© 2006 American Public Health Association DOI: 10.2105/AJPH.2005.076158
At the time this research was conducted, Sherman A. James was with the School of Public Health and Institute for Social Research at the University of Michigan, Ann Arbor. Robert F. Belli is with the Department of Psychology at the University of Nebraska, Lincoln. David S. Strogatz is with the School of Public Health at the State University of New York, Albany. John Van Hoewyk, David R. Williams, and Trivellore E. Raghunathan are with the Institute for Social Research at the University of Michigan, Ann Arbor. Correspondence: Requests for reprints should be sent to Sherman A. James, Terry Sanford Institute for Public Policy, Duke University, PO Box 90312, Durham, NC 27708 (e-mail: sjames{at}duke.edu).
Objectives. We investigated the odds of hypertension for Black men in relationship to their socioeconomic position (SEP) in both childhood and adulthood. Methods. On the basis of their parents occupation, we classified 379 men in the Pitt County (North Carolina) Study into low and high childhood SEP. The mens own education, occupation, employment status, and home ownership status were used to classify them into low and high adulthood SEP. Four life-course SEP categories resulted: low childhood/low adulthood, low childhood/high adulthood, high childhood/low adulthood, and high childhood/high adulthood. Results. Low childhood SEP was associated with a 60% greater odds of hypertension, and low adulthood SEP was associated with a 2-fold greater odds of hypertension. Compared with men of high SEP in both childhood and adulthood, the odds of hypertension were 7 times greater for low/low SEP men, 4 times greater for low/high SEP men, and 6 times greater for high/low SEP men. Conclusions. Greater access to material resources in both childhood and adulthood was protective against premature hypertension in this cohort of Black men. Though some parameter estimates were imprecise, study findings are consistent with both pathway and cumulative burden models of hypertension.
Studies documenting an association between low socioeconomic position (SEP) in childhoodor, alternatively, low SEP in both childhood and adulthoodand increased risk for morbidity and mortality from a variety of chronic diseases in adulthood are growing in number.13 A recent review4 focused specifically on life-course socioeconomic factors and risk for cardiovascular disease (CVD) concluded that studies provide moderate support for an independent contribution of low SEP in early life and increased CVD risk factors, CVD morbidity, and CVD mortality in adulthood. Though the review found little support for an independent association between CVD risk and social mobility (i.e., movement from one SEP level in childhood to another in adulthood), fairly consistent support was observed for a positive association between lifelong socioeconomic disadvantage and adverse CVD outcomes in adulthood.4 Three major conceptual models have been advanced5,6 to organize the literature on life-course SEP and early versus late emergence of CVD and other chronic diseases in adulthood. The first is the "latency effects" model,5 also called the "biological chains of risk" model,6 which posits that early-life SEP can influence adult health independent of intervening changes in SEP. The second is the "pathway"5 or "social chains of risk" model,6 which acknowledges the importance of early-life conditions for adult health, but stipulates that important intervening life events (like upward or downward social mobility) can alter health trajectories initiated in early childhood. Finally, the "cumulative burden" model,5 also called the "accumulation of risk" model,6 hypothesizes that health-damaging effects of socioeconomic deprivation in both childhood and adulthood aggregate over the life course to significantly undermine health by middle adulthood. Because of the more widespread availability of epidemiological data on childhood SEP (most commonly measured by fathers occupation) in western and northern Europe, the vast majority of studies dealing with life-course SEP and CVD have been conducted on the European continent.3,4 The number of US-based studies is increasing,3,4 but, to date, these studies have focused largely on White Americans. Indeed, as others4 have noted, the paucity of research on life-course SEP and CVD risk in US racial and ethnic minorities represents a significant gap in the literature. We found only 1 study dealing with life-course SEP and CVD risk in Black Americans. This study,7 which used data from the National Survey of Black Americans, investigated associations between self-reported hypertension and childhood SEP (fathers occupation), adulthood SEP (respondents education and occupation), and downward intergenerational social mobility (i.e., fathers occupation was higher than respondents). Although adulthood SEP was inversely associated with self-reported hypertension, no associations were observed for childhood SEP or downward social mobility. Thus, neither the latency model nor the pathway effects model was supported in this study.7 It is not clear to what extent misclassification of respondents on childhood SEP (and, therefore, downward social mobility) or, alternatively, misclassification on hypertension status (because of reliance on self-report data) biased the findings toward the null in this study. Additional research on life-course SEP and hypertension risk in Black Americans that builds upon this initial effort7 is clearly needed, given the well-documented excess prevalence,810 seriousness,1113 and earlier age of onset8,12 of hypertension in Black Americans. The earlier onset of hypertension in Black adults, relative to Whites, suggests that the origins of the excess risk for this condition among Blacks resides, at least in part, in the problematic social and material life conditions to which numerous Black Americans are exposed in childhood.1416 Using the 3 aforementioned conceptual models5,6 of the relationship between life-course SEP and health in adulthood to frame the research questions, we investigated the contribution of relative socioeconomic deprivationduring childhood, adulthood, and over the life courseto risk for hypertension in a community probability sample of Black men aged 25 to 50 years.
Study Participants Data for this study come from the 2001 follow-up survey of participants in the Pitt County (North Carolina) Study, a community-based, prospective investigation of risk factors for hypertension and related disorders in Blacks aged 25 to 50 years in 1988, the baseline year. Because a major objective of the Pitt County Study was to investigate differential risk for hypertension between working-class and middle-class Blacks, individuals residing in middle-class neighborhoods were oversampled. The baseline sample, the sampling strategy, and the content of the baseline household interview are described elsewhere.17,18 Of the 2225 race- and age-eligible individuals, 1773 (661 men and 1112 women), or 80%, were interviewed in 1988. In 2001, the cohort was reinterviewed to obtain information on the individuals social and economic resources from early childhood to the date of the interview. The goal was to link this life-course information on socioeconomic resources to major CVD risk factors, such as hypertension, obesity,19 type-2 diabetes, and cigarette smoking, as recorded in 1988.
Interviews in 2001 were sought with all cohort members believed to be alive, noninstitutionalized, and residing within a 100-mile radius of Greenville, the countys principal city. Of the 1540 individuals (543 men and 997 women) meeting these criteria, 1221 (428 men and 793 women), or 79%, were reinterviewed. Of these, 43 were excluded because of significant discrepancies in birth year (
Measurement of Blood Pressure
Measurement of Childhood SEP The above 9 categories were subsequently collapsed into 2 broad job categories: skilled (codes 15) versus semi-unskilled (codes 68) or farm laborer (code 9), and designated high and low childhood SEP, respectively. Childhood SEP could not be determined for 21 men because 6 were offspring of single (homemaker) mothers, and 15 had missing data on the family breadwinner variable.
Measurement of Adulthood SEP
The first variable, education, had 4 levels: less than high school, high school, some college, and college graduate. The second variable, occupation, was based on 9 Hollingshead job prestige24 scores: 1=farm laborer/menial service worker, 2=unskilled worker, 3=machine operator or semiskilled worker, 4=skilled manual worker, 5=clerical/sales worker, 6=skilled technician/small business owner, 7=manager/farm owner ( Scores for the adulthood SEP index were produced with the following algorithm: education (less than high school = 0, high-school graduate but less than college = 0.5, college graduate = 1.0), occupation (blue collar = 0, white collar = 1), currently employed (no = 0, yes = 1), and home owner (no = 0, yes = 1). Thus, the highest possible score on the adulthood SEP index was 4.0. To identify individuals who could be plausibly designated as "socioeconomically advantaged," at least relative to other cohort members, persons scoring 3.0 or higher on the adult SEP index were categorized as "high"; those scoring less than 3.0 were categorized as "low."
Measurement of Life-Course SEP
Covariates
Descriptive Variables
Statistical Analysis Hierarchical regression models were used to add potential confounders individually or as a block to isolate their unique contributions to the odds for hypertension. For example, when testing main effects for childhood or adulthood SEP, and similarly when testing additive effects for life-course SEP, the fully adjusted model controlled for potential confounders in the following order: age (model 1); body mass index and waist-to-hip ratio (model 2); smoking, alcohol consumption, and physical exercise (model 3); marital status, instrumental and emotional support, perceived stress, and John Henryism (model 4). For parsimony sake, only the results for models 1 and 4 will be presented. All analyses were performed using SAS, Version 9.12 (SAS Institute Inc, Cary, NC).28 Weighted estimates of parameters, variances, and 95% confidence intervals were obtained using either linearization or Jackknife Repeated Replication techniques.29 Analyses were restricted to the 379 men (70% of the initial target number) with no missing values on study variables.
Table 1
Comparison of baseline demographic and behavioral characteristics by life-course SEP showed statistically significant differences only for age and marital status: High/low SEP men were youngest and least likely to be married whereas low/high SEP men were oldest and most likely to be married. Comparisons involving the 3 variables believed to reflect exposure to childhood material deprivation generally supported the validity of the life-course SEP categories. First, there was a tendency (P<.09) for men from slightly more advantaged childhood backgrounds (high/high and high/low SEP groups) to have grown up in homes with electricity. These men were also more likely (P<.04) to have grown up in homes with indoor plumbing. Interestingly, men in the low/low SEP group had a significantly (P < .01) shorter mean leg length (about 1 inch shorter) than men in the other 3 groups. Furthermore, when mean leg length was compared for men in the low versus high childhood SEP groups, ignoring adulthood SEP, the 372 men in the former group had a significantly (P<.05) shorter mean leg length (37.05 inches) than the 72 men in the latter group (37.90 inches) (data not shown).
The unadjusted, category-specific prevalence of hypertension is shown in Table 2
Table 3
Study findings also pointed to potential pathway effects as indicated, for example, by a nearly 4-fold greater odds (multivariable adjusted OR=3.85; 95% CI=0.91, 16.13) of hypertension among low/high SEP men compared with high/high SEP men. Though sizeable, this odds ratio was actually 47% lower than the odds ratio of 7.27 observed for low/low SEP men, suggesting the potential importance of substantial upward social mobility in mitigating risk for hypertension among Black men who grew up poor. Potential pathway effects are similarly suggested by the multivariable adjusted odds ratio of 5.87 (95% CI=1.25, 27.49) observed for men in the high/low SEP group. Despite having presumably comparable childhood material life conditions, as adults, the high/low SEP men had a 6-fold greater odds of hypertension than their high/high SEP counterparts. Parameter estimates for both pathway models were imprecise, however, because of small sample sizes.
Our study findings indicate that socioeconomic conditions in childhood and adulthood, separately and in combination, influenced the hypertension status of Black men aged 25 to 50 years at the time of their enrollment, in 1988, in the Pitt County Study. The somewhat modest (and nonstatistically significant) 60% excess odds for hypertension associated with low childhood SEP was nevertheless in the direction predicted by the latency effects model.5,6 This study provided stronger support for the cumulative burden model, as evidenced by the 7-fold greater odds of hypertension among men who were relatively disadvantaged in both childhood and adulthood compared with men who were relatively advantaged at both time points. Formal tests of the cumulative burden model, with a specific focus on CVD risk factors, such as hypertension, are still few.4 Our positive findings for Black men in Pitt County agree with evidence supporting a cumulative burden model of hypertension in British women30 and Scottish men.31 We also found some evidence supporting the pathway model, though relevant associations could not be estimated with precision because of small numbers. Membership in the low/high SEP group, which, in this study, represents substantial upward social mobility, was associated with a 47% reduction in the odds of hypertension compared with men who remained relatively disadvantaged in both childhood and adulthood. Whether this is a solid clue regarding the cardiovascular health benefits of significant upward social mobility for Black men, or a chance finding, is a question for future studies to answer. Similar reservations apply to the highly suggestive 6-fold greater odds of hypertension among men in the high/low SEP group, relative to their high/high SEP counterparts. Strictly speaking, of course, men in the high/low SEP group are not necessarily downwardly mobile as many of these men may have acquired more socioeconomic resources (e.g., more education and better-paying jobs) in adulthood than the adults who raised them. The only thing that can be said with confidence is that although the high/low SEP men and the high/high SEP men may have had comparable material resources in childhood, the former had fewer such resources in adulthood. The only other known study of inter-generational social mobility and hypertension in Black Americans7 found no association between downward social mobility and self-reported hypertension. Our study findings cannot be directly compared with that study,7 however, because of major differences in how the 2 studies defined adulthood SEP. Though most other studies also report weak childhood SEP main effects on CVD risk factors in adulthood,4 our study may have underestimated the association between childhood SEP and hypertension status because of either measurement error or limited variation on the exposure variable. Even if the Event History Calendar2022 succeeded in improving respondents recollection of distant life experiences, including the family breadwinners primary occupation, differences in the material well-being of men from low and high childhood SEP backgrounds in the Pitt County Study population may have been too small to predict larger differences in long-term risk for hypertension. Future studies that include a larger number of Blacks with explicit variation in social class backgrounds will be able to avoid this limitation. Our adulthood SEP index incorporated information on respondents home ownership and current employment status as well as their education and occupation. Although respondent occupation (e.g., manual vs nonmanual job) is the most common measure of adulthood SEP used in life-course health research,3,4,7 some investigators32 used an index that included income, housing, material possessions, and job security. Incorporating this kind of "economic security" information in indices of adulthood SEP for research with Black populations could be especially important because a growing literature3340 indicates that Blacks, even those with college degrees or white-collar jobs, have very little wealth (and therefore little real economic security) as measured by net worth or net financial assets.3539 Hence, measures of adulthood SEP that include easily collected wealth data, such as home ownership (the most common form of wealth owned by Blacks)3739 could minimize misclassification on adulthood SEP, thereby enhancing the studys validity for Blacks. The robust, 2-fold excess odds for hypertension observed for men in the low as opposed to high adulthood SEP category in the current study contrasts with the weaker education (and occupation) main effects on hypertension in our earlier work.17,18 This difference is most likely caused by our use of a more informative measure of adulthood SEP for Blacks in this study. The rather large odds ratios observed for the 3 life-course SEP comparisons were attributable to the unusually low prevalence (10%) of hypertension among men in the high/high SEP group. The prevalence for men in the other 3 groups was comparable to the national average (about 34%) for Black men.8,9 Though replication is clearly called for, this unusually low prevalence of hypertension for men in the high/high SEP group points to the potential importance of stable access to adequate socioeconomic resources across the life course for preventing hypertension in Black men. Limitations of our study include a small sample size, which decreased the precision of some parameter estimates; an overrepresentation of respondents in low SEP categories, a legacy of the historically high poverty rates among Blacks in the Southeastern United States;16,40 and our reliance on retrospective childhood SEP data, which, along with limited variation in the childhood SEP measure, could have produced an underestimate of childhood SEP main effects. Although the 30% nonresponse to the 2001 interview is also a limitation, our analyses were weighted to account for nonresponse; thus, the findings apply to all Black men aged 25 to 50 years residing in Pitt County in 1988. Strengths of our study include the following: It is the first fully integrated4 examination of latency, pathway, and cumulative burden SEP models of hypertension in a US Black population; the observed associations involving life-course SEP and hypertension status were largely unaffected by known correlates17,18,2325 of hypertension in this study population; a computerized Event History Calendar2022 was used to improve respondents recall of distant life experiences; and, finally, the research utility of an adulthood SEP index that addressed fundamental economic security issues for Blacks was demonstrated. More research on life-course SEP and CVD risk in Blacks and other US populations of color is clearly needed.4 However, our success in laying a solid empirical foundation in support of multisectoral interventions to eliminate racial and ethnic inequalities in CVD will likely require the development of research models that are attentive to the unique features of a given groups history and standing in America.
This study was funded by the National Institutes of Health (grant HL 65645).
Human Participant Protection
Peer Reviewed
Contributors Accepted for publication October 31, 2005.
1. Kuh D, Ben Shlomo Y. A Life Course Approach to Chronic Disease Epidemiology. 2nd ed. Oxford, England: Oxford University Press; 2004. 2. Davey Smith G, ed. Health Inequalities: Lifecourse Approaches. Bristol, England: The Policy Press; 2003. 3. Galobardes B, Lynch JW, Davey Smith G. Childhood socioeconomic circumstances and cause-specific mortality in adulthood: systematic review and interpretation. Epidemiol Rev. 2004;26:721. 4. Pollitt RA, Rose KM, Kaufman JS. Evaluating the evidence for models of life course socioeconomic factors and cardiovascular outcomes: a systematic review. BMC Public Health. 2005;5:7. Available at: http://www.biomedcentral.com/1471-2458/5/7.[CrossRef][Medline] 5. Hertzman C, Power C. Health and human development: understandings from life-course research. Dev Neuropsychol. 2003;24:719744.[CrossRef][Web of Science][Medline] 6. Ben-Shlomo Y, Kuh D. A life course approach to chronic disease epidemiology: conceptual models, empirical challenges and interdisciplinary perspectives. Int J Epidemiol. 2002;31:285293. 7. Broman CL. Social mobility and hypertension among blacks. J Behav Med. 1989;12:123134.[CrossRef][Web of Science][Medline] 8. Burt VL, Cutler JA, Higgins M, et al. Trends in the prevalence, awareness, treatment, and control of hypertension in the adult US population. Data from the health examination surveys, 1960 to 1991 [published correction appears in Hypertension. 1996;27:1192]. Hypertension. 1995;26:6069. 9. Hajjar I, Kotchen TA. Trends in prevalence, awareness, treatment, and control of hypertension in the United States, 19882000. JAMA. 2003;290:199206. 10. Cooper R, Rotimi C, Ataman S, McGee D, et al. The prevalence of hypertension in seven populations of west African origin. Am J Public Health. 1997;87:160168. 11. Lopes AA, Hornbuckle K, James SA, Port FK. The joint effects of race and age on the risk of end-stage renal disease attributed to hypertension. Am J Kidney Dis. 1994;24:554560.[Web of Science][Medline] 12. Cooper RS, Liao Y, Rotimi C. Is hypertension more severe among U.S. blacks, or is severe hypertension more common? Ann Epidemiol. 1996;6:173180[CrossRef][Web of Science][Medline] 13. Wong MD, Shapiro MF, Boscardin WJ, Ettner SL. Contribution of major diseases to disparities in mortality. N Engl Med. 2002;347:15851592. 14. Duncan GJ, Hill MS, Hoffman SD. Has childrens poverty become more persistent? Am Soc Rev. 1988; 56:538550. 15. Aber JL, Bennett NG, Conley DC, Li J. The effects of poverty on child health and development. Annu Rev Public Health. 1997;18:463483.[CrossRef][Web of Science][Medline] 16. Proctor BD, Dalaker J. Poverty in the United States: 2002. Washington, DC: US Government Printing Office; 2003. US Census Bureau, Current Population Reports, P60 222. 17. Strogatz DS, James SA, Haines PS, et al. Alcohol consumption and blood pressure in black adults: the Pitt County Study. Am J Epidemiol. 1991;133:442450. 18. James SA, Keenan NL, Strogatz DS, Browning SR, Garrett JM. Socioeconomic status, John Henryism, and blood pressure in black adults: The Pitt County Study. Am J Epidemiol. 1992;135:5967. 19. James SA, Van Howeyk J, Belli RF, Strogatz DS, Williams DR, Raghunathan TE. Life-course socioeconomic position and hypertension in African American men: the Pitt County Study, Am J Public Health. 2006; 96:812817. 20. Freedman D, Thornton A, Camburn D, Alwin D, Young-DeMarco L. The life history calendar: a technique for collecting retrospective data. In: Clogg CC, ed. Sociological Methodology, San Francisco: Jossey-Bass; 1988: 3768. 21. Belli RF. The structure of autobiographical memory and the event history calendar: potential improvements in the quality of retrospective reports in surveys. Memory. 1998;6:383406.[Web of Science][Medline] 22. Belli RF, Shay WL, Stafford FP. Event history calendars and question list surveys: a direct comparison of interviewing methods. Public Opin Q. 2001;65:4574.[Abstract] 23. Strogatz DS, Croft JB, James SA, et al. Social support, stress, and blood pressure in black adults. Epidemiology. 1997;8:482487.[CrossRef][Web of Science][Medline] 24. Ainsworth BE, Keenan NL, Strogatz DS, Garrett JM, James SA. Physical activity and hypertension in black adults: the Pitt County Study. Am J Public Health. 1991; 81:14771479. 25. Croft JB, Strogatz DS, Keenan NL, James SA, Malarcher AM, Garrett JM. The independent effects of obesity and body fat distribution on blood pressure in black adults: the Pitt County Study. Int J Obes Relat Metab Disord. 1993;17:391397.[Web of Science][Medline] 26. Smith GD, Greenwood R, Gunnell D, Sweetnam P, Yarnell J, Elwood P. Leg length, insulin resistance and coronary heart disease risk: the Caerphilly Study. J Epidemiol Community Health. 2001;55:867872. 27. Wadsworth ME, Hardy RJ, Paul AA, Marshall SF, Cole TJ. Leg and trunk length at 43 years in relation to childhood health, diet and family circumstances; Evidence from the 1946 national birth cohort. Int J Epidemiol. 2002;31:383390. 28. Bergland PA. Analysis of complex sample survey data using the SURVEYMEANS and SURVEYREG procedures and macro coding. In: Proceedings of the Twenty-Seventh Annual SAS Users Group International Conference. Cary, NC: SAS Institute Inc; 2002. 29. Kish L, Frankel MR. Inference from complex samples. J Royal Stat Soc. Series B, 1974;36:137. 30. Lawlor DA, Ebrahim S, Davey Smith G. Socioeconomic position in childhood and adulthood and insulin resistance: cross sectional survey using data from British womens heart and health study [published correction appears in BMJ. 2003;326:488]. BMJ. 2002; 325:805807. 31. Smith GD, Hart C, Blane D, Gillis C, Hawthorne V. Lifetime socioeconomic position and mortality: prospective observational study. BMJ. 1997;314:547552. 32. Lynch J, Kaplan GA, Salonen R, Salonen JT. Socioeconomic status and progression of carotid atherosclerosis. Prospective evidence from the Kuopio Ischemic Heart Disease Risk Factor Study. Arterioscler Thromb Vasc Biol. 1997;17:513519. 33. Williams DR, Collins C. US socioeconomic and racial differences in health. Annu Rev Sociol. 1995;21:349386.[CrossRef][Web of Science] 34. Collins SM. Black mobility in white corporations: up the corporate ladder but out on a limb. Soc Problems. 1997;44:5567. 35. Changing America: Indicators of Social and Economic Well-Being by Race and Hispanic Origin. Washington, DC: Council of Economic Advisers for the Presidents Initiative on Race; 1998. 36. Blank RM. An overview of trends in social and economic well-being, by race. In: Smelser NJ, Wilson WJ, Mitchell F, eds. America Becoming: Racial Trends and Their Consequences. Vol I. Washington, DC: National Academy Press; 2001:2139. 37. Davern ME, Fisher PJ. Household Net Worth and Asset Ownership. Washington, DC: US Census Bureau; 1995. Current Population Reports, Household Economic Studies, Series P7071. 38. Oliver ML, Shapiro TM. Black Wealth/White Wealth: A New Perspective on Racial Inequality. New York, NY: Routledge Press; 1995. 39. Shapiro TM. The Hidden Cost of Being African American: How Wealth Perpetuates Inequality. New York, NY: Oxford University Press; 2004. 40. The State of the South: Fifty Years After Brown v. Board of Education. Chapel Hill, NC: MDC, Inc; 2004. This article has been cited by other articles:
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||