) into the Carotenoids in Age-Related Eye Disease Study. RESULTS Women in the group with high dietary levels of lutein and zeaxanthin had a 23% lower prevalence of nuclear cataract (age-adjusted odds ratio, 0.77; 95% confidence interval, 0.62-0.96) compared with those with low levels. Multivariable adjustment slightly attenuated the association (odds ratio, 0.81; 95% confidence interval, 0.65-1.01). Women in the highest quintile category of diet or serum levels of lutein and zeaxanthin as compared with those in the lowest quintile category were 32% less likely to have nuclear cataract (multivariable-adjusted odds ratio, 0.68; 95% confidence interval, 0.48-0.97; P for trend = .04; and multivariable-adjusted odds ratio, 0.68; 95% confidence interval, 0.47-0.98; P for trend = .01, respectively). Cross-sectional associations with macular pigment density were inverse but not statistically significant. CONCLUSIONS Diets rich in lutein and zeaxanthin are moderately associated with decreased prevalence of nuclear cataract in older women. However, other protective aspects of such diets may in part explain these relationships.

Genetic evidence for role of carotenoids in age-related macular degeneration in the carotenoids in age-related eye disease study (CAREDS)

PURPOSE We tested variants in genes related to lutein and zeaxanthin status for association with age-related macular degeneration (AMD) in the Carotenoids in Age-Related Eye Disease Study (CAREDS). METHODS Of 2005 CAREDS participants, 1663 were graded for AMD from fundus photography and genotyped for 424 single nucleotide polymorphisms (SNPs) from 24 candidate genes for carotenoid status. Of 337 AMD cases 91% had early or intermediate AMD. The SNPs were tested individually for association with AMD using logistic regression. A carotenoid-related genetic risk model was built using backward selection and compared to existing AMD risk factors using the area under the receiver operating characteristic curve (AUC). RESULTS A total of 24 variants from five genes (BCMO1, BCO2, NPCL1L1, ABCG8, and FADS2) not previously related to AMD and four genes related to AMD in previous studies (SCARB1, ABCA1, APOE, and ALDH3A2) were associated independently with AMD, after adjusting for age and ancestry. Variants in all genes (not always the identical SNPs) were associated with lutein and zeaxanthin in serum and/or macula, in this or other samples, except for BCO2 and FADS2. A genetic risk score including nine variants significantly (P = 0.002) discriminated between AMD cases and controls beyond age, smoking, CFH Y402H, and ARMS2 A69S. The odds ratio (95% confidence interval) for AMD among women in the highest versus lowest quintile for the risk score was 3.1 (2.0-4.9). CONCLUSIONS Variants in genes related to lutein and zeaxanthin status were associated with AMD in CAREDS, adding to the body of evidence supporting a protective role of lutein and zeaxanthin in risk of AMD.

Genetic determinants of macular pigments in women the carotenoids in age-related eye disease study

PURPOSE To investigate genetic determinants of macular pigment optical density in women from the Carotenoids in Age-Related Eye Disease Study (CAREDS), an ancillary study of the Womens Health Initiative Observational Study. METHODS 1585 of 2005 CAREDS participants had macular pigment optical density (MPOD) measured noninvasively using customized heterochromatic flicker photometry and blood samples genotyped for 440 single nucleotide polymorphisms (SNPs) in 26 candidate genes related to absorption, transport, binding, and cleavage of carotenoids directly, or via lipid transport. SNPs were individually tested for associations with MPOD using least-squares linear regression. RESULTS Twenty-one SNPs from 11 genes were associated with MPOD (P ≤ 0.05) after adjusting for dietary intake of lutein and zeaxanthin. This includes variants in or near genes related to zeaxanthin binding in the macula (GSTP1), carotenoid cleavage (BCMO1), cholesterol transport or uptake (SCARB1, ABCA1, ABCG5, and LIPC), long-chain omega-3 fatty acid status (ELOVL2, FADS1, and FADS2), and various maculopathies (ALDH3A2 and RPE65). The strongest association was for rs11645428 near BCMO1 (βA = 0.029, P = 2.2 × 10(-4)). Conditional modeling within genes and further adjustment for other predictors of MPOD, including waist circumference, diabetes, and dietary intake of fiber, resulted in 13 SNPs from 10 genes maintaining independent association with MPOD. Variation in these single gene polymorphisms accounted for 5% of the variability in MPOD (P = 3.5 × 10(-11)). CONCLUSIONS Our results support that MPOD is a multi-factorial phenotype associated with variation in genes related to carotenoid transport, uptake, and metabolism, independent of known dietary and health influences on MPOD.

Vitamin D Intake and Season Modify the Effects of the GC and CYP2R1 Genes on 25-Hydroxyvitamin D Concentrations

Vitamin D deficiency {defined by the blood concentration of 25-hydroxyvitamin D [25(OH)D]} has been associated with many adverse health outcomes. Genetic and nongenetic factors account for variation in 25(OH)D, but the role of interactions between these factors is unknown. To assess this, we examined 1204 women of European descent from the Carotenoids in Age-Related Eye Disease Study, an ancillary study of the Womens Health Initiative Observational Study. Twenty-nine single nucleotide polymorphisms (SNPs) in 4 genes, GC, CYP2R1, DHCR7, and CYP24A1, from recent meta-analyses of 25(OH)D genome-wide association studies were genotyped. Associations between these SNPs and 25(OH)D were tested using generalized linear regression under an additive genetic model adjusted for age, blood draw month, and ancestry. Results were stratified by season of blood draw and, separately, vitamin D intake for the 6 SNPs showing a significant association with 25(OH)D at the P < 0.01 level. Two nonsynonymous SNPs in GC and 4 SNPs in CYP2R1 were strongly associated with 25(OH)D in individuals whose blood was drawn in summer (P ≤ 0.002) but not winter months and, independently, in individuals with vitamin D intakes ≥400 (P ≤ 0.004) but not <400 IU/d (10 μg/d). This effect modification, if confirmed, has important implications for the design of genetic studies for all health outcomes and for public health recommendations and clinical practice guidelines regarding the achievement of adequate vitamin D status.

Association Between Dietary Fat Intake and Age-Related Macular Degeneration in the Carotenoids in Age-Related Eye Disease Study (CAREDS) An Ancillary Study of the Women's Health Initiative

OBJECTIVE To evaluate the relationships between the amount and type of dietary fat and intermediate age-related macular degeneration (AMD). DESIGN Women aged 50 to 79 years with high and low lutein intake from 3 sites of the Womens Health Initiative Observational Study were recruited into the Carotenoids in Age-Related Eye Disease Study. Fat intake from 1994 through 1998 was estimated using food frequency questionnaires, and AMD was assessed photographically from 2001 through 2004. RESULTS Intakes of omega-6 and omega-3 polyunsaturated fatty acids, which were highly correlated (r = 0.8), were associated with approximately 2-fold higher prevalence of intermediate AMD in high vs low quintiles. However, monounsaturated fatty acid intake was associated with lower prevalence. Age interactions were often observed. In women younger than 75 years (n = 1325), total fat and saturated fatty acid intakes were associated with increased prevalence of AMD (multivariate adjusted odds ratios [95% confidence interval] for intermediate AMD, 1.7 [1.0-2.7] for quintile 5 vs quintile 1 for total fat [P = .10 for trend] and 1.6 [0.7-3.6] for saturated fatty acids [P = .23 for trend]). The associations were reversed in older women. CONCLUSIONS These results support a growing body of evidence suggesting that diets high in several types of fat may contribute to the risk of intermediate AMD and that diets high in monounsaturated fatty acids may be protective.

Healthy diets and the subsequent prevalence of nuclear cataract in women.

OBJECTIVE To assess the association between healthy diet scores and prevalence of nuclear cataract in women. METHODS The association between healthy diet scores, which reflect adherence to the US dietary guidelines, and prevalence of nuclear cataract determined 4 to 7 years later was assessed in a sample of Womens Health Initiative Observational Study participants (aged 50-79 years) residing in Iowa, Wisconsin, and Oregon. Scores on the 1995 Healthy Eating Index, which reflect adherence to 1990 guidelines, were assigned from responses to food frequency questionnaires at the Womens Health Initiative baseline (1994-1998). Presence of nuclear cataract was determined from slitlamp photographs and self-reports of cataract extractions were assessed from May 1, 2001, to January 31, 2004, in 1808 women participating in the Carotenoids in Age-Related Eye Disease Study. RESULTS Having a high 1995 Healthy Eating Index score was the strongest modifiable predictor of low prevalence of nuclear cataract among numerous risk factors investigated in this sample. The multivariate-adjusted odds ratio for high vs low quintile for diet score was 0.63 (95% confidence interval, 0.43-0.91). Higher prevalence of nuclear cataract was also associated with other modifiable factors (smoking and marked obesity) and nonmodifiable factors (having brown eyes, myopia, and high pulse pressure). Vitamin supplement use was not related to cataract. CONCLUSION These data add to the body of evidence suggesting that eating foods rich in a variety of vitamins and minerals may contribute to postponing the occurrence of the most common type of cataract in the United States.

Using Regression Calibration Equations That Combine Self-Reported Intake and Biomarker Measures to Obtain Unbiased Estimates and More Powerful Tests of Dietary Associations

The authors describe a statistical method of combining self-reports and biomarkers that, with adequate control for confounding, will provide nearly unbiased estimates of diet-disease associations and a valid test of the null hypothesis of no association. The method is based on regression calibration. In cases in which the diet-disease association is mediated by the biomarker, the association needs to be estimated as the total dietary effect in a mediation model. However, the hypothesis of no association is best tested through a marginal model that includes as the exposure the regression calibration-estimated intake but not the biomarker. The authors illustrate the method with data from the Carotenoids and Age-Related Eye Disease Study (2001--2004) and show that inclusion of the biomarker in the regression calibration-estimated intake increases the statistical power. This development sheds light on previous analyses of diet-disease associations reported in the literature.

Joint Associations of Diet, Lifestyle, and Genes with Age-Related Macular Degeneration

PURPOSE Unhealthy lifestyles have been associated with increased odds for age-related macular degeneration (AMD). Whether this association is modified by genetic risk for AMD is unknown and was investigated. DESIGN Interactions between healthy lifestyles AMD risk genotypes were studied in relation to the prevalence of AMD, assessed 6 years later. PARTICIPANTS Women 50 to 79 years of age in the Carotenoids in Age-Related Eye Disease Study with exposure and AMD data (n=1663). METHODS Healthy lifestyle scores (0-6 points) were assigned based on Healthy Eating Index scores, physical activity (metabolic equivalent of task hours/week), and smoking pack years assessed in 1994 and 1998. Genetic risk was based on Y402H in complement factor H (CFH) and A69S in age-related maculopathy susceptibility locus 2 (ARMS2). Additive and multiplicative interactions in odds ratios were assessed using the synergy index and a multiplicative interaction term, respectively. MAIN OUTCOME MEASURES AMD presence and severity were assessed from grading of stereoscopic fundus photographs taken in 2001-2004. AMD was present in 337 women, 91% of whom had early AMD. RESULTS The odds of AMD were 3.3 times greater (95% confidence interval [CI], 1.8-6.1) in women with both low healthy lifestyle score (0-2) and high-risk CFH genotype (CC), relative to those who had low genetic risk (TT) and high healthy lifestyle scores (4-6). There were no significant additive (synergy index [SI], 1.08; 95% CI, 0.70-1.67) or multiplicative (Pinteraction=0.94) interactions in the full sample. However, when limiting the sample to women with stable diets before AMD assessment (n=728) the odds for AMD associated with low healthy lifestyle scores and high-risk CFH genotype were strengthened (odds ratio, 4.6; 95% CI, 1.8-11.6) and the synergy index was significant (SI, 1.34; 95% CI, 1.05-1.70). Adjusting for dietary lutein and zeaxanthin attenuated, and therefore partially explained, the joint association. There were no significant additive or multiplicative interactions for ARMS2 and lifestyle score. CONCLUSIONS Having unhealthy lifestyles and 2 CFH risk alleles increased AMD risk (primarily in the early stages), in an or additive or greater (synergistic) manner. However, unhealthy lifestyles increased AMD risk regardless of AMD risk genotype.

Duration of Physical Activity and Serum 25-hydroxyvitamin D Status of Postmenopausal Women

PURPOSE To investigate whether the association between physical activity and serum 25-hydroxyvitamin D (25(OH)D) concentrations is independent of sun exposure, body size, and other potential explanatory variables. METHODS By using data from a sample of 1343 postmenopausal women from the Womens Health Initiative, we used linear regression to examine the associations of duration (minutes/week) of recreational activity and of yard work with 25(OH)D concentrations (nmol/L). RESULTS In age-adjusted analyses, positive associations were observed between 25(OH)D concentrations and both duration of recreational physical activity (β = 0.71, SE [0.09], p <.001) and yard work (β = 0.36, SE [0.10], p = .004). After further adjustment for vitamin D intake, self-reported sunlight exposure, waist circumference, and season of blood draw, 25(OH)D was significantly associated with recreational activity (β = 0.21, SE [0.09], p = .014) but not with yard work (β = 0.18, SE [0.09], p = .061). Interactions were observed between season and both recreational activity (P(interaction) = .082) and yard work (P(interaction) = .038) such that these activity-25(OH)D associations were greater during summer/fall compared with winter/spring. Self-reported sunlight exposure and measures of body size did not modify the associations. CONCLUSIONS The observed age-adjusted activity-25(OH)D associations were attenuated after adjusting for explanatory variables and were modified by season of blood draw. Adopting a lifestyle that incorporates outdoor physical activity during summer/fall, consuming recommended amounts of vitamin D, and maintaining a healthy weight may improve or maintain vitamin D status in postmenopausal women.

Lutein and Zeaxanthin Isomers in Eye Health and Disease

Current evidence suggests lutein and its isomers play important roles in ocular development in utero and throughout the life span, in vision performance in young and later adulthood, and in lowering risk for the development of common age-related eye diseases in older age. These xanthophyll (oxygen-containing) carotenoids are found in a wide variety of vegetables and fruits, and they are present in especially high concentrations in leafy green vegetables. Additionally, egg yolks and human milk appear to be bioavailable sources. The prevalence of lutein, zeaxanthin, and meso-zeaxanthin in supplements is increasing. Setting optimal and safe ranges of intake requires additional research, particularly in pregnant and lactating women. Accumulating evidence about variable interindividual response to dietary intake of these carotenoids, based on genetic or metabolic influences, suggests that there may be subgroups that benefit from higher levels of intake and/or alternate strategies to improve lutein and zeaxanthin status.