Association between sleeping hours, working hours and obesity in Hong Kong Chinese: the 'better health for better Hong Kong' health promotion campaign.

OBJECTIVE: To study the inter-relationships between sleeping hours, working hours and obesity in subjects from a working population. RESEARCH
DESIGN: A cross-sectional observation study under the 'Better Health for Better Hong Kong' Campaign, which is a territory-wide health awareness and promotion program.
SUBJECTS: 4793 subjects (2353 (49.1%) men and 2440 (50.9%) women). Their mean age (+/-s.d.) was 42.4+/-8.9 years (range 17-83 years, median 43.0 years). Subjects were randomly selected using computer-generated codes in accordance to the distribution of occupational groups in Hong Kong.
RESULTS: The mean daily sleeping time was 7.06+/-1.03 h (women vs men: 7.14+/-1.08 h vs 6.98+/-0.96 h, P<0.001). Increasing body mass index (BMI) was associated with reducing number of sleeping hours and increasing number of working hours reaching significance in the whole group as well as among male subjects. Those with short sleeping hour (6 h or less) and long working hours (>9 h) had the highest BMI and waist in both men and women. Based on multiple regression analysis with age, smoking, alcohol drinking, systolic and diastolic blood pressure, mean daily sleeping hours and working hours as independent variables, BMI was independently associated with age, systolic and diastolic blood pressure in women, whereas waist was associated with age, smoking and blood pressure. In men, blood pressure, sleeping hours and working hours were independently associated with BMI, whereas waist was independently associated with age, smoking, blood pressure, sleeping hours and working hours in men.
CONCLUSION: Obesity is associated with reduced sleeping hours and long working hours in men among Hong Kong Chinese working population. Further studies are needed to investigate the underlying mechanisms of this relationship and its potential implication on prevention and management of obesity.