Amyotrophic lateral sclerosis and occupational history. A pilot case-control study.

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.

Physical activity, trauma, and ALS: a case-control study.

AIMS: The association of trauma and physical activity with ALS is controversial. We explored the relation in a pilot case-control study. MATERIAL AND METHODS: ALS patients were selected from a university muscle disease clinic and paired with two matched controls: one from the clinic, but having different diseases, and one from the community. RESULTS: We found several strong and statistically significant differences between ALS cases and the matched controls. These included severe head, neck and back injury (OR = 5.3), the frequency of sweating in work (OR = 1.6) or leisure activity (also OR = 1.6), and earning a school letter (OR = 3.1). Other measures of trauma and activity, while not achieving statistical significance (p < 0.05), were in accord with these findings. DISCUSSION: Possible explanations include trauma and vigorous exercise precipitating ALS; trauma as an early sign of disease; or a third factor associated with ALS predisposing to injury. CONCLUSIONS: Severe head, neck, and back injury and frequency of sweating both in work and leisure activity showed a strong association with ALS. Further study could test narrower and less common exposures with greater statistical power.