fetal development of the respiratory system could lead to greater susceptibility to chronic obstructive respiratory disease (Ben-Shlomo and Kuh, 2002).

Third, early life events may somehow set one on a pathway that results, possibly many years later, in impaired—or enhanced—health (Hertzman, 2004). Such experiences as early schooling may not immediately affect health but may decisively influence one’s eventual level of completed education and foreclose certain career paths, affecting experiences and later behavior in ways that eventually affect health. For instance, nutritional deficiencies related to poverty, even if they have no irreversible health effect, may produce lung function deficiencies that in the long run result in greater susceptibility to infections of the upper respiratory system. Pathways may involve cumulative effects but are not determinate, since health and development are subject to many influences. The plasticity of these relations means that a person’s late-life health status is not certain but depends on numerous contingencies (Rutter, 1996).

EARLY HEALTH DISADVANTAGE

Health in early life differs among racial and ethnic groups. Time trends since 1950 in birthweight and infant mortality—two basic though not necessarily the most appropriate indicators (Barker, 1998)—show consistent differences that favor whites over blacks and American Indians and Alaska Natives. For Asians and Hispanics, the contrasts with whites are less consistent, but they indicate that these minorities fare better with respect to birthweight though not, in the case of Hispanics, infant mortality. Little is known, however, about racial and ethnic differences in exposure to and experience with illnesses in early life.

Do the early life health differences that are known account for some portion of health and mortality differences among racial and ethnic groups at older ages? Although no coherent body of research attempts to assess such influences in comparison with contemporaneous or other explanations of differences, there is important research on the mechanisms by which early life environments may affect later health.

Conditions in utero and during the first year of life modify patterns of brain tissue growth and thereby alter the functioning of one or more neurophysiological centers of hormonal balance and activation. This functioning influences cellular growth, tissue development, and the ultimate physiological status and functioning of key organs, such as the heart, lungs, and kidneys. Ultimately affected are immune status, resilience, frailty, individual choices, and behavior (Hertzman et al., 2002). That early life health status has such long-term effects is demonstrated in some studies (Barker, 1998; BenShlomo and Smith, 1991), though not all (Christensen et al., 1995; Leon, 1995; Vagero and Leon, 1994).



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