ELECTROCARDIOGRAPHIC CONDUCTION DISTURBANCES IN ASSOCIATION WITH LOW-LEVEL LEAD-EXPOSURE (THE NORMATIVE AGING STUDY)

Recent research indicates that cumulative exposure to lead may be more toxic than previously thought. This was undertaken to examine the rel ation of low-lead exposure to electrocardiographic (ECG) conduction di sturbances among 775 men who participated in the Normative Aging Study (average age 68 years; range 48 to 93). We used K-x-ray fluorescence to measure lead levels in the tibia and patella, and graphite furnace atomic absorption spectroscopy to measure blood lead levels. The mean (SD) values for blood lead, tibia lead, and patella lead were 5.8 (3.4 ) mu g/dl, 22.2 (13.4) mu g/g, and 30.8 (19.2) mu g/g, respectively. B one lead levels were found to be positively associated with heart rate -corrected QT and QRS intervals, especially in younger men. Specifical ly, in men <65 years of age, a 10 mu g/g increase in tibia lead was as sociated with an increase in the QT interval of 5.03 ms (95% confidenc e interval [CI], 0.83 to 9.22) and with an increase in the QRS interva l of 4.83 ms (95% CI, 1.83 to 7.83) in multivariate regression models. In addition, an elevated bone lead level was found to be positively a ssociated with an increased risk of intraventricular block in men <65 years of age and with an increased risk of atrioventricular (AV) block in men greater than or equal to 65 years of age. After adjustment for age and for serum high-density lipoprotein (HDL) level, a 10 mu g/g i ncrease in tibia lead was associated with an odds ratio (OR) of 2.23 ( 95% CI, 1.28 to 3.90) for intraventricular block in men <65 years of a ge and with an OR of 1.22 (95% CI, 1.02 to 1.47) for AV block in men g reater than or equal to 65 years of age. Blood lead level was not asso ciated with any of the ECG outcomes examined. The results suggest that cumulative exposure to lead, even at low levels, may depress cardiac conduction. (C) 1998 by Excerpta Medica, Inc.