## 3 Results
### Distribution and Sick Leave Days of Low Back MSDs and Factors Associated with Low Back MSDs
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Variable**} & \multicolumn{2}{c}{**Total**} & \multirow{2}{*}{**Low Back MSDs**} & \multicolumn{2}{c}{**Sick Leave Days**} & \multicolumn{2}{c}{**Logistic Regression on Low Back**} \\  & & \(N\) & \(n\) & \% & \(n\)/N & **Mean** & **SD** & **OR** & **[95\% CI]** & \(p\)** \\ \hline Occupation & 985 & 323 & 100\% & 32.8\% & 279.5 & 186.7 & & & 0.014 \({}^{*}\) \\ Welder (Ref) & 183 & 73 & 22.6\% & 39.9\% & 290.3 & 144.4 & & & & 0.014 \({}^{*}\) \\ Fitter & 189 & 50 & 15.5\% & 26.5\% & 287.1 & 154.3 & 0.624 & 0.327 & 1.191 & 0.153 \\ Electrician/plumber & 259 & 89 & 27.6\% & 34.4\% & 265.4 & 184.8 & 0.662 & 0.379 & 1.155 & 0.147 \\ Painter & 100 & 22 & 6.8\% & 22.0\% & 281.6 & 196.1 & 0.402 & 0.186 & 0.867 & 0.020 \({}^{*}\) \\ Grinding worker & 43 & 7 & 2.2\% & 16.3\% & 330.1 & 273.1 & 0.236 & 0.075 & 0.737 & 0.013 \({}^{*}\) \\ Crane operator & 54 & 17 & 5.3\% & 31.5\% & 298.0 & 223.0 & 0.336 & 0.145 & 0.779 & 0.011 \({}^{*}\) \\ Installer & 157 & 65 & 20.1\% & 41.4\% & 269.7 & 231.9 & 0.988 & 0.523 & 1.867 & 0.971 \\ Age (years) & & \(\chi^{2}=23.845\), \(p=0.001\)\({}^{*}\) & & & & & & 0.001 \({}^{*}\) \\ \(<\)40 (Ref) & 238 & 140 & 43.3\% & 58.8\% & 244.0 & 159.2 & & & & 0.001 \({}^{*}\) \\
40–49 & 267 & 98 & 30.3\% & 36.7\% & 297.6 & 160.1 & 0.351 & 0.214 & 0.573 & 0.001 \({}^{*}\) \\
50–59 & 289 & 56 & 17.3\% & 19.4\% & 305.8 & 258.5 & 0.190 & 0.112 & 0.322 & 0.001 \({}^{*}\) \\ \(\geq\)60 & 191 & 29 & 9.0\% & 15.2\% & 338.6 & 206.1 & 0.195 & 0.104 & 0.366 & 0.001 \({}^{*}\) \\ \(\chi^{2}=125.504\), \(p<0.001\)\({}^{*}\) & & & & & & & & 0.001 \({}^{*}\) \\ MSD type & & & & & & & & & 0.001 \({}^{*}\) \\ Sprain (Ref) & 209 & 65 & 20.1\% & 31.1\% & 114.4 & 154.8 & & & & 0.001 \({}^{*}\) \\ Hernatated disc & 380 & 258 & 79.9\% & 67.9\% & 321.1 & 170.5 & 5.299 & 3.522 & 7.971 & 0.001 \({}^{*}\) \\ Rupture & 396 & 0 & 0.0\% & 0\% & & & & & & \(\cdot\) \\  & &According to company size, companies with \(\geq\)1000 workers had the most frequent low back MSDs (54.5%), followed by companies with 100-999 workers (21.7%). According to company size, there was a significant difference in frequency distributions between low back MSDs and the other MSDs (\(\chi^{2}\) = 19.894, \(p\) \(<\) 0.001). The ratio of low back MSDs among total MSDs was the highest at companies with \(<\)30 workers (48.4%). The mean of sick leave days for low back MSDs was the highest at companies with 30-99 workers (318.4 days). The share of low back MSDs is high as the share of total MSDs of large companies, but the ratio of low back MSDs is the highest in small companies with \(<\)30 workers. Table 3 also shows the result of the binary logistic regression analysis on the low back. The factors significantly associated with low back MSDs were company size, occupations, age, and MSD type (classification table value = 83.7%). The logistic regression model was tested by the G value of the model coefficient (\(\chi^{2}\) = 598.731, \(p\) \(<\) 0.001). The explanatory power of the dependent variable was the Nagelkerke value (0.634), and the fitness test for the variable was the Hosmer and Lemeshow value (\(\chi^{2}\) = 8.224, \(p\) = 0.412 \(>\) 0.05). Therefore, it was found that the model and explanatory power were suitable. Looking at the occupation type, the possibility that the welders will be confirmed as having low back MSDs is higher than that of the grinding workers (4.237 times, 95% CI = (1.357, 13.333)), crane operators (2.979 times, 95% CI = (1.284, 6.897)), or painters (2.488 times, 95% CI = (1.153, 5.376)). In terms of age, the likelihood that workers \(<\)40 years will be confirmed as having a low back MSD is higher than that of workers \(\geq\) 60 years old (5.128 times, 95% CI = (2.732, 9.615)), 50-59 years (5.263 times, 95% CI = (3.106, 8.929)), or 40-49 years (2.849 times, 95% CI = (1.745, 4.673)). In terms of MSD type, the possibility that a herniated disc will be confirmed as a low back MSD is 5.299 times (95% CI = (3.522, 7.971)) higher than that of a sprain.