So BMC Public Health 2012, 12:258 http://www.biomedcentral.com/1471-2458/12/258 Page 5 of 7 p Table 2 The multivariate logistic regression analysis for school records in relation to the PA patterns Case OR 95% CI Boys 39,612 Academic performance ≥ Average (yes/no) No vigorous PA 7,314 Reference Once a week 7,067 1.029 0.925–1.145 0.602 Twice a week 7,847 1.198 1.080–1.329 0.001** Thrice a week 6,994 1.287 1.156–1.433 <0.001*** 4 times a week 3,066 1.265 1.117–1.433 <0.001*** 5 times a week or more 7,324 0.886 0.801–0.981 0.020* No moderate PA 7,946 Reference Once a week 8,379 1.121 1.021–1.232 0.017* Twice a week 8,351 1.337 1.216–1.471 <0.001*** Thrice a week 6,401 1.460 1.315–1.621 <0.001*** 4 times a week 2,539 1.363 1.183–1.570 <0.001*** 5 times a week or more 5,996 1.135 1.013–1.271 0.029* No strengthening exercises 13,290 Reference Once a week 8,413 0.968 0.894–1.048 0.423 Twice a week 6,354 1.076 0.978–1.183 0.132 Thrice a week 4,804 1.021 0.920–1.132 0.700 4 times a week 1,966 0.910 0.785–1.054 0.209 5 times a week or more 4,785 0.828 0.754–0.910 <0.001*** Girls 35,454 Academic performance ≥ Average (yes/no) No vigorous PA 15,676 Reference Once a week 7,540 1.074 0.988–1.168 0.094 Twice a week 5,628 0.958 0.869–1.057 0.396 Thrice a week 3,661 0.943 0.832–1.069 0.361 4 times a week 1,009 1.073 0.879–1.309 0.488 5 times a week or more 1,940 1.532 1.336–1.757 <0.001*** No moderate PA 13,059 Reference Once a week 8,640 1.034 0.947-1.129 0.455 Twice a week 6,471 1.113 1.008–1.229 0.035* Thrice a week 4,032 1.306 1.161–1.468 <0.001*** 4 times a week 1,164 1.065 0.893–1.270 0.481 5 times a week or more 2,088 0.904 0.797–1.024 0.111 No strengthening exercises 21,540 Reference Once a week 7,045 0.995 0.922–1.075 0.906 Twice a week 3,286 0.928 0.834–1.034 0.176 Thrice a week 1,898 0.997 0.867–1.147 0.969 4 times a week 564 0.764 0.579–1.009 0.058 5 times a week or more 1,121 0.739 0.618–0.883 0.001** OR, Odd Ratio; CI, Confidence Interval; PA, Physical Activity. *p < 0.05 **p < 0.01 ***p < 0.001 tested by multivariate logistic regression analysis (adjusted for age, body mass index, parents’ education level, family income status). recorded by the students themselves. Therefore, these data might be inaccurate. Second, this study did not in- vestigate whether PA might affect attention and alertness at school. Therefore, further studies will be required to determine the extent to which these variables might con- tribute to attention and alertness in students. Third, the academic performance variable did not incorporate be- havioral conduct or attendance at school, and these