CHAPTER 2: LITERATURE REVIEW
3.11 COLLATION OF DATA
95 1000 ml of water, needed to drink 500ml plus 1000 ml ie 1500 ml over 2 hours ie 750 ml per hour to prevent dehydration.
As it was not possible to determine the fluid intake accurately during the shift, the fluid requirements could not be determined except for those who had reported that they had not taken any fluid or food across the shift. Their fluid requirements were calculated by converting their weight change across the shift directly into volume (1 gram being equivalent to 1 millilitre) and then dividing the amount by the number of hours they had worked.
96 compare within group changes over time, between group factors, and interactions between time and factors.
Categorical variables were described using frequency and relative frequency tables.
Comparisons of categorical dependant variables between groups was achieved using the McNemar’s chi square tests for paired groups, Bonferroni multiple comparison tests and Wilk’s Lamba.
97 Table 11: Statistical analysis used for each study objective and variable
Study objective Variable Statistical analysis
1.1.1 To determine the amount of fluid supplied by the contractors and the forestry workers.
Amount of fluid Descriptive statistics.
1.1.2 To determine the type of fluid supplied by the contractors and the forestry workers.
Type of fluid Descriptive statistics.
1.1.3 To establish and compare the prevalence and degree of dehydration occurring in forestry workers using USG and to determine whether there were high risk categories according to gender and job category.
USG Gender Job category
Descriptive statistics for USG readings pre shift, pre break and end shift.
Paired sample t-test to compare change in USG readings pre shift to pre break and pre break to end break and pre shift to end shift.
McNemar Chi square for the change in the classification of dehydration measured using USG between pre shift and end shift and between break and end shift.
Repeated measures of ANOVA to assess quantitative USG changes over two time points ie pre shift to pre break and pre break to end shift.
Wilk’s Lamba to assess the influence of job category and gender on USG readings over time.
98 Table 11: Statistical analysis used for each study objective and variable continued
Study objective Variable Statistical analysis
1.1.4 To determine whether the forestry workers
experienced symptoms of dehydration at the end of the shift.
Symptoms USG
Descriptive statistics.
Paired t-test to determine whether symptoms were related to USG readings.
Independent t-test to determine whether symptoms were related to gender.
1.1.5 To determine the forestry workers’ fluid requirements.
Body weight Descriptive statistics.
99 3.12 PERMISSION TO CONDUCT STUDY AND ETHICS APPROVAL
Ethical approval was obtained from the Nelson Mandela School of Medicine (Protocol E045/05) (Appendix L).
To comply with the ethics requirements, a week before the study commenced on each site, forestry supervisors, who were known and respected by the workers, went to talk to those who were harvesting in the areas to be included in the study. They explained the purpose of the study in the workers’ home language, what would be expected of them if they agreed to participate and when the study was taking place. In addition, the workers were handed out information sheets written in their home language (Appendix M).
On the first day of the study, the same forestry supervisors were present to remind the workers about the study and to answer any additional questions and to emphasize the fact that participation was voluntary. Those who were willing to participate had the informed consent read to them in their own language before being asked to either sign or thumbprint it.
100 3.13 SUMMARY
The study aimed to investigate the prevalence and degree of dehydration experienced by forestry workers harvesting trees during autumn and winter in SA. The samples were selected on the basis of convenience and included 79 workers in Richmond (winter) and 103 workers in Nelspruit (autumn). The participants were black African males and females who were employed as chainsaw operators or chainsaw operator assistants or rough liners or debarkers or stackers. The research teams comprised of dieticians and/or translators and/or CHW’s. After the Richmond research team’s initial training, a pilot study was conducted to ensure that the team was competent to collect data accurately and that the work flow was appropriate. No problems were experienced with the pilot study.
The data was collected over a period of 4 consecutive days, beginning on the Monday at each study site. The workers signed the informed consent if willing to participate after having the study explained to them in their own language. The prevalence and degree of dehydration was measured using USG readings as well as percent loss of body weight (Sawka et al 2007). A questionnaire was used to obtain sociodemographic data, medical data and whether the worker experienced symptoms of dehydration at the end of the shift.
Fluid brought by the workers was weighed using food digital scales. The type of fluid consumed was recorded. Data was entered into SPSS version 11.5 within 2 weeks of completion of the study. The data was entered twice to ensure accuracy. A 2 sided p value of <0.05 was considered as statistically significant. Groups were compared using sample t-tests, ANOVA and repeated measures of ANOVA for quantitative variables and
101 the McNemar’s Chi Square tests, Bonferroni multiple comparison tests and Wilk’s Lamba for categorical variables.
102 CHAPTER 4: RESULTS