The impact of job strain on social isolation: a longitudinal analysis of French workers

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Social Science & Medicine 59 (2004) 29–38

The impact of job strain on social isolation: a longitudinal analysis of French workers Michel Ve! zinaa,*, Francis Derriennicb, Christine Monfortc a

Department de Medicine Sociale et Preventive, Cite Universite, Universit!e Laval, Qu!ebec, Canada b Inserm U-88, Paris, France c Inserm U-435, Rennes, France

Abstract Numerous studies have shown that work may have an impact on social identity and social functioning in the community. Since work organisation in our society has gone through some profound changes in the last few decades, it is important to study the effect of these new constraints on the social life of people and, thereby, on their health. Using data from a French longitudinal cohort study on work, health and ageing (ESTEV), this paper analyses the impact of job strain on social isolation, in a sample of 16,950 individuals who were working in 1990 and 1995. The results show that low-decision latitude was associated with a significantly higher level of social isolation in both men and women. When compared with low job strain, active work (high-psychological demand and high-decision latitude) and high job strain were associated among men with a significantly higher level of social isolation. This study shows that a change in psychosocial work conditions (demand and control) had an impact on social isolation and that this impact may be more significant in male workers than in female workers. r 2003 Elsevier Ltd. All rights reserved. Keywords: Work organisation; Psychosocial factors; Decision latitude; Psychological demand; Social isolation; Job strain,Gender differences; France

Introduction Work plays an essential and well-known role in social integration. Work allows us to take part in shared experiences and become involved in activities whose objectives go beyond our personal interests. Above and beyond its economic aspect, work helps us acquire a social status that determines our social identity and our place in society. Work likewise helps us to fulfil ourselves and to structure our identities, thereby reinforcing our self-esteem and confidence in our abilities (De Bandt, Dejours, & Dubar, 1995). Conversely, it is equally true that being deprived of work influences the way we see ourselves and the way others see us.

*Corresponding author. Fax: +1-418-656-7759. E-mail address: [email protected] (M. V!ezina).

The social integration that occurs at work also contributes to greater social participation. Indeed, in comparison to those who are without work, employed people have access to a greater number of social networks, groups and associations, thereby increasing their interactions with others. People who are more socially active have more confidence in others and a stronger feeling of control over their environment, both of these being elements that strengthen the social capital of communities (B!elanger, Sullivan, & S!evigny, 2000). On the other hand, many studies have also demonstrated that the work environment can have a negative impact on life outside the workplace. Back in the 1950s in France, Le Guillant, Roelens, B!equart, and Lebreton (1956) described what they called ‘‘La ne! vrose des t!el!ephonistes’’ (phone operator neurosis). One characteristic of this neurosis was the fact that these workers, when faced with tight time constraints outside their work, incorrectly and spontaneously used work-related

0277-9536/$ - see front matter r 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.socscimed.2003.09.033

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words or sentences. For example, when someone talked to them abruptly, they would respond ‘‘Hello, one moment please’’ or ‘‘Hello, what number?’’. This phenomenon was described as a contamination of everyday language by occupational expressions. More recently, studies in the psychopathology of work have demonstrated how monotony arising from time constraints and the Taylorian organisation of work influences the psychic functioning and social life of workers (Dejours, 1990). Workers who must wrestle with their thoughts so as not to upset the proper functioning of their activities or disturb their work rhythm are obliged to use certain defensive strategies. The goal of these strategies is to paralyse the workers’ spontaneous psychic activity, potentially resulting in a saturation of the field of consciousness when the work pace is increased. Because this psychic repression is difficult to achieve, many workers prefer to remain in this state during the weekends and holidays so as to avoid the costly effort of recreating psychic anaesthesia upon returning to work. This results in a state of mindless inertia in which workers, cut off from their spouses and friends, prefer solitude to ordinary social life. The effects of job conditions on personality and social orientation have also been demonstrated by Kohn and Schooler (1982). These authors have shown that ‘‘occupational self-direction’’, namely the use of initiative, thought and independent judgement in work, leads to self-directed orientations to self and society. Men who are self-directed in their work are consistently more likely to become non-authoritarian and self-confident, to become less self-deprecatory, fatalistic, anxious and conformist in their ideas, and to develop higher moral standards. Finally, a relation between passive work (low-decision latitude) and a decrease in social leisure activities has been established by Karasek (1976). The negative longterm result of this relation has been interpreted by Karasek as having the potential to undermine people’s capacity for social relations, leading them in turn to withdraw from democratic participation. ‘‘Overall, the finding that political participation declines as jobs become passive implies a gradual withdrawal from political participation by the majority of workers, and an increasingly dominant role in decision making by the few who retain active work opportunities in their jobs’’ (Karasek, 1997). In the last few decades, work in our society has gone through profound changes which have made it more intense and precarious (Gollac & Volkoff, 1996; European Foundation, 1998; DARES, 1998; Kauppinen, 1999; B!elanger et al., 2000). Consequently, the question arises as to whether the effect of these new constraints is not to impoverish people’s social lives and, thereby, their health. If this is true, research must look

beyond the simple fact of being employed and seriously consider work organisation constraints. Though several models can be used to measure psychosocial conditions at work, Karasek’s demandcontrol model would seem to be particularly useful. This model is based on the hypothesis that a work situation that is characterised by a combination of high psychological demand and low-decision latitude can increase a person’s risk of developing physical or mental health problems (Karasek, 1979; Karasek & Theorell, 1990). The term psychological demand refers to the amount of work to be carried out, the mental demands involved and the associated time constraints. The term decision latitude refers to the capacity to make decisions about one’s own work and, especially, to the opportunity to be creative and to use and develop one’s abilities. The combination of low-decision latitude and highpsychological demand is referred to as job strain. This situation increased in Europe from 1991 to 1996, where it went from 25% to 30%, according to the results of studies conducted by the European Foundation for the Improvement of Living and Working Conditions (European Foundation, 1997). Similarly, in 1998 in Qu!ebec, 62% of women and 51% of men had a lowdecision latitude as compared with 50% and 40% in 1992–1993 (Bourbonnais, Brisson, Larocque, & Vezina, 2000, chapter 23). In addition to cardio-vascular disease and musculoskeletal problems (Ve! zina, 1999; Tubach, Leclerc, Landre, & Pietri-Taleb, 2002; Kivim.aki et al., 2002), job strain as defined in Karasek’s model has likewise been associated with mental health problems, most notably depression, psychological distress, burnout and increased consumption of psychoactive drugs (Karasek, 1979; Landsbergis, 1988; Braun & Hollander, 1988; Sauter, Murphy, & Hurrell, 1990; Landsbergis, Schnall, Deltz, & Friedman, 1992; Stansfeld, North, White, & Marmot, 1995; Bourbonnais, Brisson, V!ezina, & Moisan, 1996; Bourbonnais, Comeau, Dion, & Vezina, 1998; Moisan et al., 1999). Decision latitude, as defined in Karasek’s model, explains more than half of the gradient of well-being and depression associated with hierarchical status among London civil servants interviewed in the Whitehall II study (Stansfeld, Head, & Marmot, 1998). Moreover, low-decision latitude has been associated with an increase in the risk of mortality during one’s working life (Amick et al., 2002). It has also been associated with a greater tendency to control one’s spouse (Stets, 1995). Finally, a link between emotional reactions and certain aspects of work organisation that are typical of job strain was likewise demonstrated using data collected in a representative cohort of French workers (ESTEV Study: Derriennic, Touranchet, & Volkoff, 1996) that included more than 20,000 subjects who were followed longitudinally between 1990 and 1995 (Derriennic, V!ezina, & Monfort, 2001, chapter 10).

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Methods

1995, 18,695 people, or 87% of the subjects who participated in the first study, also participated in the second. The present study looks solely at the 16,950 subjects who participated in 1990 and who were still working 1995. This allowed us to compare the evolution of the psychosocial work factors with those of social isolation while avoiding any bias related to exclusion from work.

Sample description

Social isolation and work condition questionnaires

The ESTEV study was established to examine how health conditions evolve as people age and to shed light on the role of work conditions in this evolution (Derriennic et al., 1996). This longitudinal study was conducted between 1990 and 1995 on a random sample of the working population in 7 French regions that are characteristic of French industrial sectors. The generation gap was controlled for by randomly selecting the sample from exhaustive lists of workers who were born in 1938, 1943, 1948 and 1953 and who were consulting the 400 occupational health physicians who voluntarily participated in the study. All workers in France must, by law, have a yearly medical examination, with the exception of farmers and civil servants. The data collection took place in 1990 and 1995 during the annual work medical examination. The same data collection protocol was used both times. An occupational health physician administered a medical questionnaire during the examination. The subjects also filled out, before the examination, two self-administered questionnaires, one about work and the other about perceived health. The number of subjects examined in the ESTEV study between 1990 and 1995 is shown in Table 1 according to their job status and their situation with respect to the initial cohort. In total, 21,378 workers, or 88% of the target sample, were queried in 1990. Participation was practically identical according to age, sex and region. Women accounted for 8998 of the total participants. In

This study used the social isolation (SI) dimension of the French version of the Nottingham Health Profile (NHP). The NHP is a series of 38 dichotomous items to which subjects respond (Bucquet, Condon, & Ritchie, 1990). These items are grouped together in six distinct dimensions, including the social isolation dimension, which is composed of four questions. The items of this latter dimension refer to feeling alone, finding it difficult to establish contact with others, having no one close with whom to talk and having difficulty in getting along with others. Subjects were considered to be socially isolated as soon as they presented at least two of the four items in the SI dimension. Two items corresponds to the next integer number when we round up the mean number of positively answered items among people who answered at least one question positively during the first phase of the study in 1990. Accordingly, in order to evaluate the appearance or incidence of new cases of social isolation in 1995 among those who said they were not isolated in 1990, we considered the number of subjects who responded positively to two or more items in 1995 but to only one or fewer in 1990 (i.e. subjects free of SI in 1990). As concerns the organisation of work, our selfadministered questionnaire allowed us to evaluate the two fundamental psychosocial factors of the Karasek model, namely decision latitude and psychological demand. Decision latitude was defined to be high as soon as a person answered ‘‘yes’’ to at least two of the

The specific objective of the present paper is to examine the latter study’s data in order to determine the extent to which work organisation affects the social implication of people, and, more generally, to analyse the links between work life and social life.

Table 1 Number of subjects examined in the ESTEV study according to their situation in 1990 and 1995

Men Women Total a

Subjects who participated in 1990a

Subjects lost to follow-up in 1995

n1

n2

% (n2 =n1 )

n3

% (n3 =n3 þ n4 )

n4

% (n4 =n3 þ n4 )

12,450 8928 21,378

1661 1022 2683

13.3 11.4 12.6

9787 7163 16,950

90.7 90.6 90.7

1002 743 1745

9.3 9.4 9.3

Subjects who participated both times Employed in 1990 and 1995

In 1990, all the subjects in this table were actively employed workers.

Employed in 1990 and unemployed in 1995

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following three items: ‘‘there is room for learning in my work; my work varies; I can choose how to do my work’’. In the same way, psychological demand was defined to be high as soon as a person answered ‘‘yes’’ to at least two of the following three items: ‘‘I have to work fast; I have to do several things at once at work; I’m often interrupted at work’’. Combining these two factors, we can define four types of exposure ranging from low strain (low-psychological demand and highdecision latitude) to high strain (high-psychological demand and low-decision latitude), with two intermediate exposures: passive work (low-psychological demand and low-decision latitude) and active work (highpsychological demand and high-decision latitude). Using data from a research project currently underway in northern France, we have been able to evaluate the validity of our work condition questionnaire by comparing it to Karasek’s (Edme, Leroyer, Derriennic, & Ve! zina, 2003). These comparisons show that, for both psychological demand and decision latitude, more than 68% of the subjects were correctly classified. It also shows that our decision latitude measure is more restrictive than Karasek’s, 30% of the subjects being wrongly classified as not having low-decision latitude (false negative when compared to Karasek’s). However, for psychological demand, our questionnaire is less restrictive, classifying 29% of the subjects as false positive (when compared to Karasek’s). None of these results are modified by the age, gender or socioeconomic status of the participants. It is noteworthy that even though there were only three questions (instead of the nine in Karasek’s questionnaire) to measure each of the two fundamental components of the model, each of the dimensions of these two components was measured in the same proportions. It was therefore not surprising to see that, for both decision latitude and psychological demand, less than 3% of the subjects were identified by one questionnaire but not by the other.

health1 problems as evaluated by an occupational health physician. Statistical analysis The analyses were conducted systematically for each of the two sexes, since the same factors can conceal different realities depending on gender. We began by conducting bivariate analyses of the associations between SI (both for prevalence and incidence) and the change status from 1990 to 1995 in the psychological factors. These associations were tested with the Mantel-Haenszel chi-squared test adjusted for year of birth. Analyses of the predictor effect of the psychosocial factors in 1990 were conducted separately for the entire sample for prevalence, and for the subjects free of SI in 1990 for incidence. In each case, two analyses were performed using multivariate logistic regression models with social isolation as a dependant variable: one analysis with psychological demand and decision latitude as explanatory variables and another analysis with job strain as the explanatory variable. The other variables that were adjusted were the confounding variables cited above. We recognised that these variables could be intermediate variables and, consequently, could introduce an over-adjustment. This was mainly the case for pain and disability (mobility problems) across the corresponding dimensions of the NHP indicator. However, the pain dimension is not solely limited to musculoskeletal pains. The two dimensions, pain and disability, were thus not redundant. These variables were therefore kept in the pool of confounding variables to obtain a more conservative model. Only the results related to the main psychosocial variables of this study are presented in the tables. All associations were tested with bilateral tests at the 5% significance level.

Results Other measures Other professional factors were measured, namely, physical demand at work (indicator built by combining the carrying of heavy loads, exposure to difficult positions and vibrations, and physical effort with tools) and staggered work hours (having to work early mornings, evenings, nights or shift work at least 50 days a year). Age, education level and marital status were added to these confounders so as to consider the individual characteristics that might affect the subjects’ declarations. In order to take into account personal health problems that can contribute to a decrease in social activities, we controlled for the effect of pain (NHP-8 items) and a reduction in physical mobility (NHP-8 items) as evaluated by the subject, as well as for

As concerns work psychosocial factors, 33% more women than men stated they had low-decision latitude. This figure remained relatively constant between 1990 and 1995, i.e. 18% for men and 24% for women. A slight rise in the prevalence of subjects exposed to low latitude was observed as seniority increased among both men and women. The declarations of high psychological demand likewise remained stable between 1990 and 1995, hovering around 54% for men and 57% for women. There was, however, a slight increase for people born in 1938, that is for those who went from 52 to 57 years old from 1990 to 1995 (data not shown). 1 The diseases were identified in keeping with the International Classification of Diseases (ICD-9).

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As can be seen in Tables 2 and 3, the adjusted prevalence and incidence of social isolation in 1995 in relation to psychosocial work constraints in 1990 and 1995 was almost two times higher among women than among men. Except for the SI prevalence in the case of exposure to high job strain, this ratio holds true

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whatever the variations in psychosocial constraints between 1990 and 1995. Moreover, for both men and women and after adjusting for age, the prevalence and incidence of SI were mainly related to the presence or absence of decision latitude in both 1990 and 1995. Prevalence and incidence decreased when there was

Table 2 Adjusted prevalence of social isolation in 1995 and psychosocial work constraints in 1990 and 1995 Psychosocial constraints

Social isolation (%) 1990

1995

Men %

Psychological demand

Low High Low High

Low Low High High

3.4 4.2 3.9 4.5

Decision latitude

High Low High Low

High High Low Low

3.0 5.8 6.3 7.9

Job strainb

Low Low High High

Low High Low High

2.4 7.4 7.1 11.2

Women a

p

% n.s.





pa

8.3 7.4 8.2 7.1 6.1 9.5 11.1 10.9 5.1 7.9 9.7 12.8

n.s





 po0:001; n.s.=not statistically significant. a Mentel-Hentzel chi-squared test adjusted for age. b High job strain=high-psychological demand and low-decision latitude.

Table 3 Adjusted incidence of social isolation in 1995 and psychosocial work constraints in 1990 and 1995 Psychosocial constraints

Social isolation (%) 1990

1995

Men %

Psychological demand

Low High Low High

Low Low High High

2.5 2.7 2.8 2.9

Decision latitude

High Low High Low

High High Low Low

2.3 3.3 3.8 5.1

Job strainb

Low Low High High

Low High Low High

1.9 2.7 2.6 5.2

 po0:001; n.s.=not statistically significant. a Mental-Hentzel chi-square test adjusted for age. b High-job strain=high-psychological demand and low-decision latitude.

Women pa

% n.s.





5.7 4.7 5.7 4.5 4.1 6.7 7.1 7.0 3.7 7.1 7.9 9.7

pa n.s.





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New cases (incidence) of social isolation were thus not only related to the characteristics of work organisation in 1990 but also to their changes between 1990 and 1995. It is also worth noting, primarily among women, that the loss of decision latitude in 1995 would seem to have had a fairly permanent effect in terms of social isolation. In order to better determine the specific effect of psychosocial constraints on social isolation, a logistic regression was used to conduct a multivariate analysis of the predictive role of the different factors that can influence it. The analysis indicated that the prevalence (Table 4) and incidence (Table 5) of SI were related, for

high-decision latitude, whereas they varied little in relation to changes in psychological demand. It is noteworthy that the distribution of SI prevalence as a function of job strain was as expected for both men and women: the absence of strain in 1990 and 1995 (lowpsychological demand, high-decision latitude) was related to low-social isolation. When the absence of job strain was compared to its presence in 1990 and in 1995, a sizeable gap differentiated the various cases. The results presented in Table 2 show that the prevalence of social isolation depends on both the past (job strain in 1990) and the present (job strain in 1995).

Table 4 Relationships between psychosocial work factors in 1990 and the prevalence of social isolation in 1995 for each sex (logistic regression)a 1990 Factors

Prevalence Men

Psychological demand

Decision latitude

Job strain

Women

OR

CI

OR

CI

Low High

1 1.7

(1.4–2.1)

1 1.0

(0.8–1.2)

High Low

1 1.7

(1.4–2.2)

1 1.3

(1.1–1.6)

Low High Passive Active

1 3.0 1.7 1.7

(2.0–4.3) (1.2–2.4) (1.3–2.2)

1 1.2 1.4 1.0

(0.9–1.7) (1.1–1.8) (0.8–1.3)

OR: odds ratio is an indicator used to measure relative risk; CI: confidence interval of 95% of the odds ratio. a

Adjusted for these factors in 1990: age, education, staggered work hours, physical demand at work, marital status, presence of pain, physical mobility problems and current pathologies.

Table 5 Relationships between occupational factors in 1990 and the incidence of social isolation in 1995 for each sex (logistic regression)a 1990 Factors

Incidence Men

Psychological Demand

Decision Latitude

Job Strain

Women

OR

CI

OR

CI

Low High

1 1.4

(1.1–1.9)

1 0.9

(0.7–1.2)

High Low

1 1.5

(1.1–2.0)

1 1.3

(1.0–1.7)

Low High Passive Active

1 2.0 1.6 1.5

(1.2–3.3) (1.1–2.4) (1.1–2.1)

1 1.1 1.4 1.0

(0.8–1.7) (1.0–1.9) (0.7–1.3)

OR: odds ratio is an indicator used to measure relative risk; CI: confidence interval of 95% of the odds ratio. a Adjusted for these factors in 1990: age, education, staggered work hours, physical demand at work, marital status, presence of pain, physical mobility problems and current pathologies.

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both sexes, to the ‘‘decision latitude’’ component of the Karasek model, even after adjusting for psychological demand, age, education, staggered work hours, physical demand at work, marital status, presence of pain, physical mobility problems and current pathologies. The psychological demand component was only associated with social isolation among men. Thus, lowdecision latitude among men and women and high psychological demand among men were associated with an increase in SI ranging from 30% to 70% for both prevalence and incidence. Moreover, using the same type of logistic regression model, while substituting the ‘‘job strain’’ factor for the two specific factors, namely ‘‘decision latitude’’ and ‘‘psychological demand’’, the odds ratio related to high job strain in men (reference: low job strain) was 3.0 for SI prevalence and 2.0 for SI incidence. This signifies that the presence of job strain in men in 1990 was associated with two times more social isolation in 1995 than when they were not exposed to this occupational constraint. In women, high strain was not associated with social isolation. Furthermore, the significant association observed with passive work (lowpsychological demand and low-decision latitude) was of the same nature as that observed with low-decision latitude taken alone.

Discussion The results of the ESTEV study clearly indicate that low-decision latitude at work is associated in both men and women with a greater risk of social isolation, as measured by the NHP, an indicator whose reliability and validity are widely acknowledged (Hunt et al., 1980). They also show that, when compared to low job strain, high job strain and passive and active work were associated among men with a significantly higher level of social isolation. These results are coherent with other research carried out in Europe, the United States and Qu!ebec. Indeed, a prospective study conducted with 20,000 American nurses from 1992 to 1996 showed that decision latitude at work, as measured by the Karasek questionnaire, explained half the drop in the social functioning of the participants, as evaluated by the SF-36 questionnaire. This effect was independent of age, physical effort at work, job status, alcohol or tobacco consumption, physical activity, body mass, chronic illness, marital status and education level (Cheng, Kawachi, Coakley, Schwartz, & Colditz, 2000). It is noteworthy that the ‘‘social functioning’’ component of the SF-36 questionnaire is well correlated with the ‘‘social isolation’’ dimension of the NHP (Stansfeld, Roberts, & Foot, 1997). A significant relationship was established in the Que! bec health survey between, on the one hand, lowdecision latitude and, on the other, a low level of social

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support and a lesser degree of satisfaction about one’s social life (Bourbonnais et al., 2000). Moreover, other studies have demonstrated a significant association in both men and women between decision latitude and the frequency of physical activity (Hellersted & Jeffery, 1997). In men, sedentariness was also associated with low-decision latitude (Brisson, Larocque, Moisan, V!ezina, & Dagenais, 2000). With regard to the impact of job strain on social isolation, we measured the relationship between occupational factors in 1990 and 1995 and the incidence of social isolation in 1995, adjusted for the same factors that are mentioned in Table 5. The results show that the disappearance of job strain in 1995 is associated among women with a decrease in social isolation when compared to those having high job strain in 1990 and 1995 (data not shown). This is coherent with a previous study that showed that cumulative high job strain exposure over a 2-yr interval is associated with higher systolic blood pressure when compared to women exposed to high job strain at only the beginning or end of the interval (Laflamme et al., 1998). Even though these results are coherent and reinforce those of other studies of diverse categories of workers using different indicators, the implication of these results must nonetheless be determined and possible biases pointed out. For example, the ESTEV sample only deals with workers who were seeing an occupational health physician. This excludes farmers and civil servants. Furthermore, not all ages of workers are represented since the study did not include people who were under 37 or over 52 years of age as of 1990. The implication of the results is thereby limited to the second half of work life. The very high rate of participation (88% in 1990 and 87% in 1995), which remained stable with respect to age and sex, limited the potential for bias due to nonparticipation. Despite the fact that the cohort members were randomly selected, we cannot exclude a selection bias, given the fact that the occupational physicians participated on a voluntary basis and that only 7 regions, representing 40% of the French population, were covered by the project. On the other hand, we can say that the effect of this bias is probably not very important because a complementary analysis showed that the distribution of the sampled workers by sex, age and socio-economic category did not differ from that obtained from the national French statistics (excluding farmers and civil servants). Conversely, by proceeding with a temporal separation of occupational factors (those of 1990) and effects (SI in 1995), the bias due to the ‘‘subject’’ factor may be considered to have been minimised, in particular in the predictive and incidence analyses. Indeed, it is highly unlikely that subjects answered the NHP in 1995 based on the answers they gave five years earlier to occupational variable items.

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Moreover, even if we were able to control for the effect of several individual characteristics, including age, socio-economic level and marital status, the present research may have certain limits in this regard. For instance, we were not able to take into account the different types of personality that can have an effect on social life outside of work. This being said, other studies have controlled for this individual characteristic and have still found an association between decision latitude and a decrease in social leisure activities (Karasek, 1976). Moreover, the statistical analyses used in our study allowed us to exclude the hypothesis that social isolation could be explained by the presence of individual diseases or other occupational exposures like physical demand or shift work. Controlling for these confounders highlighted the pathogenic character of the work organisation dimensions studied here. For example, when we did not control for the presence of pain or for mobility problems, we found an increasing risk of social isolation, which probably signifies that pain and disability are intermediate variables (data not shown). All told, the associations between decision latitude and psychological demand on the one hand and social isolation on the other do not appear to be secondary phenomena. They might even be under-evaluated if we consider that the study only focused on people who were seen twice at work, i.e. those who were in good enough health to keep working. Furthermore, this ‘‘healthy worker effect’’ is not without significance if we take into account that the people who were excluded from the work force or who were lost to follow-up in 1995 were two times more likely to suffer from social isolation in 1995 than in 1990. As this example shows, the main strength of this study resides in its longitudinal component. This component highlights the possible ‘‘cause and effect’’ link between the evolution, over a five-year period, of exposure to decision latitude and psychological demand on the one hand and the appearance of social isolation on the other. To better demonstrate the existence of a real link between low-decision latitude and social isolation, we have to be able to refer to under-lying mechanisms that might explain the psychological or sociological plausibility of such an association. The first explanation might come from stress theories, which state that stress can bring about a decrease in some of our cognitive abilities. Thus, people might react to stressful situations by having difficulty in learning new things, in concentrating, in memorising and in being creative (Levi, 1997). The weaker effect of psychological demand on social isolation in women requires deeper analysis of women’s work situations. Aside from differences in domestic and family responsibilities, the gender-based division of work leads women to hold different jobs than men. Furthermore, even when men and women have the same job title, they often have different tasks and levels of job

control (Messing, Dumais, Courville, Seifert, & Boucher, 1994; Brisson, 2000). Occupations held predominantly by women are generally characterised by repetition, monotony and less creativity (Messing, 1997; Mathews, Hertzman, Ostry, & Power, 1998). Given this, even when psychological demand is measured with the same questionnaire, it can encompass different realities in men and women’s work and may, thereby, have different impacts on social isolation. Accordingly, job strain may be a more significant determinant of social isolation in male workers than in female workers, as is also the case for psychological well-being (Vermeulen & Mustard, 2000). Another possible explanation is related to men and women’s different socialising patterns. Research on social support suggests that women’s networks are generally more supportive than men’s (Russell, 1999). Women are also more inclined to have a close friend or family member, other than their spouse, in whom they can confide (Antonucci, 1994). Women report more close persons in their primary networks (Fuhrer, Stansfeld, Chemali, & Shipley, 1999) and they find it easier to mobilise their support network when in need (Belle, 1989). Accordingly, the national health survey that was recently conducted in Quebec (Canada) showed that social support outside work is higher for women than for men. This is especially true when women are exposed to low-decision latitude, whatever the demand level (i.e. both high strain and passive jobs) (Bourbonnais et al., 2000).

Conclusion The results of the analysis of the ESTEV study data support, through a longitudinal 5-yr approach, the socially pathogenic nature of work when it is monotonous (i.e. no variation or learning possibilities) or rigid (i.e. no potential for choosing one’s own methods). These harmful consequences were more substantial for men when they had to work fast, do several things at once or be interrupted often in their work. This form of ‘‘social pollution’’ (Dejours, 1990) has a major impact because of its repercussions on public health and political life. Public health suffers in particular due to the deterioration that occurs in a community’s social capital (Kawachi, Kennedy, Lochner, & Prothrow-Stith, 1997; Kawachi, Kennedy, & Glass, 1999) and social ties (Corin, 1996). Political life suffers through a reduction in people’s participation in the community’s democratic process (Karasek & Theorell, 1990). These conclusions are particularly important in the current French context of the rearrangement and reduction of work hours. Work risks are becoming more frequent, due to a decrease in breaks and informal exchanges, and more intense, because of the onus on

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