Among subjects reporting an occupational exposure to each respective type of dust, the duration of occupation with leather dust exposure was significantly longer among cases than controls (P = 0.007), with a median exposure of 24 years among 37 cases versus 7 years among 26 controls (Fig. 1).
Results show that site size increases with the number of occupants and hence, the amount of in-patch foraging competition, while size sorting increases with the duration of occupation and hence, in-patch residence time.
Ownership, signalling importance and role of the mother, depended on the availability of the room and duration of occupation.
For a given occupation, the effect of risk factors (duration of occupation and age) on the incidence of MSDs among workers was established by applying multivariate logistic regression.
The concept is that with increasing duration of occupation, exposure to infection is more likely even if the job itself has a lower level of social contact.
A multiple logistic regression was conducted using presence of CANS as the categorical dependant variable (0 = No, 1 = Yes), using the independent variables identified as risk-factors in the binary logistic regression analysis of each region, while controlling for potential confounders such as age, gender and duration of occupation.
This study has several strengths, they are as follows: (1) it is one of the only two studies to investigate both paternal and maternal occupational contact level, which may involve less misclassification than using only paternal data; (2) it is the first study to take account of duration of occupation.
– To improve planning of our operational site by comparing the durations of intervention scheduled by the surgeons and the real durations of occupation of room of intervention, surgical procedure and surgical operation.
Interestingly, even when no weighting was assigned (multiplication factor 1.0 for both medium and high social contact occupation), there was still a significant interaction between rural/urban status and the duration of parental occupation on the risk of childhood leukaemia, which further support the importance of including duration as part of the parental occupational social contact measure.
In conclusion, our results indicated that including information of the duration of parental occupation may be important when studying the association between parental occupational social contact and childhood leukaemia.
