ORIGINAL ARTICLE

Increased plasma homocysteine levels in shift working bus drivers

P J F Martins¹, V D’Almeida¹, N Vergani², A B A Perez² and S Tufik¹

¹ Department of Psychobiology, Universidade Federal de São Paulo–Escola Paulista de Medicina, São Paulo, Brazil
² Department of Morphology, Universidade Federal de São Paulo–Escola Paulista de Medicina

Correspondence to:
Correspondence to:
Dr V D’Almeida, Rua Napoleão de Barros, 925, São Paulo, SP Brazil 04024-002;
valmeida.dped{at}epm.br

Background: Previous studies have indicated an association between shift work and cardiovascular disease. There is also considerable epidemiological evidence that hyperhomocysteinemia is an independent risk factor for cardiovascular disorders.

Aims: To analyse plasma homocysteine levels in shift work bus drivers, and to investigate possible relations with sleep parameters and other biochemical factors.

Methods: Blood samples were collected from 30 male shift working long-haul bus drivers in a Brazilian sample and analysed for plasma levels of homocysteine, folic acid, vitamin B₁₂, and serum lipids. A group of 22 daytime workers, matched for age and body mass index served as controls. The incidence of mutations in the gene coding for methylene tetrahydrofolate, an enzyme which is related to hyperhomocysteinemia, was also assessed. Polysomnographic recordings were obtained from the target group.

Results: Bus drivers showed significantly higher levels of plasma homocysteine than the control group (18.57 v 9.43 µM). Most of the other biochemical, behavioural, and molecular parameters did not differ between groups. Likewise, sleep parameters appeared to be within the normal range.

Conclusions: The significantly increased plasma homocysteine levels in long-haul bus drivers did not appear to be secondary to other biochemical or behavioural problems in this group. These results suggest that hyperhomocysteinemia may be involved in the increased incidence of cardiovascular diseases observed in shift workers.

Keywords: amino acid metabolism; atherosclerosis; circadian rhythms; coronary disease; stress

Abbreviations: AHI, apnoea/hypopnoea index; CVD, cardiovascular disease; Hcy, homocysteine; HDL, high density lipoprotein; LDL, low density lipoprotein; MTHFR, methylene tetrahydrofolate reductase; OR, odds ratio; REM, rapid eye movement; REML, REM sleep latency; SEff, sleep efficiency; SOL, sleep onset latency; SWS, slow wave sleep; TST, total sleep time; VLDL, very low density lipoprotein; WASO, wakefulness after sleep onset

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