Results

The majority of the subjects (1230 of the 2144 participants, 57.4%) stated that in general their self rated health had improved compared with their former residence. Some 829 subjects (38.7%) reported no change and only a proportion of 3.9% (85 participants) reported a deterioration. An overview of the sociodemographic characteristics of the sample and of the associations with an improved self rated health since having moved is given in table1.

Subjects who had moved out of the city, women, respondents with a middle education, respondents (two or more) with children and the 46 to 60 year olds were more likely to state that, in general, their self rated health had improved since they had moved. As also shown in table1, some differences across sociodemographic subgroups were also found regarding the main reason to move: “environmental reasons” were mentioned more often by persons having moved out of the city, participants with children, participants with low or middle education, and in the age groups over 30.

DIMENSIONS OF HOUSING QUALITY AND IMPROVED SELF RATED HEALTH

A factor analysis was performed to study groupings of the 40 indicators. Figure 1 shows the eight dimensions of housing quality having been identified. The label assigned to each factor intends to describe the respective dimension (fig 1). The presented model explained 48.7% of the total variance in the 40 indicators.

Improved self rated health was most strongly associated with an improved satisfaction with the two dimensions directly relating to the dwelling, namely the dimension “Apartment or building” (adjusted OR 1.55; 95% CI 1.40, 1.71) and the “Apartment related social components” (1.52; 1.37, 1.67), followed by an improved assessment of the dimension “Environment” (1.47; 1.33, 1.63) and aspects relating to “Leisure time” (1.39; 1.25, 1.55). An increased satisfaction with the dimensions “Suitability for children” (1.24; 1.04, 1.48), “Community services” (1.17; 1.06, 1.29), “Infrastructure” (1.16; 1.04, 1.28) and “Cultural and social life” (1.12; 1.01, 1.24), respectively, showed weaker associations with an improvement in self rated health since having moved.

INDIVIDUAL HOUSING QUALITY INDICATORS AND IMPROVED SELF RATED HEALTH

Table 2 shows the odds ratios for an improved self rated health associated with a higher satisfaction with the remaining 14 single indicators (out of the originally 40, see ) since having moved. The indicators are grouped according to the results of the factor analyses (see fig 1).

In the multivariate analyses, all associations were weaker than in the bivariate analyses and some associations even became borderline or non-significant. Nevertheless, five indicators remained significantly associated with an improved self rated health: In addition to the two “environmental” indicators “location of the building” and “perceived air quality” these included “suitability of the apartment”, “relationship with neighbours” and “perceived noise from neighbours”.

ENVIRONMENTAL HOUSING QUALITY INDICATORS AND IMPROVED SELF RATED HEALTH IN SUBGROUPS

Subsequently, we investigated if the associations with the two “environmental” indicators “perceived air quality” and “location of the building” were modified by the main reason to move, the type of moving or whether participants had moved from a multiple dwelling into a single family home or had become a house owner. In table 3, the results of the stratified logistic regression analyses are presented.

Among the less than 15% of participants who had moved into a single family home, improved self rated health was more strongly associated with a more favourable assessment of the “perceived air quality” than among the remaining subjects. Becoming a house owner did not change the associations materially, moreover the respective subgroup was small (results not shown).

“Type of moving” also modified the association with “perceived air quality”: among subjects having moved out of the city, the odds ratio between an improvement in self rated health and a higher satisfaction with this indicator was twice as high as among within city movers. This association was also stronger in participants who had moved mainly for environmental reasons but it was still statistically significant among those who had moved for other reasons.

When the analyses were stratified by type of moving and by main reason to move, the association between improved self rated health and a higher satisfaction with the “location of the building” was found in both types of movers, being slightly stronger in those who had moved within the city for environmental reasons. The association with an improved assessment of air quality on the other hand was only found in subjects who had moved out of the city. It was stronger in those having moved out of the city for environmental reasons but still remained significant in those with other reasons.

Discussion

Our results show that even in an economically well to do country like Switzerland, a higher satisfaction with the environmental quality of the new housing surroundings was associated with an improved well being of movers when other dimensions of housing quality and potential sociodemographic confounders were taken into account even if the subjects had not moved for environmental reasons.

IMPORTANCE OF DIFFERENT DIMENSIONS OF HOUSING QUALITY

We found that the satisfaction with the environmental housing quality, with the apartment and with the apartment related social environment were more strongly associated with wellbeing, than were infrastructure indicators, the suitability for children, and the cultural and social life. Only a limited number of previous studies are available to compare these findings with. Most of them either focused on specific aspects of housing quality and health3 4 or used different outcome or exposure measures. Van Poll found that subjective health (based on reported symptoms) was associated with dwelling satisfaction but not with neighbourhood satisfaction.31 Lawton found rather similar associations between a perceived positive change in one's life (including health) and interviewer rated ambience of the dwelling, dwelling maintenance and neighbourhood quality.11

The relative importance of different dimensions of housing quality varies probably across different cultures and social groups. Even though our finding seems plausible, the issue remains complex. Some of the dimensions and respective indicators of housing quality in our study whose associations with an improved self rated health were borderline significant would certainly deserve further investigation. It is also interesting to note that an improved relationship with neighbours and less perceived noise from neighbours, reflecting the apartment related social environment, seem to be just as important for an improved wellbeing of movers as the physical characteristics of the apartment itself.

ENVIRONMENTAL HOUSING QUALITY INDICATORS

As our research question focused on the environmental housing quality we explored this dimension in more detail. The perception of the two “environmental” indicators “location of the building” and “perceived air quality” probably differed somewhat between individuals and we suppose they stand for two slightly different aspects of the residential environment. None the less, both indicators were clearly grouped in the same factor “environment”.

The rather global environmental indicator “location of the building” seems to reflect different aspects in the more immediate neighbourhood as next to the association with environmental indicators it was also weakly correlated with, for example, suitability for children, commuting related indicators, supply with infrastructure, and social characteristics of the neighbourhood (however, correlation coefficients were all below 0.3). This indicator was associated with an improved wellbeing of movers irrespective of the destination or reason of moving. The immediate neighbourhood therefore seems to be of general importance even though we found an indication that a positively perceived change in this indicator may be more important for an improved wellbeing among subjects who had moved within the city for environmental reasons.

The indicator “perceived air quality” does not entirely reflect the objectively measurable air quality. This indicator should rather be understood as a qualitative evaluation that was also associated with other indicators of environmental quality such as greenness of surroundings as well as noise and negative effects of traffic. It can therefore also be interpreted as a proxy for “environmental quality” in a more general sense. The restriction of the association between the “perceived air quality” and wellbeing to subjects who had moved out of the city is therefore of relevance for the ongoing debate on the reasons of suburbanisation in Switzerland.25As no information on objective measures of environmental quality was available, we cannot determine from our data whether this reflects a real difference in the environmental quality between city and surrounding areas or just different perception between within city movers and out of city movers. That the former is true is suggested by the fact that air pollution was rather uniform within the city of Basel32 while somewhat lower concentrations were found at sites surrounding the city.33 Thus, the observation of a stronger association among subjects who had moved out of the city supports our interpretation of a change in satisfaction with the “perceived air quality” as reflecting a real difference in the environmental quality, as the achievable degree of perceived improvement was likely to be greater among those subjects.

That among the environmental indicators, an improved satisfaction with “perceived air quality” was most predictive of an improved self rated health certainly also reflects the current political and public debate. In Switzerland, air quality has been a main issue for several years while, for example, noise has received less public attention so far.

TYPE OF MOVING

Having moved into a single family home also increased the association between an improved self rated health and a better assessment of “perceived air quality”. However, the increase was only borderline significant and we suspect that having moved into a single family home was less influential than having moved out of the city, as only 14.9% of the total sample and 23.1% of the out of city movers actually moved into a single family home.

METHODOLOGICAL CONSIDERATION

A number of aspects are of relevance for the interpretation of the results. Firstly, it should be noted that even though the response rate was not particularly high participation bias does not seem to be a problem in our study. In most cases, non-participation was attributable to technical reasons. A comparison with data from the statistical office of the canton of Basel regarding sex, age, nationality, and type of moving showed that our sample was representative of the base population except for non-Swiss participants who were slightly underrepresented, especially in the older age groups. The educational level seemed to be rather high compared with the general Swiss population.34 However, it was to be expected that the sample might contain more subjects with a higher socioeconomic status. Inhabitants with lower education and income, especially foreigners, are more likely to have difficulties in finding new residences.35-37

As shown in the factor analysis, certain clusters of interdependent housing quality indicators were found in our data. Collinearity can lead to difficulties in separating the effects of individual indicators in a multiple regression analysis. This is a possible explanation for the observed weakening of the associations in the multivariate analyses. However, only one correlation between the 14 indicators in the final regression models exceeded 0.50 (suitability and comfort of the apartment: 0.51) and only six were above 0.30. Nevertheless, five associations remained significant in the multivariate analyses.

The simultaneous collection of the information on former and present housing quality may be a source of measurement error leading to an overestimation of the associations presented if recall bias has the same direction for prior housing quality and prior self rated health. Marans concluded however that biases introduced by dissonance reduction (that is, the tendency to avoid conflict between past action and current feelings) were not very large and that they applied rather to general evaluations than to assessments of specific attributes as presented here.38 Francescato proposed to use relative degrees of satisfaction as done in this study.39 Moreover, as the recall period in our study was relatively short, we consider it as unlikely that recall bias may have been a major source of error.

Whereas “self rated health” is a useful summary measure to study a more general concept of health, its global and subjective character does not permit us to determine which aspects of wellbeing—physical, psychical or social—are most affected by perceived improvements in the housing quality. Unfortunately, additional information on objective health measures to explore this issue further were not available. Thus, we also could not control for a change in morbidity or for a decline in functional ability in our subjects, factors that have been shown to influence self rated health.18 40 41 However, we consider changes in objective health rather as a possible intermediate step than as a potential confounder having influenced the choice of the new residence, particularly as only a small proportion of participants reported a deterioration in self rated health and less than 1% mentioned health and/or aging as main reason to move.

Even though the cross sectional design of this study does not allow for causal inference, it must be noted that we assessed the change in self rated health and the change in perceived housing quality since having moved, reflecting thus a time interval. So far, only very few longitudinal studies on changes in the satisfaction with housing quality in a broader sense and subsequent changes in wellbeing have been carried out. The few available studies included different age groups and used different dependent variables and indicators for housing quality than our study.7 11-13 Despite our own and a few other results suggesting a causal relation of housing quality on wellbeing, additional longitudinal studies with population based samples covering wider age ranges and using more detailed sets of indicators for housing quality are needed to further elucidate temporality.

Mackenbach and coworkers showed in a cross sectional study that housing problems decreased the probability of excellent self rated health.9 They suspected that this association might be an artefact of a propensity to complain because they used few general indicators to measure such a complex construct as “housing quality”.42 It seems unlikely that the specific and plausible patterns of the reported associations in our study are merely an artefact of general negativism because we used a large set of indicators and individual answering patterns varied substantially. It must also be kept in mind that all subjects in our study had moved and had done so within the same time frame. Therefore, the results cannot be confounded by a “honeymoon” reaction after a change in residence within a subsample. On the other hand, a general improvement in life satisfaction after voluntary moving that might be present in the whole sample cannot explain the heterogeneity of associations across various subgroups of movers. Certainly, subjective assessments of the environment are influenced by personal characteristics as well as by beliefs, emotions, and behavioural intentions.39 43 The individual response to an adverse environmental situation depends also on appraisal of the source and on, for example, controllability and predictability of the stressor.44 Nevertheless, if the impact of housing quality on residents' wellbeing is the target of interest, individual perception is the driving force and should therefore be of interest despite these limitations, unless one is willing to state that “the expert knows better”.

In conclusion, our results add to the understanding of a complex issue even though we could not entirely clarify which factor of the housing environment was most influential for an improved wellbeing of movers. However, we showed that perceived environmental quality is an important predictor of well being of citizens. Moreover, the significant associations between perceived improvements in the two environmental indicators “location of the building” and “perceived air quality” and an improved wellbeing in participants who had not moved for environmental reasons certainly deserve attention. Further longitudinal studies on changes of wellbeing should therefore take moving, motivations to do so and subsequent changes in satisfaction with environmental housing quality into account.