Back pain claim rates in Japan and the United States: framing the puzzle.

STUDY DESIGN

This is a cross-national comparison of workers' compensation claims for back pain in Japan and the United States (US).

OBJECTIVES

The main objective is to juxtapose rates of back pain claims in Japan and Washington state. Because the Washington state rate closely matches rates for other US states as well as the rate for the US as a whole, it is used to represent the US rate. A puzzle is to be framed: Why are back pain claim rates in Japan and the United States so disparate?

SUMMARY OF BACKGROUND DATA

Occupational back pain is common among workers in both Japan and the United States. Wage compensation for time off work is also substantial in both countries and potentially induces time off work at least as much in Japan as in the United States. Accordingly, back pain claim rates in Japan seemingly would be on the same order of magnitude as rates in the United States.

METHODS

Washington state rates are based on data from its state fund. Both Japan and Washington state rates are composed of the number of workers eligible to file worker compensation claims in a given year (denominator) and the number of back pain claims accepted during that year (numerator). Because rates may fluctuate from year-to-year, 5 years of data on rates are presented, 1995-1999. Central to the comparison are Japanese and Washington state rates of workers' compensation claims for back pain with more than 3 days compensated time loss from work.

RESULTS

The back pain claim rate in 1999 was 60 times higher in Washington state than in Japan. The disparity in rates for the other years in the study (1995-1998) was similar.

CONCLUSION

Back pain is common among workers both in Japan and the United States, but there is no simple or necessary relationship between that symptom and how it manifests itself in one country or another. Rather, the symptom is protean in its social manifestations. As for what shapes those manifestations-or, more specifically, what causes the startling disparity in back pain claim rates between Japan and the United States-that is a puzzle. Various solutions to the puzzle are discussed, but it remains essentially unsolved.