Int. J. Environ. Res. Public Health2021, 18, 9171 5of 15 Table1. Distribution of handedness in our study population. N % Total 70 100 Left 6 8.57 Leftmixed 6 8.57 Right 55 78.57 Right mixed 3 4.29 For analytic purposes, left- and right-handed subjects were put together with their corresponding mixed types. Measurements referring to the right or left body side were analyzed as referring to the primary or to the non-primary hand in order to evaluate the effect of handedness. Instead of distinguishing between right- and left-handedness, we used the parameter dominant/non-dominant hand for further analysis. Mean values and standard deviations (SD) in brackets were described with approximately normally distributed continuous data. Median and interquartile ranges in brackets were shown for non-normally distributed continuous data [31]. We calculated absolute and relative frequencies for categorical variables. Numerators and denominators of the calculations were always given in parenthesis when reporting percentages in categorical data. As the study sample of 70 individuals might lack power to detect small effects, the regression results were considered with caution. The classic 5.0% significance level did not seem appropriate for exploration purposes, so effects showing higher p-values were closely considered. A threshold of 0.1 was applied in this analysis as it seemed to be useful to show the correlations between the endpoints in a comprehensible way, although any other threshold might also be appropriate. This procedure followed our aim to understand the contributors to clinical endpoints for future studies rather than providing evidence for correlations in our study sample. SAS software version 9.4 with Enterprise Guide 7.1 GUI (SAS Institute, Cary, NC, USA) was used for analyses. 3. Results 3.1. Recruitment and Baseline Characteristics The total population consisted of 63 persons in group I, 208 in group II, and 2501 in group III. Random samples were drawn from these groups after completion of the questionnaires and proving eligibility, so that a total of 70 individuals (grinding n = 20, packaging n = 24, control n = 26) were included in the study. The participants were predominantly men (67% (47/70)) and right-handed individuals (83% (55/70)). Only a few had a secondary occupation (9.0% (6/70)), and 61% (43/70) reported having sporting or physical hobbies. The three groups had comparable demographic data with regard to age (42.1 (±12.2) years), body mass index (BMI) (26.2 (±5.0) kg/m2), full employment level (91% (64/70)), and years of service at the company (16.1 (9 to 28) years). For flowcharts and detailed demographic data of the individual groups, please refer to our previous publication [17]. 3.2. Clinical Endpoints The DASH score, clinical parameters, and the Purdue Pegboard (PPB) Test score are shown in Table 2. Our mean scores are in good agreement with the normative DASH score [32]. Three DASH questionnaires were excluded from the analysis because of incompleteness. We did not expect any relevant differences between the grip strength of the right and left hands; therefore, we used the parameter dominant/non-dominant hand for further analysis. When comparing range of motion in three levels and grip strength with reference values from a healthy population, subdivided according to sex and age group, normal or below-average values were found [33–35]. This was also the case with the PPB test [36].
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