CHILDHOOD SOCIOECONOMIC STATUS AND THE METABOLIC SYNDROME

Research on social inequalities has demonstrated a clear relationship between socioeconomic status (SES) and health. Individuals of lower SES experience higher rates of all-cause morbidity and mortality than do more advantaged individuals. This relationship is not attributable solely to poor health among the most deprived individuals, but reflects a gradient of health risk extending across the full distribution of socioeconomic position existing within populations (Adler et al., 1994).

Despite the recognition of this well-established association, the underlying mechanisms by which social inequalities impair health are not well understood. Measures of socioeconomic status indicate one’s position within a broader society, and this position might affect health in various ways. Social position can determine both the availability of preventative and health promoting resources, as well as the amount of one’s exposure to health-damaging environments (Lynch & Kaplan, 2000). SES may also influence health through its association with psychological and lifestyle-associated risk factors, such as smoking prevalence and subjective distress due to more frequent stressful life events (Anderson & Armstead, 1995). In the latter regard, chronic stressors associated with social position may conceivably alter neuroendocrine functioning, resulting in later health consequences (Brunner et al., 1997).


In the following sections, several aspects of SES and health will be reviewed. First, a conceptual basis for SES research will be presented, along with information concerning the relationship of SES to cardiovascular health. The metabolic syndrome and its association with adult SES will then be discussed. Next, research on childhood SES as a predictor of adult CHD will be presented. Finally, a review of the current study will be provided, and implications of the findings will be discussed.

A conceptualization of socioeconomic status itself is necessary when attempting to explain the relationship between socioeconomic status and health. Socioeconomic status (SES) has been defined as one’s relative “position” in society, as reflected in access to or the accumulation of material resources or prestige (Lynch & Kaplan, 2000). Measures of socioeconomic position indicate particular structural locations within society (Lynch & Kaplan, 2000) and attempt to quantify an individual’s probability of success, i.e. “life chances”. Current conceptualization of socioeconomic status relies heavily on the Marxist, Weberian and Functionalist sociological traditions, as summarized by Lynch & Kaplan (2000).

A discussion of socioeconomic status must first address the concept of social class. Social class refers to groups defined by interdependent economic and legal relationships, based on an individual’s position within the economy (Krieger, Williams & Moss, 1997). Relationships between classes co-define each other, and are determined by a society’s connections through production, consumption and distribution of goods (Krieger et al., 1997). Conceptualizing class as a social relationship emphasizes how members of different social classes advance their economic and social well-being, and how the well-being of one class is linked to the deprivation of another (Krieger et al., 1997). Measures of social class attempt to capture these economic interactions among people, rather than identify the personal characteristics that determine an individual’s position within a hierarchy.
Each sociological tradition approaches social class in a slightly different way. The Marxian definition of social class reflects stratification in relation to the means of production in society. A social class is a group within a society that is relatively similar in political, economic, educational, occupational, and prestige status (Lynch & Kaplan, 2000).

According to the Weberian tradition, one's class position yields certain probabilities (or life-chances) of success. Society is stratified by class, status, and political power, and a lack of resources (i.e. goods, skills) places certain groups at a competitive disadvantage. The functionalist approach to stratification suggests that complex societies require stratification into sectors that are more or less valuable to social maintenance and progress. This position maintains that social inequality is necessitated by the need to preferentially reward, by money and power, individuals best qualified to occupy the positions of highest responsibility (Lynch & Kaplan, 2000). The sociological schools of thought described here maintain that macrosocial processes determine the socioeconomic prospects of individuals, with prevailing political and economic conditions generating hierarchies of social position.

Ignored here, however, are individual attributes, such as cognitive abilities and dimensions of personality, that covary with indices of socioeconomic status (Tomlinson-Keasey & Little, 1990). Although such individual characteristics are affected by a wide range of variables, including macrosocial factors, both personality and intelligence also have genetic bases and are influenced by idiosyncratic developmental experiences unrelated to social class (i.e. “nonshared” environmental effects). Individual differences in educational attainment, occupation, and earnings are themselves moderately heritable, and there is significant genetic covariation of SES and intelligence (Lichtenstein & Pedersen, 1997; Rowe, Vesterdal & Rodgers, 1998). Therefore, it is likely that relative socioeconomic position results from a complex interplay of the political and economic structures described in sociological thought, along with individuals’ intellectual and personality characteristics.

Although the concept of socioeconomic status has built upon these sociological traditions of social class, it is important to differentiate these two terms. Whereas social class refers strictly to social groups arising from interdependent economic relationships (i.e. “working class”, “managerial class”), current measures of SES aim to quantify an individual’s life chances of success in a social hierarchy by including both resource-based (material resources and assets) and prestige-based measures (rank or status in a hierarchy) (Krieger et al, 1997).

For example, epidemiological research in England and many other countries draws upon social class data based on the Registrar-General’s grouping of occupations, and categorizes individuals’ structural location within the economy (Marmot, Kogevinas & Elston, 1987). Because social class in this sense is conceptualized as an ordinal variable, it cannot provide a meaningful measure of distance between adjacent occupational categories, and is therefore less precise. Measures of socioeconomic status, based on composites of resource-based and prestige-based measures at an individual, household, or childhood level, in contrast, provide a more continuous measure of one’s standing in a social structure (Krieger, et al., 1997)

Most commonly, SES is assessed at the level of the individual, although household and neighborhood-level indicators are also used. The SES indicators described here are related, but not fully overlapping, and they may affect health through disparate pathways (Gallo & Matthews, 2000). Yet interestingly, disparities in health outcomes persist independently of the measure of socioeconomic status used.

The most widely reported measures of SES are educational attainment, occupational status, income, or some combination of these measures. In studying social inequalities, each measure may be seen to have both advantages and disadvantages. Individual or family income is commonly used to index SES, and can be quantified continuously or divided into categories. Income measures at any one point in time predict various health outcomes, and mortality is strongly and inversely associated with income (Kreiger et al., 1997).

Limitations of using income alone as an indicator of SES include income’s imperfect correlation with accumulated wealth and insensitivity to fluctuations in life circumstances over time. Level of education is an important marker of socioeconomic position in that it provides information about the likelihood of future success, and is also frequently an indicator of prestige.

Potential limitations of using education as a sole measure of SES include variation in the “value” of differing educational experiences defining putatively similar levels of attainment, or in how particular educational accomplishments are rewarded in a given society or economic circumstance (Lynch & Kaplan, 2000). Occupational status is useful in reflecting the prestige, income level and educational requirements associated with various positions in the economic structure, as well as in providing information about job characteristics (such as environmental and working conditions), decision-making latitude, and psychological demands of the job (Lynch & Kaplan, 2000).

Various measures of occupation categorize job types in order to reflect a particular occupational hierarchy, such as Rose and Marmot’s (1981) Occupational Grade and the Registrar General’s Classification (Szreter, 1984). One difficulty of using occupational status as a marker of social position, though, is that of quantifying change in occupational status over the life course (Krieger et al., 1997).

In sum, the intellectual traditions of Marx, Weber and the Functionalists provide a framework for research into social inequalities, and describe structural positions within society that can be measured in several ways. Interest in the associations between socioeconomic position and health has increased in recent years (Lynch & Kaplan, 2000). Most notably, the Whitehall study of mortality (Marmot et al., 1991) demonstrated a clear SES-health gradient among occupational grades of British Civil Servants. This gradient has been shown in U.S. studies as well, using both years of education (Kitagawa & Hauser, 1973) and income (Pappas, Queen, Hadden & Fisher, 1993). Advances in this body of research continue to spur efforts toward the understanding and measurement of socioeconomic variables in relation to health.