In this study of a representative population of adult Singaporeans and Singapore permanent residents, we found that 12.6% of all adult Singapore residents reported heavy drinking in the past 12 months, and 15.9% reported lifetime heavy-drinking. There were strong socio-demographic differences between heavy-drinkers and non-drinkers, with heavy-drinkers being more likely to be men, younger, single, and earning higher income. Malays were much less likely to be heavy drinkers compared to the Chinese. Heavy drinking was positively associated with major depression, the presence of any mood disorder, and chronic pain. It was also strongly associated with alcohol dependence and alcohol abuse, and nicotine dependence. Overall, heavy drinkers reported lower quality of life compared to non- heavy drinkers on the EuroQoL indexed score and Visual Analogue Scale.
Data from the National Health Survey in 2004 previously suggested a binge-drinking prevalence of about 10% [13]. Our results of 12.6% for heavy drinking are consistent with the data obtained from 2004. Additionally, both studies identified the young, males, and people with higher incomes as being more likely to drink heavily, while Malays were less likely to do so [13]. The strong ethnic differences in heavy-drinking rates are likely to be due to the role of culture and religion as a protective factor. Malays in Singapore are almost all Muslims, for whom there is a religious prohibition on alcohol consumption. Further analyses of our data show that the proportion of heavy drinkers (both over twelve months or lifetime) in Malays who drink was similar to or higher than the proportion in Chinese who drink (not shown in tables), in contrast to the overall prevalence of heavy drinking, which is much lower among Malays. This suggests that the effect of ethnicity on heavy drinking works via reducing initiation of drinking rather than drinking volume. This is consistent with the hypothesis that the protective effect of ethnicity on heavy drinking is mediated through religion, since Islam prohibits alcohol consumption. We also note a very high prevalence of alcohol consumption among people of “Others” ethnicities, with an odds of heavy drinking of about 7 times higher than the Chinese. This increase is statistically significant. In Singapore, the majority of people classified as “Others” are people of Eurasian or Caucasian origins, although other ethnicities such as Thai, or Japanese are also classified in this group. Further research is needed to evaluate which ethnicities within this group are drinking more, and to understand the context of the heavy alcohol consumption, so that appropriate intervention programmes can be designed and implemented.
The prevalence of heavy drinking is much lower than those reported in non-Asian countries [9, 10]. Heavy drinking in Singapore is primarily a condition of the young, as has been reported in other studies [9, 10]. Our findings with regard to income and marital status are consistent with findings reported previously [9, 10, 19]. We did not detect an inverse association with education, which has been reported elsewhere [19].
Alcohol use in Singapore in the past was much lower compared to Western and some Asian countries, with low rates seen particularly amongst Malays and women [13]. However, both published studies and anecdotal evidence suggest that alcohol use is becoming accepted as a social norm in Singapore [13]. Alcohol use disorder has increased in recent years, especially among the young [12]. Alcohol use and abuse control policies in Singapore depend on a variety of measures, including heavy taxation on alcohol products [20], legislation such as restrictions on sale of alcohol to minors and anti-drink-driving laws, and promotional campaigns to curb misuse of alcohol by the Health Promotion Board and the Traffic Police [21].
We found an association of heavy drinking with mental illnesses, in particular major depression, also consistent with findings from other studies [2, 22, 23]. The strong association with alcohol abuse and use is not unexpected. However, the vast majority of heavy drinkers do not have alcohol use disorders, and alcohol use disorders do not adequately predict heavy drinking. The association of heavy drinking with depression, and to a lesser extent, with anxiety disorders, is consistent with the higher prevalence of unhealthy lifestyle behaviour (including poorer diet, lower levels of physical activity, higher smoking prevalence) that has been reported among people with psychiatric disorders [24, 25]. Heavy drinking was also positively and strongly associated with nicotine dependence, again consistent with results from other studies [26]. In our data, more than a quarter of people who fulfilled criteria for major depressive disorder reported heavy drinking in the last 12 months. This suggests that doctors managing patients with depression may need to assess for and manage unsafe alcohol use in their patients even in the absence of alcohol abuse or alcohol dependence. There is some evidence that reducing alcohol consumption might improve depressive symptoms [2].
We note a significant positive association between chronic pain and lifetime heavy drinking, and a borderline significant finding with twelve-month heavy drinking. Further, heavy drinkers with or without alcohol use disorder reported poorer scores on the pain/discomfort dimension on the EuroQoL 5D compared to non-heavy drinkers. A possible explanation for this association is that this relationship could be mediated through mental disorders such as major depression: we observe a positive association between heavy drinking and depression in this paper, and previous analyses of our dataset have shown that the prevalence of mental disorders including depression is higher among those with chronic pain [27]. Another explanation for these associations may be that the higher prevalence reflects attempts by persons living with depression or chronic pain to alleviate their symptoms through the use of alcohol.
Our results show that the greatest declines to quality of life and to work-day loss relate to the presence of mental illnesses, and do not suggest that heavy drinking in the absence of alcohol use disorder is associated with significant loss of quality of life, nor with loss in work-days. Other studies have reported changes in quality of life associated with binge drinking [28, 29], and a recent study in Norway has suggested that binge drinking is associated with absenteeism in the workforce [30]. This discrepancy could be due to a ceiling effect in the instruments used [31], with a relative lack of discrimination among otherwise well individuals. We did detect differences in quality of life among younger participants who drank heavily, compared to those who did not, on the VAS but not using the index score. These results are consistent with findings from other countries (28,29), and suggest that for younger, otherwise healthy populations, the VAS may be more discriminatory than the index scores.
In the older age-groups, higher quality of life was unexpectedly reported among heavy drinkers without alcohol use disorder compared to non-heavy drinkers. This may reflect reverse causation where healthy individuals are more likely than persons with physical illnesses to continue drinking, or it may be that there is no decline in quality of life associated with heavy drinking for the majority of drinkers, who may find the social interaction associated with drinking a strong promoter of emotional well-being. Interestingly, a recent study in the US also reported that heavy drinkers had higher measures of positive health in some domains [32].
There are several limitations in our study. We used a cross-sectional design, and while our data give nationally representative figures, we were unable to establish the causality of associations that we have found. Our contact rate of 67.5% and response rate of 75.9% are reasonable and consistent with response rates obtained in population-based surveys conducted elsewhere. However, contact and response rates of heavy drinkers may differ from non-heavy drinkers, and this differential response rate may bias our prevalence estimates. A priori, we assume that heavy drinkers are likely to have lower contact and response rates. If so, our prevalence estimates would represent a lower limit, and the true prevalence may be higher than estimated.
We used an operational definition of heavy drinking as a consumption of 4 or 5 drinks (depending on gender) in a single day, in contrast to the traditional binge drinking definition of 4 or 5 units over a single drinking episode. Our results therefore does not measure 12-month binge drinking rates, and direct comparisons with binge drinking rates cited in other studies are not possible. Because binge drinkers are heavy drinkers, but heavy drinkers need not be binge drinkers, our prevalence estimate may be an overestimate of the 12-month binge drinking rate, and serve as an upper estimate of the true binge drinking rate. The definition for 12- month heavy drinking (largest number of drinks in a single day) was different from lifetime heavy drinking (usual number of drinks). The lifetime heavy drinking estimate will underestimate the true prevalence of lifetime binge drinking. We believe 12-month heavy drinking is a better proxy for binge drinking than the lifetime one.
Finally, we used face-to-face interviews for this study. Participants may not have reported accurate consumption rates because of their perceptions of the social acceptability of alcohol consumption. This may be so especially amongst females or Malays, where societal expectations are that they do not drink. Conversely, young males may have over-reported their consumption patterns. We have tried to reduce this misclassification bias by training our interviewers to administer the interviews in a sensitive and neutral manner, and using standard questionnaires.
