Association of Cigarette Smoking With Diabetic Retinopathy
Objective: To determine whether cigarette smoking is associated with the incidence and progression of diabetic retinopathy. Research Design and Methods: Younger-onset diabetic subjects who had been diagnosed at 30 yr of age and having their diagnosis confirmed by a casual or postprandial serum glucose level of at least 11.1 mM or a fasting serum glucose level of at least 7.8 mM on at least two occasions and is referred to as older onset. There were 5431 subjects who met the eligibility criteria, of whom 2341 had had diabetes for 15 yr. A random sample of 576 subjects from the first group, 579 subjects from the second group, and 625 subjects from the third duration group were selected for examination. There were no significant differences (P > 0.10) between the 1780 selected and 3651 unselected subjects with respect to age, age at diagnosis, blood pressure, sex, or type of hypoglycemic medications. No previous knowledge of retinopathy status was available during the selection process. The older-onset group was further divided into subjects taking insulin (n = 824) and those not taking insulin (n = 956). In the younger-onset group, 996 (82.3%) participated in the baseline examination, and in the older-onset group 1370 (77%) participated, of whom 674 were taking insulin and 696 were not taking insulin. For this analysis, the younger-onset group was restricted to those who were 2:18 yr of age at the baseline examination (n = 799). The surviving subjects were invited to participate in a 4-yr follow-up examination from 1984 to 1986. Both the baseline and follow-up examinations followed a similar protocol. This consisted of obtaining informed consent; measuring blood pressure; measuring refractive error and best-corrected visual acuity for distance with the Early Treatment Diabetic Retinopathy Study protocol (27); performing a slit-lamp examination for chamber depth and presence of iris neovascularization; measuring intraocular pressure; dilating the pupils; administering a medical history questionnaire including items on cigarette smoking history; examining the lenses for cataracts; performing an ophthalmoscopic examination; taking stereoscopic color fundus photographs of seven standard fields and a nonstereoscopic red reflex photograph for each eye; determining urine glucose, ketone, and protein levels; and determining blood glucose and glycosylated hemoglobin values.
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To determine diabetic retinopathy status at both the baseline and follow-up examinations, all fundus photographs were graded with the modified Airlie House classification scheme, as further adapted for the WESDR follow-up examination (28,29). Level 10 represents no retinopathy, levels 21-51 represent nonproliferative retinopathy of increasing severity, and levels 60-80 represent proliferative retinopathy of increasing severity. Retinopathy level for a subject was derived by giving the eye with the higher level greater weight. Subjects in a given level were divided into two groups: those with this level in each eye and those with a lesser level in one eye. For example, the level for a participant with level 31 retinopathy in each eye was specified by the notation level 31/31. This scheme provides an 11 -step scale (10/10, 21 / < 2 1 , 21/21, 31 / < 3 1 , 31/31, 41 / < 4 1 , 41/41, 51/
Objective: To determine whether cigarette smoking is associated with the incidence and progression of diabetic retinopathy. Research Design and Methods: Younger-onset diabetic subjects who had been diagnosed at 30 yr of age and having their diagnosis confirmed by a casual or postprandial serum glucose level of at least 11.1 mM or a fasting serum glucose level of at least 7.8 mM on at least two occasions and is referred to as older onset. There were 5431 subjects who met the eligibility criteria, of whom 2341 had had diabetes for 15 yr. A random sample of 576 subjects from the first group, 579 subjects from the second group, and 625 subjects from the third duration group were selected for examination. There were no significant differences (P > 0.10) between the 1780 selected and 3651 unselected subjects with respect to age, age at diagnosis, blood pressure, sex, or type of hypoglycemic medications. No previous knowledge of retinopathy status was available during the selection process. The older-onset group was further divided into subjects taking insulin (n = 824) and those not taking insulin (n = 956). In the younger-onset group, 996 (82.3%) participated in the baseline examination, and in the older-onset group 1370 (77%) participated, of whom 674 were taking insulin and 696 were not taking insulin. For this analysis, the younger-onset group was restricted to those who were 2:18 yr of age at the baseline examination (n = 799). The surviving subjects were invited to participate in a 4-yr follow-up examination from 1984 to 1986. Both the baseline and follow-up examinations followed a similar protocol. This consisted of obtaining informed consent; measuring blood pressure; measuring refractive error and best-corrected visual acuity for distance with the Early Treatment Diabetic Retinopathy Study protocol (27); performing a slit-lamp examination for chamber depth and presence of iris neovascularization; measuring intraocular pressure; dilating the pupils; administering a medical history questionnaire including items on cigarette smoking history; examining the lenses for cataracts; performing an ophthalmoscopic examination; taking stereoscopic color fundus photographs of seven standard fields and a nonstereoscopic red reflex photograph for each eye; determining urine glucose, ketone, and protein levels; and determining blood glucose and glycosylated hemoglobin values.
120
To determine diabetic retinopathy status at both the baseline and follow-up examinations, all fundus photographs were graded with the modified Airlie House classification scheme, as further adapted for the WESDR follow-up examination (28,29). Level 10 represents no retinopathy, levels 21-51 represent nonproliferative retinopathy of increasing severity, and levels 60-80 represent proliferative retinopathy of increasing severity. Retinopathy level for a subject was derived by giving the eye with the higher level greater weight. Subjects in a given level were divided into two groups: those with this level in each eye and those with a lesser level in one eye. For example, the level for a participant with level 31 retinopathy in each eye was specified by the notation level 31/31. This scheme provides an 11 -step scale (10/10, 21 / < 2 1 , 21/21, 31 / < 3 1 , 31/31, 41 / < 4 1 , 41/41, 51/
