In the past, advances in technology have caused a decrease in the time spent on physical activities and an increase in the time spent on sedentary behaviors [
Although the research on sedentary behavior has been dominated by studies on its association with physical health, there is increasing research focusing on the association between sedentary behavior and mental health, especially depression [
Among the Dutch population, there is a 14% yearly prevalence of self-reported poor mental health (defined by the Mental Health Inventory, MHI-5 ≤ 60) [
Most studies on sedentary behaviors have focused on TV viewing. However, sedentary behaviors involve domains other than sitting during leisure, such as sitting at work or sitting during transport. Among working adults, who represent a major part of the adult population, a significant amount of time is spent at work, and the majority of their total sitting time each day is likely to be at work due to the organization of the work [
With respect to the observed associations between TV viewing and mental health, several explanations can be proposed. In addition to possible physiologic mechanisms, there are possible behavioral explanations; for example, extended time spent viewing TV may lead to social isolation which adversely affects mental well-being [
Due to the current lack of knowledge on the relationship between various sedentary behaviors and mental health, the aim of this study was to explore the association between domain-specific sitting with mental health among workers and nonworkers. Weight status has shown to be associated with sedentary behaviors [
Data were derived from the Doetinchem Cohort Study, a Dutch, prospective, population-based study among residents from a town (Doetinchem) in the Netherlands. The data collection began among persons aged 20–59 years from 1987 to 1991 as part of the Monitoring Project on Cardiovascular Disease Risk Factors [
The general aim of the Doetinchem Cohort Study is to study the impact of (changes in) lifestyle behaviors and biological risk factors on health outcomes during ageing [
Sedentary behavior was assessed by self-reported time spent sitting during a usual week over the past 12 months. The format of the sitting-time questions was similar to the questions about physical activity, which were designed for the European Investigation into Cancer and Nutrition (EPIC) [ traveling by motor vehicle (such as train, bus, car, tram, motorbike, motor) during commuting, work, leisure; sitting at work (behind desk, computer, or meeting); sitting during leisure time while reading and/or studying, TV viewing, sitting behind the computer, other sitting activities (talking with friends, playing games, listening to music, etc.).
From these items, three subscores were calculated by totaling the time spent sitting in each category: hours per week sitting during transport either for work or leisure time, hours per week sitting during work, and hours per week sitting during leisure time (either reading or studying, viewing television, computer time, or other sitting activities). Sitting time per domain was calculated only in those cases for which all underlying sitting activities were not missing. In all other cases, sitting time for the specific domain was considered as missing. Further, the time reported on each sitting activity was maximized at eight hours per day and seven days per week (five days/week for sitting at work) before calculating sitting time per domain. The total time spent sitting during the day was calculated by summing up the time spent sitting in the three domains, that is, transport, at work, and in leisure time. Again, total sitting time was calculated only in those cases for which all underlying domains of sitting were not missing. In all other cases, total sitting time was considered as missing.
Mental health was measured by the Mental Health Inventory (MHI-5), a subscale of the RAND 36 [
Using a single question, the respondents were asked whether they had paid work at the moment of the measurement. They could answer on a seven point scale with answers including “yes, as an employee (payroll),” “yes, self-employed,” “no, I am housewife/man,” “no, I am unemployed,” “no, I am retired,” “no, I am disabled,” and “other”. For the analyses, those working as an employee and self-employed were considered as a worker, while the remaining respondents, including “other,” were treated as nonworkers.
Body weight and height were measured during a physical examination by trained assistants at the Municipal Health Services with participants wearing light indoor clothing, with emptied pockets and no shoes [
Potential confounders of the association between sitting and mental health were assessed by means of self-administered questionnaires. Sociodemographic variables included gender, age (in years), and educational level. Educational level was assessed by the highest schooling achieved and was subsequently classified as low (intermediate secondary school or less), moderate (intermediate vocational or higher secondary education), or high (higher vocational education or university). Household composition was assessed by the question: “with which persons are you currently living together” using six answer categories: “not applicable,” “I live alone,” “with a partner,” “with children up to 18 years of age,” “with children 18 years or older,” “with my parents” or “with other adults”). A dichotomous variable was created to distinguish participants living alone from participants living with others. Perceived general health was measured using a question from the RAND 36 [
Data were available for 1588 men and women, aged 41 to 80 years old, examined in 2008-2009. Participants with missing values for outcome variables and confounders were excluded from the analyses (
Descriptive characteristics (mean and standard deviation or percentage) for all key variables were calculated for the study population as a whole and stratified by working status. The association between sitting time and mental health was determined using a linear regression analysis with the total or domain-specific time spent sitting as the independent variable and the mental health score as the dependent variable. Analyses were stratified by working status. Both crude and adjusted analyses were performed. To explore the role of BMI in the association, three adjusted models were applied. One included all covariates (i.e., gender, age, education, household composition, perceived health, physical activity, smoking, and alcohol) but excluded BMI (Model 1); one included all covariates and BMI (Model 2); and included an interaction term between sitting time and BMI (Model 3). The same linear regression analyses were then performed but stratified for weight status as defined by the BMI categories (healthy weight, moderate overweight, and obese adults). All analyses were performed using the SAS program, version 9.2 (SAS-Institute, Cary, NC, USA).
The mean age of the respondents was 59 years; the mean age of workers was 52 years versus 66 years for nonworkers (Table
Characteristics of the study population (
Total | Working | Not working | |
Mean ± SD | Mean ± SD | Mean ± SD | |
Age (years) | |||
Gender (% men) | 47.0 | 54.2 | 45.8 |
Education (% higher level) | 23.1 | 27.3 | 19.2 |
Household composition (% living alone) | 13.8 | 9.0 | 18.3 |
Occupational status (% working) | 48.2 | — | — |
Perceived general health (% healthy) | 86.6 | 92.4 | 81.1 |
Physical activity (h/wk)1 | |||
Physical activity (% active) | 58.9 | 61.4 | 56.6 |
Smoking (% smoker) | 17.3 | 23.0 | 12.0 |
Alcohol (% moderate consumption)2 | 55.7 | 60.8 | 51.0 |
Total sitting time (h/wk) | |||
Domain-specific sitting time | |||
Transport (h/wk) | |||
(i) Commuting or during work (h/wk) | — | ||
(ii) Leisure (h/wk) | 3.1±3.3 | ||
At work (h/wk) | — | ||
Leisure (h/wk) | |||
(i) Reading (h/wk) | |||
(ii) TV viewing (h/wk) | |||
(iii) Using computer (h/wk) | |||
(iv) Other sitting (h/wk) | |||
Mental health (score 0–100) | |||
Mental health (% healthy) | 88.6 | 90.1 | 87.3 |
BMI (kg/m2) | |||
% healthy weight | 35.6 | 41.7 | 29.9 |
% moderately overweight | 46.6 | 44.8 | 48.3 |
% obese | 17.8 | 13.5 | 21.8 |
1Total physical activity, including light-, moderate-, and vigorous-intensity physical activity;
2moderate alcohol consumption is defined as 1-2 glasses per day for women and 1–3 glasses/day for men.
No association was found for sitting during transport or for sitting at work and mental health. For time sitting during transport, there was a significant negative interaction with BMI for the working population (
The association between sitting time and mental health stratified by work status: results of the linear regression analysis.
Association with mental health1 | ||||||
Crude | Adjusted2 | Adjusted3 | ||||
Beta | 95% CI | Beta | 95% CI | Beta | 95% CI | |
Total | −0.04 | −0.05 | −0.05 | |||
Transport (h/wk) | −0.10 | −0.13 | −0.13 | |||
(i) Commuting or during work (h/wk) | −0.10 | −0.16 | ||||
(ii) Leisure (h/wk) | −0.29 | 0.04 | 0.05 | |||
At work (h/wk) | 0.04 | 0.01 | 0.01 | |||
Leisure (h/wk) | ||||||
(i) Reading (h/wk) | 0.07 | 0.15 | 0.15 | |||
(ii) TV viewing (h/wk) | ||||||
(iii) Using computer (h/wk) | −0.21 | −0.23 | −0.23 | |||
(iv) Other sitting (h/wk) | −0.28 | −0.16 | −0.16 | |||
Total | 0.04 | 0.003 | ||||
Transport (h/wk) | 0.05 | −0.14 | −0.13 | |||
(i) Commuting or during work (h/wk) | — | — | — | |||
(ii) Leisure (h/wk) | 0.05 | −0.14 | −0.13 | |||
At work (h/wk) | — | — | — | |||
Leisure (h/wk) | 0.03 | 0.01 | ||||
(i) Reading (h/wk) | 0.16 | 0.01 | ||||
(ii) TV viewing (h/wk) | −0.09 | −0.04 | −0.04 | |||
(iii) Using computer (h/wk) | 0.32 | 0.16 | 0.17 | |||
(iv) Other sitting (h/wk) | −0.05 | 0.03 | 0.03 |
1A higher MHI score indicates better mental health; thus, a negative beta indicates a negative association between sitting time and mental health; 2Adjusted for gender, age, education, household composition, perceived health, physical activity, smoking, and alcohol consumption; 3additionally adjusted for BMI; 4when added to this model:
Tables
The association between sitting time and mental health among the working population (
Association with mental health1 | ||||||
Crude | Adjusted2 | Adjusted3 | ||||
Beta | 95% CI | Beta | 95% CI | Beta | 95% CI | |
Total | −0.06 | −0.09 | −0.10 | |||
Transport (h/wk) | 0.03 | −0.03 | −0.02 | |||
(i) Commuting or during work (h/wk) | 0.03 | −0.06 | −0.05 | |||
(ii) Leisure (h/wk) | 0.10 | 0.36 | 0.36 | |||
At work (h/wk) | −0.07 | −0.09 | −0.11 | |||
Leisure (h/wk) | −0.10 | −0.11 | −0.11 | |||
(i) Reading (h/wk) | −0.05 | −0.004 | −0.02 | |||
(ii) TV viewing (h/wk) | −0.02 | −0.11 | −0.10 | |||
(iii) Using computer (h/wk) | −0.19 | −0.27 | −0.28 | |||
(iv) Other sitting (h/wk) | −0.35 | −0.34 | ||||
Total | −0.01 | −0.03 | −0.03 | |||
Transport (h/wk) | −0.15 | −0.20 | −0.19 | |||
(i) Commuting or during work (h/wk) | −0.14 | −0.20 | −0.19 | |||
(ii) Leisure (h/wk) | −0.55 | −0.35 | −0.36 | |||
At work (h/wk) | 0.10 | 0.04 | 0.04 | |||
Leisure (h/wk) | −0.11 | −0.07 | −0.06 | |||
(i) Reading (h/wk) | 0.34 | 0.46 | 0.47 | |||
(ii) TV viewing (h/wk) | −0.19 | −0.12 | −0.11 | |||
(iii) Using computer (h/wk) | −0.29 | −0.33 | −0.32 | |||
(iv) Other sitting (h/wk) | −0.17 | −0.01 | −0.03 | |||
Total | −0.08 | −0.07 | −0.04 | |||
Transport (h/wk) | −0.20 | −0.16 | −0.14 | |||
(i) Commuting or during work (h/wk) | −0.24 | −0.23 | −0.21 | |||
(ii) Leisure (h/wk) | −0.18 | 1.01 | 1.07 | |||
At work (h/wk) | 0.09 | 0.12 | 0.17 | |||
Leisure (h/wk) | −0.24 | −0.17 | −0.15 | |||
(i) Reading (h/wk) | −0.03 | 0.26 | 0.33 | |||
(ii) TV viewing (h/wk) | ||||||
(iii) Using computer (h/wk) | −0.09 | −0.09 | −0.10 | |||
(iv) Other sitting (h/wk) | −0.13 | 0.004 | 0.12 |
1A higher MHI score indicates better mental health; thus a negative beta indicates a negative association between sitting time and mental health; 2adjusted for gender, age, education, household composition, perceived health, physical activity, smoking, and alcohol consumption; 3additionally adjusted for BMI.
The association between sitting time and mental health among the nonworking population (
Association with mental health1 | ||||||
Crude | Adjusted2 | Adjusted3 | ||||
Beta | 95% CI | Beta | 95% CI | Beta | 95% CI | |
Total | ||||||
Transport (h/wk) | 0.26 | 0.13 | 0.09 | |||
(i) Commuting or during work (h/wk) | — | — | — | |||
(ii) Leisure (h/wk) | 0.26 | -0.51;1.02 | 0.13 | -0.66;0.91 | 0.09 | -0.71;0.89 |
At work (h/wk) | — | — | — | |||
Leisure (h/wk) | ||||||
(i) Reading (h/wk) | −0.14 | −0.20 | −0.17 | |||
(ii) TV viewing (h/wk) | ||||||
(iii) Using computer (h/wk) | 0.33 | 0.30 | 0.29 | |||
(iv) Other sitting (h/wk) | −0.18 | −0.15 | −0.16 | |||
Total | 0.09 | 0.08 | ||||
Transport (h/wk) | 0.07 | −0.13 | −0.13 | |||
(i) Commuting or during work /wk) | — | — | — | |||
(ii) Leisure (h/wk) | 0.07 | −0.13 | −0.13 | |||
At work (h/wk) | — | — | — | |||
Leisure (h/wk) | 0.10 | 0.10 | ||||
(i) Reading (h/wk) | 0.49 | 0.30 | 0.28 | |||
(ii) TV viewing (h/wk) | 0.04 | 0.09 | 0.09 | |||
(iii) Using computer (h/wk) | 0.38 | 0.10 | 0.09 | |||
(iv) Other sitting (h/wk) | −0.10 | 0.05 | 0.05 | |||
Total | 0.11 | 0.03 | 0.04 | |||
Transport (h/wk) | −0.21 | −0.47 | −0.46 | |||
(i) Commuting or during work (h/wk) | — | — | — | |||
(ii) Leisure (h/wk) | −0.21 | −0.47 | −0.46 | |||
At work (h/wk) | — | — | — | |||
Leisure (h/wk) | 0.13 | 0.05 | 0.06 | |||
(i) Reading (h/wk) | 0.37 | −0.04 | −0.07 | |||
(ii) TV viewing (h/wk) | 0.02 | −0.09 | −0.10 | |||
(iii) Using computer (h/wk) | 0.21 | 0.25 | 0.28 | |||
(iv) Other sitting (h/wk) | 0.20 | 0.24 | 0.31 |
1A higher MHI score indicates better mental health; thus, a negative beta indicates a negative association between sitting time and mental health; 2adjusted for gender, age, education, household composition, perceived health, physical activity, smoking, and alcohol consumption; 3additionally adjusted for BMI.
The results of this explorative study showed no association between time spent sitting during transport or sitting at work and mental health. Only sitting during leisure time and in particular the amount of time viewing TV were associated with a poorer mental health in the working population. Associations were even more complicated, because both work status and weight status are effect modifiers in these associations. Among nonworking persons, the total time spent sitting, the time spent sitting during leisure, and particularly viewing TV, was associated with a poorer mental health in those with a healthy weight only. In workers, the association between viewing TV and poorer mental health was also apparent among the obese workers only.
There are some mechanisms that may explain a relationship between sitting and the risk for poor mental health. First, the favorable effects of physical activity on mental health, especially on depression, have been well documented [
A notable finding of our study is the role of weight status with a clear association between the time spent viewing TV and poorer mental health among healthy weight nonworkers as well as among obese workers. A possible explanation for the differing associations found by weight status among workers is that obese workers consume more unhealthy food and beverages when viewing TV (compared to the healthy weight and moderate overweight workers), which may make them feel guilty, decrease their self-esteem, and negatively impact their mental well-being. However, it should be emphasized that the current status of knowledge in this field is explorative, and an obvious explanation for the present findings cannot be given. Instead, more research is necessary to investigate the relationships suggested by this explorative study before elaboration.
A few weaknesses and strengths of this study need to be highlighted. First, the data on sedentary behaviors were derived by means of self-report, which challenges reliability and validity [
In conclusion, the present explorative study confirms the relationship between TV viewing time and poor mental health as suggested in earlier studies, with BMI and working status being effect modifiers, but this association does not hold for spending time in other domains of sitting. Further longitudinal research is needed to confirm the results and to determine the causality in the relationship between sedentary behaviors and mental health. In addition, our data suggest that work status and weight status should be taken into account when studying the relationship between sitting and mental health.