Assessing the social class of children from parental information to study possible social inequalities in health outcomes
Introduction
Much evidence of a relationship between health level and social or socio-economic factors has been found (1). This link has been observed in several health outcomes such as mortality (2), survival during childhood (3), the proportion of chronic health problems present in a population (4), several anthropometric indexes (5), risk factors during childhood (6), and the subjective perception of health status (7). Even the severity of disease is influenced by socio-economic status 8., 9..
Social class is an important tool when measuring the “total impact” of most variables that characterize the social environment in the life of individuals. It is not easy to assess social class, since it is not a directly measurable feature. It is usually assessed from either occupation (10), level of education (11), or level of income (12). Many methods can be found in the scientific literature (13), all of which try to address the intrinsic difficulties underlying the assessment of social class, but most use only one of the above three attributes. When there is information on all three factors, these should all be considered together, although it can be difficult to combine them to assign an individual to a social group. In the case of a childhood population, the assessment becomes even harder, since they do not work, have no income, and their educational level is strongly related to their age. Therefore, the information must be taken from their progenitors and several approaches have been proposed for obtaining an indicator of social class for home or family (14). Most approaches suggest taking either the father or the mother as a gauge of the family's social class, or the dominant one between both (method of neutral gender). However, relevant information is missed, introducing bias that can make results unreliable, which could explain why the results obtained are different when the family's social class is based on information from either the father or the mother. Both parents contribute and neither can be discarded. The issue then becomes on how to find a way to properly combine them, and correspondence analysis is a suitable candidate.
Correspondence analysis is a statistical technique for analyzing categorical data. It is widely used in social sciences, and has been implemented in all statistical packages. Starting from a table where rows represent individuals and columns represent categorical variables so that cell i,j is the response of individual i to question j, correspondence analysis reduces the dimension of the table and extracts all relevant information by means of the different scores obtained from the information stored in the table. Usually, there is no limit to the number of variables. In our context, this means that for any individual, information on occupation, education, and income can be jointly considered to extract a unique score indicating his or her social class. In the case of a childhood population, the data from both parents can be pooled to provide a score as an index of social class, trying to include as much information as possible in the reduction of the two parents' indicators into one. Furthermore, non-economically active people such as the unemployed or housewives can be included in the analysis assessing their social level also.
In this study, we propose correspondence analysis as a new method for obtaining a measurement of social class, and applying it to study the influence of social class on children's oral health in the Comunitat Valenciana, an autonomous region of Spain. We also perform the analysis with the classical methods mentioned above to compare results.
The association between social class and oral health is well-documented 15., 16., 17., 18., 19., 20., 21., 22., 23., 24., 25. and has been analyzed with various indexes for both features. Some studies were conclusive and others were not (26).
A wide variety of measures of oral health have been used to explore its association with social class. To mention a few: caries prevalence (25), index of teeth with decay, missing or filled (DMF-T) (15), index of dental surfaces with decay, missing or filled (DMF-S) (27), community periodontal indexes of treatment needs (CPITN) (28), and habits of dental hygiene (29).
In this study we will take the results of a correspondence analysis as an index of social class and will use all the oral health indexes mentioned above to assess the influence of a child's social class on their oral health status. We will also check this association against the social classification provided by other standard methods and compare results.
Section snippets
Methods
Between October and December 1998, a cross-sectional study was performed to assess the dental health status of the Comunitat Valenciana (4,009,309 habitants in 1998), one of the seventeen autonomous regions of Spain. The target population was 6-, 12-, and 15–16-year-old school children attending schools in the region. The sampling design was a two-stage cluster sampling. The primary sampling units were schools placed in the Comunitat Valenciana sampled following probability proportional to
Results
The distribution by social class of 933 children in the study for each method of allocation is shown in Table 2. We can see that low class is the most frequent one in all approaches, except for the MOTHER method. High social class shows a greater number of individuals than middle social class for FATHER, MOTHER, and MAXIMUM methods, whereas the opposite happens for CORR1 and CORR2 methods. The MOTHER method classifies most children in the miscellaneous class, whereas the other approaches
Discussion
Evaluating the performance of a method for social class assessment is not a simple task. Authors can subjectively judge whether or not a method classifies individuals in social groups in a sensible way. However, subjective criteria based on personal experience cannot often be translated into scientific arguments, and whether objective criteria exist or not, authors must agree to some degree with the resulting classification for the method to be considered adequate.
Most methods of social class
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