OBJECTIVES: We conducted a systematic review of the health effects of hand-transmitted vibration exposure in tropical countries to determine the characteristics of hand-arm vibration syndrome in a warm environment and compared the findings with the results of the systematic reviews published by the US NIOSH.
METHODS: We searched major medical databases including MEDLINE, PubMed, Embase, CINAHL, Ovid and Cochrane based on the terms "hand arm vibration syndrome," "hand transmitted vibration," "vibration white finger" and "Raynaud" up to January 2011. Only studies conducted in a tropical or subtropical environment were selected for the review. The quality of the selected papers was assessed independently by two investigators using predefined criteria. A standard set of information was abstracted from the papers for review.
RESULTS: Only six papers from tropical countries and three papers from subtropical countries were available in the literature. No vibration white finger was reported in the tropical countries. Neurological symptoms were prevalent in the vibration-exposed workers. Finger coldness seems to be an important surrogate for vascular disorder in a tropical environment. Meta-analysis could not be performed due to inadequacy of the information reported in these papers.
CONCLUSIONS: The current dose-response relationship in ISO5349-1 for hand-transmitted vibration exposure is not applicable to a tropical environment. Further studies on hand-arm vibration syndromes in tropical countries are needed.
DESIGN: A cross-sectional study.
SETTING: 11 manufacturing factories in Malaysia.
PARTICIPANTS: 177 night-shift workers aged 40-65 years old were compared with 317 non-night-shift workers.
PRIMARY AND SECONDARY OUTCOMES: Participants completed a self-administered questionnaire on socio-demographics and lifestyle factors, 12-item Short Form Health Survey V.2 (SF-12v2) and the Pittsburgh Sleep Quality Index (PSQI). The Baron and Kenny's method, Sobel test and multiple mediation model with bootstrapping were applied to determine whether PSQI score or its components mediated the association between night-shift work and HRQoL.
RESULTS: Night-shift work was associated with sleep impairment and HRQoL. Night-shift workers had significantly lower mean scores in all the eight SF-12 domains (p<0.001). Compared with non-night-shift workers, night-shift workers were significantly more likely to report poorer sleep quality, longer sleep latency, shorter sleep duration, sleep disturbances and daytime dysfunction (p<0.001). Mediation analyses showed that PSQI global score mediated the association between night-shift work and HRQoL. 'Subjective sleep quality' (indirect effect=-0.24, SE=0.14 and bias corrected (BC) 95% CI -0.58 to -0.01) and 'sleep disturbances' (indirect effect=-0.79, SE=0.22 and BC 95% CI -1.30 to -0.42) were mediators for the association between night-shift work and physical well-being, whereas 'sleep latency' (indirect effect=-0.51, SE=0.21 and BC 95% CI -1.02 to -0.16) and 'daytime dysfunction' (indirect effect=-1.11, SE=0.32 and BC 95% CI -1.86 to -0.58) were mediators with respect to mental well-being.
CONCLUSION: Sleep quality partially explains the association between night-shift work and poorer HRQoL. Organisations should treat the sleep quality of night-shift workers as a top priority area for action to improve their employees' overall wellbeing.
METHODS: A cross-sectional study was conducted among Malaysian manufacturing workers, aged 40-65 years old. They completed a self-administered questionnaire on sociodemographics, lifestyle and family history, and the Pittsburgh Sleep Quality Index (PSQI) questionnaire. Waist circumference, blood pressure, fasting blood sugar, triglycerides and high-density lipoprotein levels were measured. Baron and Kenny's method, Sobel test and multiple mediation models with bootstrapping were used to determine whether the PSQI global score or its components mediated the association between night-shift work and MetS.
RESULTS: Of the 494 participants, 177 (36%) worked night shift and 51% were men. The prevalence of MetS was 37%. Night-shift work was independently associated with a twofold increase in the risk of MetS (adjusted OR: 1.92, 95% CI 1.24 to 2.97). However, the association between night-shift work and MetS did not appear to be modified by sex. Night-shift workers also reported significantly poorer sleep quality, longer sleep latency, shorter sleep duration, sleep disturbances and daytime dysfunction. Robust mediation analysis nonetheless showed that neither PSQI global score nor its components mediated the association between night-shift work and MetS.
CONCLUSION: Early screening and management of MetS and the development of programmes to improve sleep quality should be carried out among night-shift workers. Future research should investigate other modifiable mediators linking night-shift work and MetS.
METHODS: We conducted a series medical examinations among the forestry, construction and automobile industry workers in Malaysia adopting the compulsory medical examination procedure used by Wakayama Medical University for Japanese vibratory tools workers. We matched the duration of vibration exposure and compared our results against the Japanese workers. We also compared the results of the Malaysian tree fellers against a group of symptomatic Japanese tree fellers diagnosed with HAVS.
RESULTS: Malaysian subjects reported a similar prevalence of finger tingling, numbness and dullness (Malaysian=25.0%, Japanese=21.5%, p=0.444) but had a lower finger skin temperature (FST) and higher vibrotactile perception threshold (VPT) values as compared with the Japanese workers. No white finger was reported in Malaysian subjects. The FST and VPT of the Malaysian tree fellers were at least as bad as the Japanese tree fellers despite a shorter duration (mean difference=20.12 years, 95%CI=14.50, 25.40) of vibration exposure.
CONCLUSIONS: Although the vascular disorder does not manifest clinically in the tropical environment, the severity of HAVS can be as bad as in the temperate environment with predominantly neurological disorder. Hence, it is essential to formulate national legislation for the control of the occupational vibration exposure.