Socio-demographic, lifestyle and health characteristics among snus users and dual tobacco users in Stockholm County, Sweden

In all, 57,000 individuals aged 18-84 years were randomly selected from the background population of Stockholm County after stratification for residential municipality. Stockholm County has approximately 1.9 million inhabitants, corresponding to 21% of the Swedish population. Administrative records held by Statistics Sweden, including name, address and date of birth of all Swedish residents, were used to identify the study population [23]. Among invited individuals, 34,707 (61% of all eligible) participated in the survey. Compared with Stockholm county census data, non-respondents included a higher proportion of men, subjects under the age of 45, foreign-born, single or separated, unemployed and in the lowest quartile of income.

Subjects were sent a study invitation via traditional mail, and asked to complete a comprehensive questionnaire, choosing between paper and web-based forms. The latter was available at an URL provided in the letter together with a personal login. Of the respondents, 86.4% chose paper and 13.6% web-based questionnaires. Paper and web-based questionnaires contained identical questions eliciting information on socio-demographic factors, health parameters, physical activity, alcohol consumption, anthropometry and other life circumstances. The majority of items were validated instruments often used for health surveys, in Sweden and elsewhere.

Current smoking and snus use was assessed using the following question: "Do you [currently smoke; use snus] daily?". Current tobacco use was categorized into four mutually exclusive groups - no daily use (including former use), exclusive daily use of snus, exclusive daily smoking or daily dual use (both smoking and snus use). Occasional tobacco use was not elicited in the survey and therefore not taken into account in this study.

Age and current profession were reported by the participants while levels of education and income, measured as individualised disposable income calculated from the total family income, were taken from the LISA register maintained by Statistic Sweden [24]. Age was categorized into 10-years intervals. The allocation of occupational class was based on the Swedish Socioeconomic Classification which provides a measure of class based on occupation [25, 26]. It classifies individuals in the labour force into self-employed and employed. The latter group is sub-grouped according to the average educational level required for any particular occupation, yielding five occupational categories: unskilled manual worker, skilled manual worker, low-level clerk, intermediate level clerk, high level clerk. Education was grouped in three categories (high: university studies; intermediate: secondary school; low: only compulsory education + vocational training), and income was categorised in quintiles.

Participants were also asked to report their weight and height, their alcohol consumption during an average week (from which a summary variable expressing average consumption in gr of ethanol/week was derived) and their frequency of binge drinking (defined as the equivalent to two bottles of wine during the same occasion). Consumption of fruit and vegetables was assessed by the questions "How often do you eat [fruit or berries; a portion of vegetables or root vegetables]?" Information on physical activity was obtained by asking "How many days per week do you exercise for at least 30 minutes intensely enough to start sweating"? Body Mass Index (BMI) was calculated as the ratio between weight in kg and the square of height in meters (kg/m²), and categorised as underweight; normal weight; overweight or obese (corresponding to BMI < 18.0; 18.0-24.9; 25.0-29.9; and ≥ 30). Average alcohol consumption during one week was dichotomized as risky alcohol consumption (men: > = 170 gr pure alcohol/week, equivalent to 14 standard drinks; women: > = 110 gr/week, equivalent to 9 standard drinks) versus not risky, based on the recommendation from the Swedish Council for Information on Alcohol and Other Drugs (CAN). Consumption above the cut-off point is considered to increase the risk of health damages [27]. Three mutually exclusive categories were employed for frequency of binge drinking (less than monthly or never; monthly, but not weekly; weekly). Fruit and vegetable consumption were categorised as once a week or less; several times a week to daily; several times a day. Days per week with at least 30 minutes of intense physical activity were collapsed into three categories (< 2; 2-4; 5+ days/week).

Perceived health was self-reported on a 5-points Likert scale, collapsed into three categories: very poor/poor; fair; very good/good. Lastly, psychological distress was assessed via the twelve-item version of the General Health Questionnaire (GHQ-12). GHQ-12 is a well-validated self-report screening tool that is internationally used to identify general, non-psychotic and context-free mental and affective ill being, so called common mental disorders [28]. The GHQ-12 is also predictive of more severe mental disorders [29]. The score of GHQ-12 ranges from 0 to 12 and the recommended cut-off point of three or more symptoms was employed to define psychological distress [28].

Prevalence odds ratios (ORs) of current daily tobacco use versus no current use were used as measure of cross-sectional associations with selected socio-demographic, lifestyle and health characteristics, based on logistic regression models, using SAS 9.1. In addition, ORs of snus use and dual use versus smoking were calculated with regard to lifestyle and health characteristics. Adjustments were made for age (grouped as 18-44, 45-64, ≥ 65 years) and occupational class, where applicable. Analyses of current daily exclusive snus use or smoking versus no current daily tobacco use were further adjusted for past use of the other type of tobacco. In addition, BMI and physical activity were mutually adjusted, as were education, income and occupational class. All analyses were done separately for men and women.

To our knowledge, this is the first study presenting a comprehensive description of health related characteristics of snus users in Sweden. The large size of the sample allowed us to include women in the analysis, while most other studies were restricted to men. Other strengths include the wide range of available information on social and health related characteristics.

Non-participation in this survey (about 39% of the original sample) may have lead to selection bias. Because tobacco users are less likely than non-users to participate in surveys the actual prevalence of tobacco use in this population sample may be underestimated [46]. Likewise, the association of tobacco use with health characteristics may be over- or underestimated if non-participation was also correlated with poor health or social disadvantage. However, it is unlikely that this would happen differentially according of the type of tobacco used. Further, all behavioural characteristics including tobacco use may be affected by misclassification due to imperfect recall or infidelity of self-reports, but again this is unlikely to have occurred differentially for snus users compared to smokers. The generalisability of our results to other populations is limited due to product-specific characteristics and the trends of use of Swedish snus compared to smokeless tobacco used in other parts of the world, e.g. in USA, India or other Eastern countries [6, 47]. However, the general conclusion of our study, i.e. that there is a need of a careful analysis of socio-demographic as well as lifestyle and health-related characteristics of smokeless tobacco users, is certainly applicable to other contexts, especially when new consumers are likely to emerge in response to a changing market.