Methylmercury: A Case Study

The case of methylmercury as an environmental pollutant illustrates the potentially dramatic effects of the physical environment on health. Environmental toxins are a specific form of environmental hazard, caused in most cases by industrial enterprises, and the adverse effects of such toxins on the nervous system have been well documented. High levels of exposure to certain environmental pollutants are known to cause acute effects including convulsions, paralysis, coma, and death. The effects of lead on health and development have been documented for decades, and policy action regarding leaded gasoline and lead-based paints has been taken, with positive effects on child health. Impact Of Aggregate Living On Population Health Essay.  However, there is growing concern about emerging evidence that other ubiquitous pollutants such as polychlorinated biphenyls (PCBs) and mercury may cause behavioral problems and affect mood and social adjustment. The adverse impacts of exposure to these pollutants may be most profound during fetal development and early childhood. Amidst growing national concern about developmental disabilities, exposure to mercury in the environment represents an emerging and preventable environmental health threat.

The National Research Council (NRC) report Toxicological Effects of Methylmercury (NRC, 2000) examined the evidence of adverse health impacts resulting from exposure to mercury, focusing on consumption of seafood contaminated by releases to the environment. Fossil fuel combustion represents the major source of mercury released to the environment. The deposition of mercury on the land and in surface waters results in conversion to forms that accumulate in the food chain. This bioaccumulation can result in very high concentrations of mercury in some fish, which are the main source of exposure for the population. The developing brain is particularly sensitive to the adverse effects of mercury exposure. Prenatal exposures may interfere with the growth and development of neurons and cause irreversible damage to the nervous system. Infants whose mothers were exposed to high levels in poisoning episodes in Minamata, Japan, and in Iraq were born with severe disabilities, including mental retardation, cerebral palsy, blindness, and deafness (EPA, 1997; NRC, 2000). More recently, epidemiological studies of lower-level exposure from maternal fish consumption have raised concerns about subtle neurodevelopmental deficits. Impact Of Aggregate Living On Population Health Essay.

The NRC report concluded that the evidence of developmental neurotoxic effects from mercury exposure is strong and called for revision of the Environmental Protection Agency (EPA) reference dose that provides public health guidance on acceptable population exposure levels. This conclusion was based on epidemiological studies of low-level chronic exposure from seafood consumption. The population at risk consists of women of childbearing age and their children. Frequent consumers, particularly of fish that tend to accumulate high levels of mercury, may be exposing their unborn children to levels of mercury in the range that has been shown to be associated with developmental deficits. Based upon the available data on fish consumption, the NRC committee estimated that as many as 60,000 newborns may be at risk for adverse neurodevelopmental effects from in utero exposure to mercury. Recently, the Centers for Disease Control and Prevention (CDC) released the first National Exposure Report, which provided dramatic confirmation of the emerging threat of mercury. Ten percent of a national sample of women of childbearing age had mercury levels in their blood within 1/10 of potentially hazardous levels, indicating a narrow margin of safety for many women (CDC, 2001c).

Currently, 40 states have issued fish consumption advisories to reduce exposure to mercury. EPA and the Food and Drug Administration (FDA) have also recently revised their guidance concerning consumption of fish species that have been shown to have high levels of mercury. Ultimately, the threat of mercury can be most effectively reduced through control of the sources of pollution. However, control of sources from the burning of fossil fuels may be decades away. In the meantime, prevention of adverse public health impacts from mercury will require a partnership among health care providers, public health agencies, and others.

The example of methylmercury clearly illustrates the serious impact of just one environmental risk factor. The influences of many other environmental risk factors on health have not been fully documented, and evidence of the influence of environmental factors for some health conditions like asthma is rapidly accumulating (Trust for America’s Health, 2001). Impact Of Aggregate Living On Population Health Essay. The association between certain chronic diseases and environmental causes is devastatingly clear, yet knowledge about the scope of environmental health risks and their impact on the public’s health is limited. Most states do not track environmental risk factors like pesticides and other hazards or most chronic diseases (such as asthma) and birth defects (Pew Environmental Health Commission, 2001). Certainly, a significant amount of work remains to be done to address the physical environment’s powerful influence on health status. A great deal about health determinants in the built and natural environments has been learned in recent decades, but much more is yet to be examined.

Socioeconomic Status and Health

A strong and consistent finding of epidemiological research is that there are health differences among socioeconomic groups. Lower mortality, morbidity, and disability rates among socioeconomically advantaged people have been observed for hundreds of years; and in recent decades, these observations have been replicated using various indicators of socioeconomic status (SES) and multiple disease outcomes (Syme and Berkman, 1976; Kaplan and Keil, 1993). SES is defined in terms of education, income, and occupation. Furthermore, educational differentials in mortality have increased in the United States over the past three decades, leading to a growing inequality, even though mortality rates have dropped for all groups (Feldman et al., 1989; Pappas et al., 1993; Tyroler et al., 1993).

Although it may be measured as level of education or income, SES is a complex phenomenon often based on indicators of relationships to work (occupational position or ranking), social class or status, and access to power. From a policy perspective as well as an etiological perspective, it is important to understand which of the components is critical—for instance, if education is found to be important, the policies that may be implemented would differ from the policies needed if income was found to be the most influential factor. Impact Of Aggregate Living On Population Health Essay. In fact, most research has not tested such competing hypotheses directly, so in the examples that follow, these have not been disaggregated, although the indicators used in each study are explicitly identified.

Several major studies have ascertained that education, income, and occupation, as indicators of SES, are associated with mortality and with mortality due to certain causes. The National Longitudinal Mortality Study found that mortality was strongly associated with all three measures of SES (Rogot et al., 1992; Sorlie et al., 1992, 1995) (see Box 2–1).

The Multiple Risk Factor Intervention Trial followed 320,909 white and African-American men for 16 years (Davey Smith et al., 1996a, 1996b) and found that the median family income in one’s zip code of residence was predictive of death from a variety of causes. Heart disease, the leading cause of death in the United States, provides a strong example of the association between SES and mortality. Research has documented the relationship between SES and cardiovascular disease (NCHS, 1992; Kaplan and Keil, 1993), and the British Whitehall longitudinal study of civil servants found that those in the lowest grades of employment were at the highest risk for heart disease (Marmot et al., 1991).

A striking finding that emerges from analyses of occupation- and area-based income measures is the graded and continuous nature of the association between socioeconomic position and mortality, with differences persisting well into the middle socioeconomic ranges (Davey Smith et al., 1990; Blane et al., 1997; Macintyre et al., 1998). For example, in the Whitehall studies (Davey Smith et al., 1990; Marmot et al., 1991), the individuals in each employment grade had worse health and a higher rate of mortality than those in the grade above.

Although many of the studies that focused on occupation-, education-, or area-level SES showed a gradient that is virtually linear, studies that focus on income often show somewhat different results. For example, in work by Backlund and colleagues (1996), the association between (increasing) income and (decreasing) mortality is clearly curvilinear, with the decline in the mortality rate with increasing income greatest among those in groups earning less than $25,000 per year but with the decline with increasing income being much less among those earning between $25,000 and $60,000 per year. Impact Of Aggregate Living On Population Health Essay.This curvilinear relationship suggests diminishing returns of income as one approaches the highest income categories, although some association may persist. This curvilinear association between income and health is what lays the framework for findings that more egalitarian societies (i.e., those with a less steep differential between the richest and the poorest) have better average health, because a dollar at the bottom “buys” more health than a dollar at the top. Whether SES has a linear or curvilinear relationship with health has enormous implications for understanding both the etiologic associations and the policy implications of this research. In either case, however, it is important to note that a “threshold” model focused exclusively on the very poorest segments and ignoring others near the bottom and the working poor will not address the relatively poor population health outcomes for the U.S. population as a whole. The major reason for this is because there are groups in the moderate-risk categories of working poor and working class who contribute disproportionately large numbers to death rates and poor health outcomes.

SES is linked to health status through multiple pathways (such as distribution of health care, psychosocial condition, toxic physical environments, and health-related behaviors), but these relationships have not yet been fully elucidated. It is also likely that some degree of reverse causation influences the strength of these associations. Studies in which education rather than income or occupation is used as an indicator of SES are stronger in this regard since most people are not influenced by serious chronic diseases related to cardiovascular disease, stroke, or cancer in ways that inhibit their level of educational attainment in their adolescence and early twenties. Furthermore, although many studies have included a broad range of covariates in their multivariable analyses, it is of course possible that unobserved attributes account for some observed disparities. Impact Of Aggregate Living On Population Health Essay. There is ample evidence that SES is strongly related to access to and the quality of preventive care, ambulatory care, and high-technology procedures (Kaplan and Keil, 1993); but health care appears to account for a small percentage of the variation in health status among different SES groups. It has been argued that differential access to health care programs and services is not entirely responsible for socioeconomic differentials in health (Wilkinson, 1996), because causes of death that apparently are not amenable to medical care show socioeconomic gradients similar to those for potentially treatable causes (Mackenbach et al., 1989; Davey Smith et al., 1996a). Furthermore, similar gradients persist in countries with universal coverage, such as the United Kingdom.

Despite the past century’s great advances in sanitation, which have contributed to the sharp increase in life expectancy observed among all socioeconomic groups, the socioeconomic gradient in health status persists. It has been proposed, and to some extent documented, that the gap in health status by SES may still be attributable to the effects of crowded and unsanitary housing, air and water pollution, environmental toxins, an inadequate food supply, poor working conditions, and other such deficits that have historically affected and that still disproportionately affect those in the lower socioeconomic strata (USPHS, 1979; Williams, 1990; Adler et al., 1994; Sargent et al., 1995; McLoyd, 1998). Studies that incorporate assessments of material deprivation and aspects of the physical environment will be important to explicate these important potential pathways.

Considerable evidence links low SES to adverse psychosocial conditions. People in lower socioeconomic positions are not only more materially disadvantaged, but also have higher levels of job and financial insecurity; experience more unemployment, work injuries, lack of control, and other social and environmental stressors; report fewer social supports; and more frequently, have a cynically hostile or fatalistic outlook (Berkman and Syme, 1979; Karasek and Theorell, 1990; Adler et al., 1994; Heaney et al., 1994; Bosma et al., 1997).  Impact Of Aggregate Living On Population Health Essay.

There is most often, especially in the United States, a striking and consistent association between SES and risk-related health behaviors such as cigarette smoking, physical inactivity, a less nutritious diet, and heavy alcohol consumption. This patterned behavioral response has led Link and Phelan (1995) to speak of situations that place people “at risk of risks.” Understanding why “poor people behave poorly” (Lynch et al., 1997) requires recognition that specific behaviors formerly attributed exclusively to individual choice have been found to be influenced by the social context. The social environment influences behavior by shaping norms: enforcing patterns of social control (which can be health promoting or health damaging); providing or denying opportunities to engage in particular behaviors; and reducing or producing stress, for which engaging in specific behaviors (such as smoking) might be an effective short-term coping strategy (Berkman and Kawachi, 2000). Both physical and social environments place constraints on individual choice. Over time, those with more economic and social resources have tended to adopt health-promoting behaviors and reduce risky behaviors at a faster rate than those with fewer economic resources.

Socioeconomic disparities in health in the United States are large, are persistent, and appear to be increasing over recent decades, despite the general improvements in many health outcomes. The most advantaged American men and women experience levels of longevity that are the highest in the world. However, less advantaged groups experience levels of health comparable to those of average men and women in developing nations of Africa and Asia or to Americans about half a century ago (Berkman and Lochner, 2002). Furthermore, these wide disparities coupled with the large numbers of people in these least-advantaged groups contribute to the low overall health ranking of the United States among developed, industrialized nations. Impact Of Aggregate Living On Population Health Essay. A major opportunity for us to improve the health of the U.S. population rests on our capacity to either reduce the numbers of the most disadvantaged men, women, and children in the highest risk categories or to reduce their risks for poor health.

Racial and Ethnic Disparities in Health

A substantial body of research documents the relationship between racial and ethnic disparities and differences in health status. Numerous studies have shown that minority populations may experience burdens of disease and health risk at disproportionate rates because of complex and poorly understood interactions among socioeconomic, psychosocial, behavioral, and health care-related factors (NCHS, 1998; DHHS, 2000; IOM, 2002). Although Americans in general experienced substantial improvements in life expectancy at all ages throughout the twentieth century, substantial gaps in life expectancy, morbidity, and functional status remain between white and minority populations. Life expectancy at birth for African Americans in 1990 was the same as that for whites in 1950. Even after controlling for income, African-American men and women have lower life expectancies than white men and women at every income level (for example, see Geronimus et al. [1996] and Anderson et al. [1997]). When indicators of SES are considered, these differences, which are often substantial across a diversity of health outcomes, are commonly reduced but remain significant. Few studies have adequately controlled for SES in terms of the inclusion of economic indicators of wealth, homeownership, or other sources of income. Although these indicators should be included, they are unlikely to reduce disparities between African Americans and whites because data suggest that there are even greater disparities in wealth (all assets) than in household income between these two groups (Ostrove et al., 1999). This phenomenon has led researchers to investigate the health effects of discrimination itself. Aspects of discrimination might influence health through any number of mechanisms, including SES. However, conceptualizing discrimination (whether it applies to racial or ethnic minorities, women, homosexuals, or groups of different ages) as a stressful experience that can influence disease processes through a number of potential pathways is a major advance in scientific thinking over the past decade (Krieger and Sidney, 1996). Impact Of Aggregate Living On Population Health Essay. Additionally, although many disparities are measured across broad racial and ethnic classifications, there is significant health status differentiation or “hidden heterogeneity” within, for instance, Asian-American and Pacific Islander populations (NCHS, 1998). The acknowledgment of disparities itself may generalize or aggregate groups that are highly heterogeneous because of variations ranging from the date of immigration and level of acculturation to genetic, social, and cultural differences (Williams and Collins, 1995; Korenbrot and Moss, 2000).

African Americans and other minority populations experience worse health from infancy to old age. Although the national infant mortality rate has decreased over the years to about 7 per 1,000, the rate among African-American infants is nearly twice as high, 14 per 1,000, and that among American Indians is 9.3 per 1,000, whereas it is 5.8 per 1,000 among whites (NCHS, 2002).

Rates of illness such as asthma are much higher among African Americans than among whites, as are levels of obesity, diabetes, and other cardiovascular risk factors that are often established in adolescence and young adulthood. For example, the prevalence of obesity among African Americans is 29.3 percent and that among Hispanics is 21.5 percent, whereas it is 18.5 percent among whites (CDC, 2002). In 2000, the rate of diabetes-related mortality in non-Hispanic African Americans was 49.4 (per 100,000), whereas it was 32.4 in Hispanics and 20.8 in non-Hispanic whites (CDC, 2001b). Rates of death due to HIV/AIDS are 31.9 among African Americans and 3.7 among whites (CDC, 2000).

Some of the racial and ethnic differences in health status may be associated with the fact that minority populations often encounter the health care system in very different ways in terms of both access and quality of care (Fiscella et al., 2000). For a variety of reasons—both structural (having to do with the health care system itself) and financial or cultural—racial and ethnic minorities encounter barriers to health care that often result in less than optimal care and worse outcomes (Carlisle et al., 1997; Epstein and Ayanian, 2001; IOM, 2002). For example, many studies have concluded that African-American patients are significantly less likely than white patients to receive certain revascularization procedures to treat coronary artery disease (Epstein and Ayanian, 2001). Barriers to care may include linguistic differences, a lack of insurance or difficulties with payment, immigration status, social issues such as trust and some pervasive but subtle forms of racism and discrimination, and even logistical problems related to distance and transportation (Thomas, 2001; IOM, 2002). African-American and Hispanic children are more likely to be uninsured than white children and are less likely to have a usual source of health care (Weinick and Krauss, 2000). Recent research indicates that disparities in access persist even after controlling for socioeconomic circumstances and health insurance coverage status (Roetzheim et al., 1999; Weinick and Krauss, 2000). Among other disparities in health care, African Americans have been shown to be less likely to receive certain diagnostic testing; adequate pain medication; early-stage diagnoses of cancer; dialysis as initial treatment for end-stage renal disease, placement on a kidney transplant waiting list, or a kidney transplant; and preventive rather than acute asthma control measures (IOM, 2002). Hispanics are also likely to experience similarly unequal access to health care services (IOM, 2002). With regard to treatment for HIV infection, once tested, HIV-infected African Americans are less likely to receive antiretroviral and related therapies (IOM, 2002). This is in the context of the fact that HIV infection is spreading more rapidly among African Americans and Hispanics than among whites.

Although many studies indicate that certain racial differences in health persist among people of similar SES, it is also true that many minority groups are likely to be poorer and more disadvantaged than whites. This overlap along both racial and economic lines creates a kind of “double jeopardy,” which is associated with substantially increasing risks for poor health. In terms of the association between poverty and minority status, in 1998, for instance, 10 percent of non-Hispanic white children lived in poverty, whereas 36.4 percent of African-American children and 33.6 percent of Hispanic children lived in poverty (CDC, 2000). When health outcomes are examined by level of education of the mother, family income, and ethnicity and race, enormous differences emerge between the least-advantaged African-American children and the most advantaged white children. Impact Of Aggregate Living On Population Health Essay. For instance, among African-American children living below the poverty line, 22 percent have elevated blood lead levels, whereas 6 percent of African-American children in high-income families and slightly more than 2 percent of white children in high-income families have elevated blood lead levels. These patterns are persistent and are seen for other outcomes such as low birth weight and hospitalizations for asthma (NCHS, 1998). Such pronounced disparities have led to a presidential initiative targeted at ethnic and racial health disparities in six specific areas (White House, 1998; Office of Minority Health, 2000). Also, the elimination of health disparities is a goal of Healthy People 2010 (DHHS, 2000).

Social Connectedness and Health

The association between social connectedness and health has received much attention in recent years. Concepts of social connectedness relate to social integration at the broadest level, social networks, social support, and loneliness. Social connectedness may be conceptualized as a societal characteristic related to civic trust and social capital. This area-level experience is discussed in a later section. This section reviews the evidence that the structure of social ties is related to health outcomes and discusses pathways that may link such social experiences to health. People form ties to others the moment they are born. The survival of newborns depends upon their attachment to and nurturance by others over an extended period of time (Baumeister and Leary, 1995). The need to belong does not stop in infancy, but rather, affiliation and nurturing social relationships are essential for physical and psychological well-being throughout life.

Over the past 20 years, 13 large prospective cohort studies in the United States, Scandinavia, and Japan have shown that people who are isolated or disconnected from others are at increased risk of dying prematurely from various causes, including heart disease, cerebrovascular disease, cancer, and respiratory and gastrointestinal conditions (Berkman and Syme, 1979; Blazer, 1982; House et al., 1982, 1988; Welin et al., 1985; Schoenbach et al., 1986; Orth-Gomer and Johnson, 1987; Cohen, 1988; Kaplan et al., 1988; Seeman et al., 1988, 1993; Sugisawa et al., 1994; Seeman, 1996; Pennix et al., 1997). Studies of large cohorts of people enrolled in health maintenance organizations or occupational cohorts also report that social integration is critical to survival, although it may not be as critical an influence on the onset of disease (Vogt et al., 1992; Kawachi et al., 1996). Impact Of Aggregate Living On Population Health Essay.

Powerful epidemiological evidence supports the notion that social support, especially intimate ties and the emotional support provided by them, is associated with increased survival and a better prognosis among people with serious cardiovascular disease (Orth-Gomer et al., 1988; Berkman et al., 1992; Case et al., 1992; Williams et al., 1992) and strokes (Friedland and McColl, 1987; Colantonio et al., 1992, 1993; Glass et al., 1993; Morris et al., 1993). The lack of social support, expressed in terms of conflict or loss of intimate ties, is also associated with health outcomes and risk factors such as neuroendocrine changes in women (Kiecolt-Glaser et al., 1997), high blood pressure (Ewart et al., 1991), elevated plasma catecholamine concentrations (Malarkey et al., 1994), and autonomic activation (Levenson et al., 1993). Caregivers of relatives with progressive dementia are characterized by impaired wound healing (Kiecolt-Glaser et al., 1995, 1998). Social conflicts have been shown to increase susceptibility to infection (Cohen et al., 1998).

Several studies have recently shown that older men and women with high levels of social engagement and networks have slower rates of cognitive decline (Bassuk et al., 1999; Fratiglioni et al., 2000) and better survival independent of physical activity (Glass et al., 2000). The pathways by which social networks might influence health are multiple and include pathways related to health behaviors, health care, access to material resources such as jobs, and direct physiological responses leading to disease development and prognosis. For instance, evidence suggests that, in general, social network size or connectedness is inversely related to risk-related behaviors. People who are socially isolated are more likely to engage in such behaviors as tobacco and alcohol consumption, to be physically inactive, and to be overweight (Berkman and Glass, 2000). Behavioral pathways such as these do not appear to account for a large part of the association between social isolation and poor health, but they are important to consider. It is important to note that networks themselves have generally been shown to exert powerful influences on the behavior of both adolescents and adults, so that networks can either promote health or increase risk depending on the norms of the networks themselves.

Experimental work with animals and humans indicates that social isolation can have a direct effect on physiologic function and subsequent diseases. Animals that are isolated in adulthood, that experience maternal separation, or that are not nurtured in infancy develop more atherosclerosis; have poor, inefficient, or exaggerated neuroendocrine responses; and may have higher levels of immunosuppression (Nerem, 1980; Shively et al., 1989; Suomi, 1991; Meaney et al., 1996). Among humans and primates, those who lack affiliation and strong social networks have been shown to be more likely to develop colds, have stronger stress responses in terms of neuroendocrine reactions and higher levels of cardiovascular reactivity, and have altered immune responses (Glaser et al., 1992, 1999; Kirschbaum et al., 1995; Cohen et al., 1997; Sapolsky et al., 1997; Roy et al., 1998; Cacioppo et al., 2000). There is limited research on whether access to material goods and resources is a mechanism through which social networks might influence health, and this is an important area for investigation. Impact Of Aggregate Living On Population Health Essay.  We do know, however, that networks have the capacity to provide informational and instrumental support effectively. Although much of the research in this area examines the effects of close relationships and social support, there is also evidence that weak social ties may also have indirect positive effects on health and well-being. For instance, a classic investigation of how people find jobs suggests that weak ties to others may be more helpful in enabling people to find jobs, providing access to one of the most critical life opportunities. Whereas one’s close friends and relatives (who are likely to belong to the same social circles) may often provide redundant information, weak social ties (e.g., a friend of a friend) may allow individuals to tap into new sets of information (Granovetter, 1995). Instrumental and informational support, two critical components of the support paradigm, relate to help with practical matters such as grocery shopping; rides to the doctor; and information about health care, behavior, and risk. Finally, many of the observational data linking social connectedness to health outcomes do not permit us to rule out issues of reverse causation or the possibility that some unobserved condition explains these associations. More experimental work is needed to answer these questions completely. Much of the experimental work cited here supports the concept that social isolation increases the risk for poor health. However, a recent clinical trial, Enhancing Recovery in Coronary Heart Disease, aimed at improving social support to reduce mortality and reinfarction among subjects after myocardial infarction, found no effect (NIH, 2001). Developing both clinical and population-based experimental studies is the next step in this work.

A large body of evidence accumulated over the last two decades consistently points to the importance of social connectedness, and incorporation of this evidence would involve the inclusion of nurturing community and social networks. As we think of broad social determinants of health that could be influenced to improve health, social connections may be one example that has the support of a number of sectors. Because social relationships influence health through such a myriad of pathways, broad health improvements may be facilitated by considering and enacting policies that support social connections. Impact Of Aggregate Living On Population Health Essay.

Work-Related Conditions and Health

Two decades of research show that the workplace not only generates adverse health effects due to economic circumstances such as downsizing and unemployment or to work conditions such as job demands, control, latitude, and threatened job loss (Karasek and Theorell, 1990), but also generates protective health effects such as social ties that may help counteract the physical and mental adverse effects of work stressors (Buunk and Verhoeven, 1991). The “demand–control” model was developed to describe the psychosocial work environment (Karasek and Theorell, 1990), and other empirical studies have tested the predictive validity of the model with respect to physical health, for instance, by examining the effects of reward relative to effort (Sigerist, 1996).

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It has been hypothesized that job strain (the combination of a psychologically demanding workplace and a low level of job control) leads to adverse health outcomes, and findings show that job control is an important component of health-promoting work environments (Johnson et al., 1996; North et al., 1996; Bosma et al., 1997, 1998; Theorell et al., 1998). Schnall and colleagues (1994) found that lower levels of job control (the opportunity to use and develop skills and to exert authority over workplace decisions) were predictive of adverse cardiovascular disease outcomes in 17 of 25 studies, whereas high psychological demands of work had similarly negative effects in only 8 of 23 studies.

The links between unemployment and health have been investigated by European researchers and, to a somewhat more limited extent, U.S. researchers.  Impact Of Aggregate Living On Population Health Essay.Although longitudinal studies of European populations have demonstrated a significant relationship between unemployment and higher standardized mortality ratios (SMRs), even after adjusting for age and social status (Moser et al., 1984, 1986, 1987; Costa and Segnan, 1987; Iversen et al., 1987; Martikainen, 1990; Kasl and Jones, 2000; Stefansson, 1991), U.S. data based on the U.S. National Longitudinal Mortality Study (Sorlie and Rogot, 1990) have shown no significant association between age, education, and income-adjusted SMRs and unemployment for either men or women. However, other U.S. epidemiological findings associate unemployment or risk of job loss with health conditions such as depression and engagement in negative health behaviors such as substance abuse, poor diet, and inactivity (Dooley et al., 1996). Analysis of panel data from the U.S. Epidemiologic Catchment Area study suggested that the 1-year incidence of clinically significant alcohol abuse was greater among those who had been laid off than among those who had not (Catalano et al., 1993). Examination of cases of job loss due to factory closures is important because worker characteristics in such cases have no effect on the loss of jobs. Morris and Cook (1991) reviewed longitudinal studies of factory closures and found that the job loss experience exerts a negative effect on physical health. Impact Of Aggregate Living On Population Health Essay.