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White-collar workers may face an unexpected occupational risk, CDC researchers suggested: increased mortality from amyotrophic lateral sclerosis (ALS) and Parkinson's disease.

For ALS, the strongest links were with careers in computers/mathematics, architecture/engineering, legal, and education/training/library, while Parkinson's ties were strongest for community/social services, education/training/library, and legal occupations, John Beard, PhD, of the CDC, and colleagues .

"If the associations between higher socioeconomic status (SES) occupations and ALS and Parkinson's disease are real, then the burdens of ALS and Parkinson's mortality could also increase in the future because the U.S. workforce is increasing in the number and proportion of workers employed in higher SES occupations," they wrote.

The only consistently reported risk factors for ALS have been increasing age, male sex, and smoking. For Parkinson's the list includes increasing age, male sex, and pesticide exposure; smoking and caffeine intake are inversely associated. There's been less study of the role of occupation in these diseases, the researchers said. (Findings on a possible link to farm work have been inconsistent.)

So Beard and colleagues looked at National Occupational Mortality Surveillance (NOMS) data, which includes more than 12 million deaths from 30 U.S. states. Their study involved 26,917 ALS deaths, 115,262 Parkinson's deaths, and 158,618 deaths from chronic disease of the endocardium.

Overall, they found occupations associated with higher socioeconomic status were overrepresented for ALS and Parkinson's disease.

In ALS, the proportionate mortality ratios (PMRs) for 14 job types were significantly above 1.0, and for four -- computer and mathematical, architecture and engineering, legal, and education/training/library -- PMRs were 1.5 or above. The highest was for education/training/library careers (PMR 1.67, 95% CI 1.58 to 1.76). Higher ratios were also seen for business operations, management, financial, life sciences, and legal careers.

In Parkinson's, PMRs for 13 careers were significantly above 1.0, though none were above 1.50. The highest was for community and social services jobs (PMR 1.48, 95% CI 1.41 to 1.56), followed by education/training/library (1.46, 95% CI 1.43 to 1.50).

By comparison, among endocardium-related deaths, mortality ratios for only 9 job types were above 1.0, and the magnitude of the associations were much smaller than those seen for ALS and Parkinson's, the researchers reported.

Beard and colleagues noted that the findings are unusual in that the highlighted occupations aren't normally associated with exposure to potential neurotoxins such as pesticides, solvents, lead, welding fumes, or strong electromagnetic fields.

A shift in the U.S. workforce toward older people working in higher socioeconomic status jobs may explain the findings, but the full story remains to be untangled in larger studies, they concluded.

Also noteworthy is that the study only examined mortality rather than disease incidence; possibly, blue-collar workers do develop these conditions at similar rates but die from other causes. A related limitation is that cause of death in the NOMS database comes from death certificates.