Amyotrophic lateral sclerosis and occupational history. A pilot case-control study
D. Strickland, S. A. Smith, G. Dolliff, L. Goldman and R. I. Roelofs
Division of Epidemiology, School of Public Health, University of Minnesota, USA.
OBJECTIVE: To assess the association of a number of occupational and
industrial exposures with amyotrophic lateral sclerosis (ALS). DESIGN: A
case-control study of ALS cases matched by age and sex to 2 controls each:
1 from a neurologic clinic and 1 from a local community. Exposures were
ascertained by questionnaire, and patients were requested before the
interview to be to prepared to supply occupational histories. SETTING:
Patients with ALS were enrolled at the University of Minnesota ALS Clinic
in Minneapolis. PATIENTS: Patients with ALS (n = 25) were from the
University of Minnesota ALS clinic, and clinic controls (n = 25) were
patients with other neuromuscular diseases from the university's Muscle
Disease Clinic, selected on the basis of clinic enrollment date nearest to
that of the matched case. Clinic controls were principally patients with
myopathies. Community controls (n = 25) were selected from the community
using a random-digit-dialing protocol matching on the first 5 digits of the
case patient's telephone number. RESULTS: The strongest association with
disease was exposure to welding or soldering materials (odds ratio, 5.0)
and the welding industry (odds ratio, 5.3). Electric plating showed a high
odds ratio of 8 (95% confidence interval, 0.9-72.0), but low statistical
significance (P < .07) Several exposures or industries, while not
statistically different, showed enough difference that to ignore them might
lead to a Type II error, a result of the pilot nature and small sample
size. These included paint or pigment manufacturing, the petroleum
industry, the printing industry, and shipbuilding. CONCLUSIONS: The
association with welding, soldering, and the welding industry is strong and
suggests a need for further work. This is despite the small numbers
studied, thus making most industrial or occupational exposures too limited
to draw conclusions or detect associations. Perhaps the most obvious
candidate from the welding, soldering exposure for a common toxin would be
lead. Other suggestions of risk were seen for paint or pigment manufacture,
shipbuilding, electric plating, and the dairy industry. The degree of
association for these, while high, is not statistically significant, and
suggests that there may be 1 or more environmental toxins common to those
industries that need more precise measurement.
