Smoking habit is associated with diabetic macular edema in Type 1 diabetes mellitus patients

Abstract

Diabetic macular edema (DME) affects up to 29% of patients with diabetic retinopathy (DR) and is the most frequent cause of visual impairment in these patients (Klein, Klein, Moss, Davis, & DeMets, 1984). However, risk factors for DME have not been fully established. Recently, Romero et al. (2007) prospectively studied 112 type 1 diabetes mellitus (DM) patients (age 39.9±10.5 years; DM duration 23.4±7.5 years; 48.2% males) to evaluate risk factors for DME. After 15 years, the incidence of DME was 20.5%. In logistic multivariate regression models, adjusted for gender and age, A1c test and low-density lipoprotein (LDL) cholesterol levels, arterial hypertension, macroangiopathy, severity of retinopathy, and macroalbuminuria were the recognized risk factors for DME. In a cross-sectional study, we evaluated 224 Type 1 DM patients aged 33.3±13.9 years, with 16.5±9.6 years of DM duration (105 males) regularly attending the DM outpatient clinic at Hospital de Clinicas de Porto Alegre, Porto Alegre, Rio Grande do Sul, Brazil. A complete clinical evaluation was performed as previously described (Leitao et al., 2007). DME was defined as one or more of the following: any retinal thickening within 500 μm of the center of the macula, with or without loss of retinal transparency; hard exudates associated with retinal thickening within 500 μm of the center of the macula; or one disc area of thickening within one disc diameter of the center of the macula (ETDRS, 1985). Twenty-four percent of the patients had nonproliferative DR (mild, n=38; moderate, n=9; severe, n=7), and 20.7 % (n=46) proliferative DR. The prevalence of DME was 9.4% (n=21). In univariate analysis, patients with DME had higher levels of urinary albumin excretion (UAE) [26.2 mg/dl (0.1–1105) vs. 8.7 (0.1– 71110), P=.049] than those without it. DM duration, body mass index, blood pressure levels, glycemic (A1c test) and lipid profile (total, LDL, and high-density lipoprotein cholesterol and triglycerides) did not differ between groups. Current or former smoking habit (50% vs. 25%; P=.034) and diabetic nephropathy (micro- and macroalbuminuria) (58.8% vs. 29.5%; P=.026) were more frequent in patients with than those without DME. The severity of DR was also associated with DME (P for trend .027). In logistic multivariate regression analysis, with the presence of DME as the dependent variable and DM duration, smoking habit, systolic blood pressure, A1c test, and UAE as independent ones, only the smoking habit was associated with DME (OR 2.02, 95%CI 1.01–4.00; P=.04). Differences between our results and those of Romero et al., besides study design, could be explained by the younger age and shorter DM duration of our patients: a difference of about 6 years of age [6.6 years (95% CI 3.6–9.5; Pb.0001)] and of 7 years of DM duration [6.9 years (95% CI 4.7-8.9; Pb.0001)]. The present data demonstrated that, besides glycemic, lipid, and blood pressure control, the smoking habit, a nontraditional DME risk factor, should also be taken into account in order to prevent it. To our knowledge, this is the first report of this association.