Agricultura y quema

A life course approach integrates aspects of each of the above explanations and posits that a number of different social, psychological, and biological factors accumulate and interact across the life course to produce the social gradient in health and wellbeing (Bambra, 2012; Smith et al., 1994). In particular, life course researchers are interested in understanding how certain exposures, such as disadvantaged socioeconomic conditions during childhood, get ‘under the skin’ and into the biology and psychology of older individuals and subsequently result in adverse health events and lower psychological wellbeing (Ferraro & Shippee, 2009). In life course epidemiology, a number of empirical models have been developed that help to uncover specific social processes underlying life course influences on health (Kuh et al., 2003). These provide a useful framework for understanding potential life course influences on quality of life in early old age, but have been criticised for their weak theoretical underpinning (Netuveli & Bartley, 2012). In the following chapter, the literature on the evidence relating to the influence of life course socioeconomic position on quality of life is systematically reviewed in relation to these models. It should be noted that the models (described below) are not intended to be competing explanations and they are indeed difficult to separate both theoretically and empirically (Bartley & Blane, 2009; Blane et al., 2007b; Hallqvist et al., 2004).

1.5.6.1 Life course models

The key social processes thought to underlie the influence of life course socioeconomic position on later health outcomes are latent, pathway, and cumulative effects (Ben-Shlomo & Kuh, 2002; Pollitt et al., 2005). Figure 1.2 summarises the latent, pathway, and cumulative processes. In brief, a latent effect supposes that childhood socioeconomic position has a direct influence on health (path a). Under a pathway model childhood socioeconomic position is thought to influence health, indirectly, through adulthood socioeconomic position (path b x c). A cumulative effect (path a + c) may result from the additive influence of both childhood and adulthood socioeconomic position on health (Ploubidis et al., 2014). Social mobility can also be considered as a separate process that

may underlie the influence of socioeconomic position on health (Pollitt et al., 2005). It suggests that the movement from one socioeconomic position to another may be detrimental or protective to later health, on top of the prior and current experience of a low or high position (Houle, 2011).

a = latent effect b x c = pathway effect a + c = cumulative effect

Cumulative effects

A key social process thought to contribute to socioeconomic inequalities in health and wellbeing is the accumulation of advantage and disadvantage across the life course.

Socioeconomic advantages and disadvantages (as well as other adversities) tend to cluster both cross-sectionally and longitudinally (Bartley & Blane, 2009). For example, high parental education and affluence during childhood increases the chance that a child achieves a high education level, continues into a professional occupation, inherits wealth from family, and receives an occupational pension in retirement, which leads to a

reduced risk of adverse health outcomes. The accumulation of advantage and disadvantage across the life course has been shown to influence a range of health outcomes, including limiting long-term illness, self-rated health, adverse cardiovascular events, and psychological health (Bartley & Plewis, 2002; Kjellsson; Ljung & Hallqvist, 2006; Luo & Waite, 2005; Pollitt et al., 2005).

Childhood socioeconomic

position

Adulthood socioeconomic

position

Health outcome a

b c

Figure 1.2 Diagram of the hypothesised relationships between life course socioeconomic position and health. Adapted from (Ploubidis et al., 2014).

Researchers usually test this theory by summing socioeconomic exposures over the life course (Pollitt et al., 2005) and investigating whether a dose-response relationship is observed between the exposure and outcome (Singh-Manoux et al., 2004). Under this theory, no period of the life course is considered crucial for the outcome under

investigation. Rather, it is experiences over the whole life course that accrue and affect later health and wellbeing. A difficulty with this approach is that socioeconomic

exposures across the entire life course are rarely collected in surveys, therefore, it is unlikely that the true degree of exposure to socioeconomic advantage or disadvantage over the life course will be captured. This theory has important policy implications. If socioeconomic advantage over the life course is associated with better health and quality of life in a dose-response manner, it suggests interventions need to be spread across the whole life course rather than targeted at a particular stage of life.

Latent and pathway effects

In contrast, early experiences are thought to be central to later outcomes under latent and pathway models. Childhood socioeconomic disadvantage has been shown to be associated with a number of adverse health outcomes, independent of current

circumstances (Pollitt et al., 2005; Power & Hertzman, 1997). Therefore, socioeconomic position is said to have a latent (direct) effect on health and wellbeing. Under this model (also often termed the critical period), specific exposures, such as socioeconomic

disadvantage, at sensitive periods in the life course are thought to have a long-lasting effect on later health and wellbeing outcomes (Hertzman et al., 2001). A key example from the health literature is the demonstration that coronary heart disease is influenced by foetal under-nutrition during middle to late gestation (Barker, 1995).

At first, it might seem implausible that a specific exposure during childhood would have a lasting direct effect on quality of life in early old age. However, drawing on the theory of cultural capital (as described above) helps to illuminate why a latent effect might be observed. For example, if the use of books or musical instruments is established early in life, they may have long-lasting direct and indirect effects on quality of life in early old age. As early old age is considered a time for pursuing self-actualisation and pleasure, hobbies which were established earlier in life may become more valued for quality of life during this stage of the life course. In addition, skills and knowledge may have indirect

effects on later quality of life via educational attainment and occupational success, which may contribute to feelings of contentment and satisfaction in early old age. This would therefore point to a pathway mechanism whereby the cultural and related economic resources present early in life have an indirect influence on quality of life via later education and occupation.

To test the latent theory, researchers often examine the association between the early exposure and the later outcome and if the association between the two is still strong and statistically significant after controlling for current circumstances, a latent effect is

suggested (Galobardes et al., 2004; Pollitt et al., 2005). However, if the association is mostly diminished after accounting for current socioeconomic position, this lends support for a pathway effect. Latent and pathway effects can be viewed as complementary. An exposure which exerts a latent effect may not act independently; it may also influence the path which the individual follows across the life course (Power & Hertzman, 1997).

However, separating the two is useful in terms of policy responses. For example, if quality of life in early old age is found to be primarily influenced by current

socioeconomic circumstances, it would suggest that it is not too late to intervene to try to reduce socioeconomic inequalities in quality of life. In contrast, if earlier socioeconomic circumstances are found to influence quality of life directly or indirectly, it suggests interventions early in life may be more effective.

Social mobility

The social mobility theory can also be used to help understand socioeconomic gradients in health and wellbeing in later life. Social mobility refers to the movement between socioeconomic groups, traditionally using measures of social class, over the life course.

Social mobility can be considered analogous to a latent model with subsequent effect modification. In other words, the effect of childhood socioeconomic position on the outcome varies across levels of adulthood socioeconomic position (Mishra et al., 2009).

Social mobility can be separated into inter-generational and intra-generational mobility (Blane et al., 1993). Inter-generational mobility refers to a change in socioeconomic position between generations, often measured by comparing parental occupation to one’s own occupation in adulthood. Intra-generational mobility is the movement

between socioeconomic groups during adulthood, such as the first and last occupations.

No consensus regarding the health consequences of social mobility has been reached.

However, several studies have shown that socially mobile individuals experience levels of health and wellbeing between those of their current class and class of origin, closest to the current social class (Bartley & Plewis, 1997, 2007; Blane et al., 1999b; Claussen et al., 2005). In this respect, social mobility may act to narrow the socioeconomic gradient in health. However, other studies have shown that social mobility may also act to widen the socioeconomic gradient in health if, for example, the health of the downwardly mobile group is worse than that of the people they left behind and those they joined (Boyle et al., 2009; Claussen et al., 2005). In terms of quality of life, it could be hypothesised that if someone experiences a high socioeconomic position during childhood and this guides their future expectations in life, experiencing downward mobility may be associated with a sense of disappointment and negative evaluation of life: a ‘disappointment paradox’

(Osika & Montgomery, 2008).