ORIGINAL ARTICLE Betel nut chewing and other risk factors ...

International Journal of Obesity (2006) 30, 359–363 & 2006 Nature Publishing Group All rights reserved 0307-0565/06 $30.00 www.nature.com/ijo

ORIGINAL ARTICLE Betel nut chewing and other risk factors associated with obesity among Taiwanese male adults W-C Chang1, C-F Hsiao2, H-Y Chang 3, T-Y Lan1, C-A Hsiung2, Y-T Shih3 and T-Y Tai1 1

Division of Gerontology Research, National Health Research Institutes, Taipei City, Taiwan; 2Division of Biostatistics and Bioinformatics Research, National Health Research Institutes, Taipei City, Taiwan and 3Division of Health Policy Research, National Health Research Institutes, Taipei City, Taiwan Objective: The research aimed at examining betel nut chewing and other risk factors associated with obesity among Taiwanese male adults. Design: The research analyzed the data obtained by the 2001 National Health Interview Survey in Taiwan that covered all the administrative divisions in Taiwan. Multistage stratified systematic sampling design was adopted for survey. All members of a sampled household received the interview. Subjects: The research analyzed questionnaires answered by nonaboriginal male respondents aged between 20 and 59 years old, and the total number of samples analyzed read 6126. Since very few female subjects chewed betel nut, they were excluded from the analysis. Measurements: Criteria of obesity was defined as body mass indexX27 kg/m2. The variables incorporated for analysis included the respondents’ status of betel nut chewing, age, educational background, presence of hypertension and diabetes mellitus, drinking and smoking status, exercise status, and demand for physical strength at job. Generalized estimating equations model was employed to estimate the odd ratios (with 95% CI) of obesity of each independent variable. Results: Approximately 16.2% of respondents were obese. The distribution of betel nut chewing was current chewers 15.9%, ex-chewers 4.3%, and nonchewers 79.8%. After controlling above-mentioned independent variables, hypertension, diabetes mellitus, betel nut chewing, never exercising, and sedentary jobs were closely associated with obesity. Conclusion: The research found that betel nut chewing closely associated with obesity. The increased appetite of betel nut chewers is speculated as the underlying cause. The prospective study is needed to clarify this issue. In addition to increasing the risk of developing oral cancer, betel nut chewing seemed to be related with another health hazard: obesity. International Journal of Obesity (2006) 30, 359–363. doi:10.1038/sj.ijo.0803053; published online 23 August 2005 Keywords: betel nut; BMI; Taiwan; male

Introduction According to the latest statistics published by the Directorate General of Budget, Accounting and Statistics, Executive Yuan, Taiwan has marched into a developed country with an average GNP of US$13 995. Together with the economic growth, the prevalence of obesity among Taiwanese adults has also exceeded 10%.1 The purpose of this study was to explore the risk factors associated with obesity in Taiwan. In addition to various commonly reported risk factors, betel nut chewing was also included. Correspondence: Dr T-Y Tai, Division of Gerontology Research, National Health Research Institutes, Room 4110, 4F, No. 161, Sec. 6, Mincyuan E. Rd, Neihu District, Taipei City 114, Taiwan. E-mail: [email protected] Received 24 March 2005; revised 10 June 2005; accepted 5 July 2005; published online 23 August 2005

Betel nut chewing, a special habit popular among residents in South and Southeast Asia,2,3 is generally believed to be a risk factor of developing oral cancer.2,4–7 Betel nut contains unique alkaloid, and its major constituents – arecoline and arecaidine – are capable of inhibiting g-aminobutyric acid (GABA) receptor.8 The previous researches suggest that betel nut chewing can increase body mass index (BMI)9 or contribute to central obesity.10 Obesity is an important risk factor for a legion of chronic diseases, such as diabetes mellitus, cardiovascular diseases, and hypertension.11–17 However, the number of researches studying the relationship between betel nut chewing and body size remains fairly limited. As Taiwan is marked by a high prevalence rate of betel nut chewing18 and has witnessed an increasing incidence of the above-mentioned chronic diseases, our research has accordingly examined the relationship between betel nut chewing and body build.

Betel nut chewing and obesity in Taiwan W-C Chang et al

360

Materials and methods Subjects Data consulted by our research mainly came from the 2001 National Health Interview Survey in Taiwan, sampling from all the administrative divisions in Taiwan. The crosssectional data used household as its smallest sampling unit, and all the members of a sampled household received the interview. The response rate was more than 85%.19 The questionnaires answered by nonaboriginal male respondents aged 20–59 years read 6423. Among them 297 respondents were excluded because of incompleteness of data. Total number of samples analyzed was 6126. Since aborigines occupy less than 2% of the total population and very few nonaboriginal female subjects have betel nut chewing experience (0.2% for ex-chewers and 3.1% for current chewers), they were not included in the analysis.

Dependent variable The World Health Organization defines obesity as BMIX30 kg/m2. This Caucasian standard corresponds approximately to X27 kg/m2 for Taiwanese adults.1,20 Obesity, as the dependent variable of the research, was accordingly defined by the criterion of BMIX27 kg/m2.

Experience of betel nut chewing The major independent variable of the research was the experience of betel nut chewing, and according to which the subjects were divided into three groups: nonchewers, ex-chewers, and current chewers. The nonchewers (including only once or twice experience) were defined as the reference group.

Other independent variables Other independent variables included the respondents’ age, educational background, presence of hypertension and diabetes mellitus, drinking and smoking status, exercise status, and demand for physical strength at job. Age and educational background were treated as continuous variables. Educational background referred to the number of years receiving primary and above education. The presence of hypertension was defined as those receiving antihypertensive agents based on the 2000–2001 National Health Insurance outpatient and in-patient records; respondents with no hypertension (blood pressure o140/90 mmHg) formed the reference group. The presence of diabetes mellitus was defined as those receiving hypoglycemic agents based on National Health Insurance records; reference group comprised respondents with no diabetes mellitus. Respondents were divided into various groups as follow: four groups of alcohol drinking status: nondrinkers (the reference group), those drinking alcohol less than once a month, those drinking alcohol once to thrice a month, and those International Journal of Obesity

drinking alcohol once a week or more often; four groups of smoking status: nonsmokers (the reference group), exsmokers, occasional smokers, and regular smokers; and three groups of exercise status: nonexercisers (the reference group), occasional exercisers, and regular exercisers. Regular exercisers referred to those exercising at least six times every 2-weeks, and more than 30 min each time. Demand for physical strength at job was divided into three different levels in accordance with the respondents’ occupations: sedentary, intermediate, and laborious. Sedentary jobs included physicians, lawyers and other highly professional workers, general office workers, retired persons and people between jobs, etc. Intermediate physical strength at jobs incorporated construction and engineering site supervisors, bakers, carpenters, peddlers, technicians, street cleaners, nannies, janitors, waiters or waitresses, students, etc. Laborious jobs included: construction workers, nonclerical career soldiers, farmers, fisherpersons, miners, seafarers, etc.

Statistical analysis Since individual respondents might come from the same household, the data are similar in nature and thus there might be a lack of independence among observations. As an alternative approach, the generalized estimating equations (GEE) model, which resembles the general logistic regression model, but takes into account the dependence among observations, was adopted to perform multiple logistic regression analysis and to estimate the odds ratio (with 95% CI) of obesity of each independent variable.

Results The average age was 37.5710.8 years (mean7s.d.), the mean value of BMI was 23.873.4 kg/m2, and the mean educational years was 11.673.3 years. Breakdown of respondents by the status of betel nut chewing read 15.9% (current chewers, whose average length of betel nut chewing was13.4 years), 4.3% (ex-chewers, the average length of chewing 11.3 years), and 79.8% (nonchewers) (Table 1). As Table 2 indicates, after controlling for the other independent variables, hypertension, diabetes mellitus, betel nut chewing, exercising, and sedentary job were closely associated with obesity. Respondents who have the habit of betel nut chewing were more likely to be obese than those who never chewed (odds ratio 1.475, Po0.001). Also those who were ex-betel nut chewers tended to be more obese than those who never chewed (P ¼ 0.052). The relationship between betel nut chewing and the respondents’ daily consumption of rice or noodles (not incorporated into the regression model for control) was further examined by w2-test. Results revealed that 39.8% of current betel nut chewers took three or more helpings of rice (noodles) per day. The percentage dropped to 36.4% for ex-chewers and decreased further to 32.1% for


361 Characteristics of the study subjects

Variables

Mean age7s.d. (year) Mean educational level7s.d. (year) Mean BMI7s.d.

Table 2

Obese (n ¼ 992)

Nonobese (n ¼ 5134)

Total (n ¼ 6126)

39.34710.1 11.2673.3

37.17710.9 11.6873.3

37.53710.8 11.6173.3

29.3472.3

22.7672.4

23.8273.4

BMI group (%) BMI X27 24pBMI o27 BMI o24

100.0 0.0 0.0

0.0 33.4 66.6

16.2 28.0 55.8

Hypertension (%) No Yes

85.2 14.8

95.0 5.0

93.4 6.6

Diabetes mellitus (%) No Yes

92.7 7.3

97.0 3.0

96.3 3.7

Alcohol drinking Never Less than once per month Once–thrice per month More than once per week

50.7 11.1 11.7 26.5

54.4 10.9 12.7 22.0

53.8 11.0 12.5 22.7

Smoking status Never Ex-smokers Occasional smokers Regular smokers

42.3 7.1 3.7 46.9

46.0 4.5 3.4 46.2

45.4 4.9 3.4 46.3

Betel nut chewing Never Ex-chewers Current chewers Exercise status Never Occasional Regular

73.9 5.7 20.4

81.0 4.0 15.0

79.8 4.3 15.9

54.9 24.6 20.5

51.0 27.3 21.6

51.7 26.9 21.4

Demand for physical strength at job Sedentary 64.9 Intermediate 25.7 Laborious 9.4

59.0 28.6 12.5

59.9 28.1 12.0

nonchewers. The percentage of eating less than two helpings of rice (noodles) was 25.2% for current chewers, 29.6% for ex-chewers, and 31.8% for nonchewers. It is obvious that the daily consumption of rice (noodles) for betel nut chewers was greater than that for nonbetel nut chewers (Po0.001, w2-test) (Figure 1). However, the association of rice (noodles) consumption and obesity was not proved by w2-test.

Results of multivariate analysis on factors associated with obesitya Odds ratio (95%CI)

Age Education background

1.004 (0.997–1.012) 0.988 (0.963–1.013)

Hypertension No (ref.)b Yes

2.757 (2.169–3.505)z

Diabetes mellitus No (ref.) Yes

1.642(1.184–2.275)w

Alcohol drinking Never (ref.) Less than once per month Once-thrice per month More than once per week

1.108 (0.882–1.393) 0.976 (0.779–1.222) 1.164 (0.963–1.407)

Smoking status Never (ref.) Ex-smokers Occasional smokers Regular smokers

1.314 (0.957–1.804) 1.094 (0.753–1.588) 0.887 (0.745–1.055)

Betel nut chewing Never (ref.) Ex-chewers Current chewers

1.384 (0.997–1.921) 1.475 (1.200–1.814)z

Exercise status Never (ref.) Occasional Regular

0.879 (0.739–1.046) 0.822 (0.680–0.995)*

Demand for physical strength at job Sedentary (ref.) Intermediate Laborious

0.864 (0.731–1.021) 0.685 (0.537–0.875)w

a

GEE models of risk factors associated with obesity. bRef. : reference group. *Po0.05 wPo0.01 zPo0.001.

45.0%

3

40.0% 35.0% Percentage

Table 1

30.0% 25.0% 20.0% 15.0% 10.0% 5.0% 0.0%

Non-chewers

Ex-chewers

Current-chewers

Figure 1 Relationship between betel nut chewing and daily consumption of rice (noodles). Current chewers ate significantly more rice (or noodles) per day than nonchewers with Po0.001 by w2 test.

Discussions Obesity is a common chronic disease in Taiwan1 and worldwide.15,21,22 Our analysis confirmed that betel nut

chewing was associated with obesity. This result echoed the finding of a research conducted on the people of Bangladeshi ancestry in east London.10 International Journal of Obesity


362 To clarify if there is any significant difference between the 297 samples excluded from our analysis because of their data incompleteness (incomplete samples) and the 6126 analyzed samples with complete data (complete samples), the comparison of the two sub-samples was executed. It was found that the incomplete samples were older, had a lower education level, higher prevalence of betel nut chewing, lower regular exercising rate, and a higher rate of laborious jobs than the complete samples. We analyzed two additional models, in which both complete and incomplete samples were included, to adjust the potential bias resulted from the difference between these two subsamples. In the first model, we assumed conservatively all the 297 incomplete samples were nonobese, and in model 2 we assumed radically that they were all obese. Both models showed similar results and confirmed the finding of our original model (only included the complete samples) that betel nut chewing was significantly associated with obesity (data not shown). The contribution of betel nut chewing to obesity may lie in the fact that the alkaloid in betel nut can promote one’s appetite by inhibiting GABA receptor.23 Although our analysis showed that betel nut chewers took more staple food than nonchewers did, we did not have data about the intake of calories. The assumption that the obesity of betel nut chewers is related with increased food intake needs further investigation. In accordance with other reports, our study also found that the presence of hypertension,24–26 diabetes mellitus,12,14,17,27,28 lack of exercise,29,30 and those with sedentary jobs31 were associated with obesity (Table 2). Respondents who did regular exercise or laborious jobs had significantly lower percentage of being obese, suggesting that more physical activities do help reduce obesity. In conclusion, betel nut chewing, the presence of hypertension and diabetes mellitus, and sedentary lifestyle are closely associated with obesity. Since obesity might lead to the development of diabetes and hypertension, the association between betel nut chewing and diabetes mellitus, and between betel nut chewing and hypertension is currently under investigation.

Acknowledgements We thank all the task force members at the Bureau of Health Promotion of DOH, and National Health Research Institutes for their generous assistance in providing the National Health Insurance data and the results of the 2001 National Health Interview Survey in Taiwan.

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