FNOA: Antioxidants (2011-2012)

Citation:
 
Study Design:
Class:
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Quality Rating:
Research Purpose:

Macular carotenoid pigments composed of lutein and zeaxanthin are thought to affect the development of age-related maculopathy (ARM). Macular carotenoid levels were measured in normal Japanese subjects and Japanese subjects with ARM.

Inclusion Criteria:
  • Normal group: No history of severe systemic disease such as diabetes or of heart and liver dysfunction, no eye disorders
  • ARM group: Undergoing treatment for ARM or age-related macular degeneration (AMD) after having been diagnosed previously with either early ARM or late ARM (equal to AMD) in at least one eye by a dilated retinal examination using both an ophthalmoscope and a slit-lamp with a Goldman contact lens.
Exclusion Criteria:
  • Normal Group: Those with a history of systemic disease, those who regularly used lutein supplements and those with eye disorders
  • ARM group: Patients found to have poor pupil dilation (<7mm) or other macular diseases were excluded from the study.
Description of Study Protocol:

Recruitment

Normal group: Not specified

ARM group: Subjects were recruited from patients visiting Seirei Hamarmatsu General Hospital from July through October, 2005 for treatment of ARM or AMD. 

Design

Case-Control Study 

Blinding used  

Not used

Intervention  

Not applicable

Statistical Analysis

Descriptive statistics, t-tests, and one-way analysis of variance (ANOVA) with Scheffe post hoc tests were used.

Data Collection Summary:

Timing of Measurements

July through October 2005

Dependent Variables

  • Macular carotenoid levels measured using resonance Raman spectroscopy
  • Macular pigment levels
  • Plasma lutein concentration.

Independent Variables

ARM diagnosis (ARM group)

Control Variables

  • Age
  • Tobacco smoking history
  • History of lutein supplementation.
Description of Actual Data Sample:
  • Initial N:
    • Normal group 100
    • ARM group 97
  • Attrition (final N): 
    • Normal group: None noted
    • ARM group: 187 eyes of 97 patients were examined
    • Seven eyes were excluded
  • Age: 
    • Normal group: Ages ranged 20 to 80 years (mean±standard deviation 44.9±15.9) divided into five age groups of 10 men and 10 women 20-29, 30-39, 40-49, 50-59 and >60 years of age
    • ARM group: Ages ranged 50-85 years
  • Ethnicity: Japanese
  • Other relevant demographics: 
    • Normal group: 50 men, 50 women
    • ARM group: Not specified
  • Anthropometrics: None
  • LocationHamamatsu, Japan.

 

Summary of Results:

Macular Carotenoid and Plasma Lutein Levels in Normal Subjects

  • The level of macular pigments in normal subjects ranged 363 to 2,891 Raman counts, the mean (± SD) of all subjects was 1,471±540, 1,415±422 in men and 1,527±558 in women, there was no significant difference between men and women (P=0.3, t test)
  • Macular carotenoid levels significantly declined with age (P≤0.0001, r= -0.42). The macular pigment level in subjects age 60 years and older was significantly lower then those of subjects in their twenties and forties (f=6.14; P=0.0002).
  • Plasma lutein concentrations ranged from 101 to 569ng/ml. The measurements for two subjects were considered to be measurement errors and were excluded from the study. The mean (±SD) serum lutein concentration of all subjects was 264±103ng/ml. 253±107 in men and 276±98 in women. There was no significant difference in the levels in men and women (P=0.27, t test).
  • Plasma lutein levels increased significantly with age (P≤0.0001, r=0.39). Plasma lutein concentrations in subjects in the 20 year old age group were significantly lower than those of subjects in their sixties (f=4.59; P=0.002).
  • Macular pigment levels slightly declined with increasing plasma lutein concentrations (P=0.03; r= -0.22).

Macular Carotenoid Levels in Patients with Age-Related Maculopathy: Comparison between Normal Eyes and Age-Age Maculopathy Eyes

Macular carotenoid levels were reported as the following:

 

Raman Counts

Mean±SD
Normal appearing eyes of patients with ARM in the other eye 143 to 1,094  533±318
Eyes with early ARM  71 to 1,087  620±204
Eyes with ARM 21 to 1,082  427±283
Normal subjects 60 years of age and older 652 to 1,941 1,100±340
With lutein supplementation and  with ARM  525  ±294
Without lutein supplementation and with ARM  528  ±269

The macular carotenoid levels of normal-appearing eyes of ARM patients, early ARM patients and AMD patients were significantly lower than that of normal subjects 60 year of age and older (F=36.44, P<0.0001).

Effect of Severity in the Target Eye on Macular Carotenoid Levels:

  • When early ARM was divided into four groups based on the severity scale used by the AREDS research group, the differences in macular carotenoid levels among the four groups were not significant (f=0.35, P=0.79, one-way ANOVA)
  • A relationship was found where macular carotenoid levels were lower in exudative AMD, atrophic AMD and disciform scar, but the differences among these three types was not significant (f=1.48, P=0.24, one-way ANOVA)
  • When carotenoid levels of eyes with occult, minimally classic and predominantly classic choroidal neovascularization (CNV) were examined, there was no significant difference among CNV types (f=0.28, P=0.84, one-way ANOVA)
  • There was not significant difference between eyes with CNV and polypoidal choroidal vasculopathy (PCV) (f=1.8, P=0.18, one-way ANOVA). 

Effect of Severity in the Opposite Eye on Macular Carotenoid Levels:

  • The macular carotenoid levels in the normal-appearing fellow eyes of patients with ARM in the other eye were affected by the severity of the diseased eye (f=12.10, P=0.0001, one-way ANOVA with Scheffe's post hoc test)
  • The average for the normal-appearing fellow eyes with AMD in the opposite eye was significantly lower than that in subjects with two normal eyes. Macular carotenoid levels in early ARM with normal appearance of the opposite eye, early ARM with early ARM in the opposite eye and early ARM with AMD in the opposite eye were found to be lower in that order although the differences among those three groups were not statistically significant (f=0.38, P=0.68, one-way ANOVA).

Effect of Treatment on Macular Carotenoid Levels in Age-Related Maculopathy:

  • The mean ± pigment levels of eyes without prior treatment were 396±267 and those eyes that had received prior treatment were 457±295
  • No significant differences between eyes with and without prior treatment (P=0.56, t test) or among treatment methods (f=1.11, P=0.35, one-way ANOVA) was found.

Effect of Macular Thickness on Macular Carotenoid Levels:

No remarkable correlation between carotenoid levels and macular thickness was found (P=0.36, r= -0.08).

Effect of Visual Acuity on Macular Carotenoid Levels:

The pigment levels were found to be higher in eyes with better visual acuity (P=0.49; P<0.0001, Spearman rank test).

 

 

Author Conclusion:

This study confirmed that macular carotenoid levels decrease with age. In other studies with mainly white subjects, Raman counts declined exponentially. In this study, the decrease in Japanese persons was linear. The reason for this was unclear.

Carotenoid levels varied considerably in subjects younger than 50 years of age in this study. The reason for this variation is unclear. Two possible explanations are a difference in consumption of green vegetables and other carotenoid containing foods or because the amount of receptor protein for lutein and zeaxanthin differs among young people. Also, subjects with higher levels may have a considerable decrease in levels with age because the lowest level of macular carotenoid was constant in all ages.

Plasma lutein concentrations increased with age in Japanese subjects. The reason why macular carotenoid levels in older subjects were low, although plasma lutein levels were found to be high is unclear.  It may be possible that receptors for carotenoids in the retina may decline in older subjects. Additional studies are needed to explore the relationship between carotenoids and AMD.

This study showed that macular carotenoid levels in ARM patients were significantly lower than those in healthy volunteers older then 60 years of age in the Japanese population, which agrees with a previous study in white persons and a pathological study of donors with a history of AMD.  

The macular carotenoid levels found in late ARM (AMD) were significantly lower than those found in early ARM. This suggests that the macular carotenoid levels may decline with the progression of ARM. More detailed analysis in the study found the possibility that macular carotenoids may be one of the causes of ARM. It was also implied that lower carotenoid levels may be one of the risk factors of ARM progression.  Additional studies are needed to determine conclusively the role of macular carotenoids as a cause of ARM. Type of CNV, treatment and retinal thickness had no influence on macular carotenoid levels. 

Overall, further investigation is still needed to determine whether low macular carotenoid levels are a risk factor of the progression ARM, but if so, the prophylactic or therapeutic effect of lutein and zeaxanthin supplementation may continue to be promising.

Funding Source:
University/Hospital: Seirei Hamamatsu General Hospital
Reviewer Comments:

The authors noted the following limitations:

  • Although, sensitivity, specificity and repeatability of resonance Raman spectroscopy has been confirmed in previous reports, this method has some limitations with measurements  for subjects with severe visual disturbance 
  • Also, the presence of cataracts was found to affect the measurements, so patients with nuclear cataract of more than stage 4/7 of AREDS classification, apparent cortical opacity or any subscapular opacity were excluded from the study. However, there still may have been some bias from the presence of cataract because no statistical analysis regarding the presence of cataracts was done.
  • When comparing carotenoid levels between white and Japanese persons, the carotenoid levels of Japanese persons seemed to be higher than those of white subjects. The sensitivity for detecting Raman scattering of the instrument used in this Japanese study was higher than that used in the study of white persons. In the future, to compare Japanese and white macular pigment levels, it will be necessary to use the same instrument or have the instruments carefully cross calibrated.
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) N/A
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) N/A
 
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? ???
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) Yes
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? Yes
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? Yes
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? N/A
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? N/A
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? N/A
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? ???
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? N/A
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? ???
  7.5. Was the measurement of effect at an appropriate level of precision? ???
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes