Table 2.

Mean daily working hours of 195 Japanese men with acute myocardial infarction and 331 controls matched for age and occupation during the two months before infarction and in the months with the shortest and longest mean working hours in the year before infarction, and changes in mean daily working hours between each pair of months

	Mean (SE) working hours
	Cases (n=195)	Controls (n=331)	P value
Mean daily working hours during a month*
A: Last month before infarction	9.13 (0.22)	9.24 (0.21)	0.53
B: Month before last	8.95 (0.23)	9.27 (0.21)	0.084
C: Month with shortest mean working hours	7.45 (0.21)	8.17 (0.19)	0.0001
D: Month with longest mean working hours	10.03 (0.28)	10.26 (0.26)	0.31
Change in mean daily working hours
A−B	0.18 (0.11)	−0.03 (0.10)	0.018
A−C	1.68 (0.18)	1.08 (0.17)	0.0001
A−D	−0.90 (0.20)	−1.02 (0.19)	0.48
D−C	2.58 (0.26)	2.09 (0.25)	0.022

^*Adjusted for age and occupation categories by using analysis of covariance.