Changes in occupational physical loading during the lifetimes of Finnish men.
OBJECTIVE
The aims of this study were to compare summary measures for occupational physical loading based on different periods of work history and to describe how loading exposures change with age and vary by age group.


METHODS
Detailed work histories reported by 232 men, aged 35-69 years, were used to compare loading in the current, longest, and heaviest jobs and a lifetime measure and to graph changes in loading over time.


RESULTS
The longest job was the best surrogate for lifetime loading (correlation coefficient 0.90). The heaviest work tended to occur in the men's teens and early twenties. For older men, the current or longest job was a poor substitute for the job with the heaviest loading (correlation coefficients 0.24, 0.28). There appeared to be both a cohort and a period effect for sedentary work, lifting and time spent in twisted or bent positions, but not for driving.


CONCLUSIONS
If the true risk for back problems is not limited to current activities, exposure misclassification may occur in many studies.
D000328:Adult; D000367:Age Factors; D000368:Aged; D015331:Cohort Studies; D005387:Finland; D006801:Humans; D008297:Male; D008875:Middle Aged; D005082:Physical Exertion; D013997:Time Factors; D014937:Work / Q000639:trends*