Further evaluation of docosahexaenoic acid in patients with retinitis pigmentosa receiving vitamin A treatment: subgroup analyses.
OBJECTIVE
To determine whether docosahexaenoic acid will slow the course of retinal degeneration in subgroups of patients with retinitis pigmentosa who are receiving vitamin A.


METHODS
A cohort of 208 patients with retinitis pigmentosa, aged 18 to 55 years, were randomly assigned to 1200 mg of docosahexaenoic acid plus 15 000 IU/d of vitamin A given as retinyl palmitate (DHA + A group) or control fatty acid plus 15 000 IU/d of vitamin A (control + A group) and followed up over 4 years. Seventy percent of the patients in each group were taking vitamin A, 15 000 IU/d, prior to entry. We compared rates of decline in ocular function in the DHA + A vs control + A groups among the subgroups defined by use or nonuse of vitamin A prior to entry. We also determined whether decline in ocular function was related to red blood cell phosphatidylethanolamine docosahexaenoic acid level, dietary omega-3 fatty acid intake, or duration of vitamin A use. Main outcome measures were Humphrey Field Analyzer visual field sensitivity, 30-Hz electroretinogram amplitude, and visual acuity.


RESULTS
Among patients not taking vitamin A prior to entry, those in the DHA + A group had a slower decline in field sensitivity and electroretinogram amplitude than those in the control + A group over the first 2 years (P =.01 and P =.03, respectively); these differences were not observed in years 3 and 4 of follow-up or among patients taking vitamin A prior to entry. In the entire cohort, red blood cell phosphatidylethanolamine docosahexaenoic acid level was inversely related to rate of decline in total field sensitivity over 4 years (test for trend, P =.05). This was particularly evident over the first 2 years among those not on vitamin A prior to entry (test for trend, P =.003). In the entire control + A group, dietary omega-3 fatty acid intake was inversely related to loss of total field sensitivity over 4 years (intake, <0.20 vs > or =0.20 g/d; P =.02). The duration of vitamin A supplementation prior to entry was inversely related to rate of decline in electroretinogram amplitude (P =.008).


CONCLUSIONS
For patients with retinitis pigmentosa beginning vitamin A therapy, addition of docosahexaenoic acid, 1200 mg/d, slowed the course of disease for 2 years. Among patients on vitamin A for at least 2 years, a diet rich in omega-3 fatty acids (> or =0.20 g/d) slowed the decline in visual field sensitivity.
Berson
Eliot L
EL
Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School, 243 Charles Street, Boston, MA 02114, USA.
Rosner
Bernard
B
Sandberg
Michael A
MA
Weigel-DiFranco
Carol
C
Moser
Ann
A
Brockhurst
Robert J
RJ
Hayes
K C
KC
Johnson
Chris A
CA
Anderson
Ellen J
EJ
Gaudio
Alexander R
AR
Willett
Walter C
WC
Schaefer
Ernst J
EJ
D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D004281:Docosahexaenoic Acids / Q000378:metabolism / Q000627:therapeutic use*; D004311:Double-Blind Method; D004359:Drug Therapy, Combination; D004596:Electroretinography; D004910:Erythrocyte Membrane / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010714:Phosphatidylethanolamines / Q000378:metabolism; D012160:Retina / Q000503:physiopathology; D012174:Retinitis Pigmentosa / Q000188:drug therapy* / Q000503:physiopathology; D014786:Vision Disorders / Q000188:drug therapy / Q000503:physiopathology; D014794:Visual Fields / Q000502:physiology; D014810:Vitamin E / Q000627:therapeutic use*
D010714:Phosphatidylethanolamines; D014810:Vitamin E; D004281:Docosahexaenoic Acids; C483858:phosphatidylethanolamine