John Henryism and Cardiovascular Health


Hypertension has long been known to be an important risk factor for cardiovascular diseases (CVDs). Although hypertension is a health problem that affects all ethnic groups, hypertension has been shown to be particularly prevalent in African-Americans. Blacks in the U.S. are 2-4 times more likely than whites in the U.S. to develop hypertension by age 50 (Roberts and Rowland,1981). The reasons for the excess risk in African-Americans are not known. Numerous genetic and environmental factors have been hypothesized to contribute to the excess risk, but their relative contributions are still a matter of debate (Saunders, 1991). However, one thing is clear and universally accepted: socioeconomic status (whether measures are by education, occupation, or income) and hypertension tend to be inversely associated, for both Blacks and Whites (Tyroler, 1986). This has led to the suggestion that unrelieved psychosocial stress, generated by environments in which African-Americans live and work, is primarily responsible for their heightened susceptibility to hypertension.

In the early/mid 1970's, numerous studies demonstrated that "high effort" coping (i.e., sustained cognitive and emotional engagement) with difficult psychological stressors produce substantial increases in heart rate and systolic blood pressure. Increases were shown to persist only as long as individuals actively worked at trying to eliminate the stressor. The effects were seen in a variety of different environments. Some of these studies were controlled laboratory experiments (Obrist et al., 1978), while others were field-based studies of "real life" stressors (Kasl and Cobb, 1970; Cobb and Rose, 1973; Harburg et al., 1973). This body of research led to a commentary by Syme (1979). Syme observed that persons of lower socioeconomic status (especially Blacks in these positions) by definition face more difficult psychosocial environmental stressors than more economically privileged individuals. He proposed that prolonged, high effort coping with difficult psychosocial stressors could be the explanation of both the inverse association between socioeconomic status and hypertension typically observed in U.S. communities and the increased risk for this disorder in Black Americans. This was the beginning of what later became known as the "John Henryism Hypothesis."

What is the John Henryism Hypothesis and how is it assessed?

The term "John Henryism" was coined by Sherman James et al., 1983 as a synonym for prolonged, high-effort coping with difficult psychological stressors. The "John Henryism hypothesis" is the belief that John Henryism (JH) among lower socioeconomic groups that may not have the resources to successively cope with difficult psychological stressors are primarily responsible for the increased prevalence of hypertension among lower socioeconomic groups. James et al., 1983 also provided a 12 item scale called "The John Henryism Scale for Active Coping," or the JHAC12, for measurement of John Henryism. Here are a few examples of the items on the JHAC12:

"I don't let my personal feelings get in the way of doing a job.""Once I make up my mind to do something, I stay with it until the job is completely done."

"Sometimes I feel that if anything is going to be done right, I have to do it myself."

Subjects taking the JHAC12 respond to these items by selecting from the following responses:

1)completely false 2)somewhat false 3)somewhat true 4)completely true 5)don't know

The JHAC12 is still currently the standard measurement of JH.

Research investigating the John Henryism Hypothesis

James et al., 1983, was also the first formal study of the John Henryism hypothesis. 132 randomly-selected, working-class Black men, ages 17-60, from a rural North Carolina community were given the original version of JHAC12 and had their blood pressure measured. This area of the country (Edgecombe county) has among the highest death rates in the country due to stroke and heart disease. Socioeconomic status(SES) was measured by years of formal education. High school graduates were classified as high SES, while high school dropouts were classified as low SES. Consistent with most other published studies, non-high school graduates in this study had higher adjusted diastolic blood pressures than high school graduates(81.1 mm Hg versus 77.1 mm Hg). When divided into high and low John Henryism groups, the difference in mean blood pressure for high school graduates versus non-graduates in the low John Henryism group was very small (1.7 mmHg). Furthermore, as predicted by the John Henryism hypothesis, the difference in mean blood pressure for high school graduates versus non-graduates in the high John Henryism group was considerably larger (6.3 mmHg).

The 1983 by James was largely a pilot study to test the validity of the JHAC12. The positive findings led to a larger study in 1987, again by Sherman James, that consisted of a larger randomly-selected sample that included both Blacks and Whites, ages 21-50, from the same North Carolina rural community. The sample of Whites largely consisted of skilled, blue-collar and lower mid-level white collar workers, while the sample of Blacks consisted mostly of unskilled and semi-skilled workers. Although null findings were found in Whites, the results again showed strong support of the John Henryism hypothesis in Blacks. Among Blacks, the low SES group had a higher mean diastolic blood pressure than the high SES group. More importantly, among Blacks, the difference in mean blood pressure between the high SES group and the low SES group was greater in the high John Henryism group (3.8 mmHg) versus the low John Henryism group (1 mmHg).

Even more striking was the difference in hypertension prevalence between the high SES group and the low SES group when again first divided into high JH and low JH groups. In the low JH group, differences in SES were not associated with drastic differences in hypertension prevalence (25% vs. 23.4%). However, in the high JH group, hypertension prevalence was almost three times greater for Blacks in the low SES group (31.4%) versus those in the high SES group (11.4%). According to James et al.,1987, the 11.5% hypertension prevalence in the high JH/high SES group is unusually low for any group of adult Blacks, and suggests that high JH/high SES might be protective against hypertension for Black adults.

The next major study investigating the John Henryism hypothesis sought to replicate James' previous findings in a totally different population group. Both studies by James et al. previously discussed were confined to the community of Edgecombe County in North Carolina, making generalizations regarding the John Henryism hypothesis outside of the rural South in the United States difficult. Duijkers et al., 1988, studied the relationship between JH, SES, and blood pressure in the Dutch town of Zutphen. Of the 100 men and 100 women randomly selected participants in the study, all were between the ages 20-59 and 96% were Caucasian. As usual, John Henryism was measured using the JHAC12, shown to have high levels of internal consistency by James et al. in their U.S.-based studies. Years of education was used as an approximation of SES. Unfortunately, results for the most part were not statistically significant. After adjustment for age, alcohol consumption, physical activity, and Quetelet Index (a dependent of SES), a statistically significant positive correlation (F(1,92) = 8.04, p<.01) remained only between John Henryism and systolic blood pressure in men. When years of education was also taken into account, the only statistically significant difference (p<.05) in systolic blood pressure observed was in the group with fewer years of education. In this group, those with low JH had a mean systolic blood pressure of 124.6, while those with high JH had a mean systolic blood pressure of 134.9 (after adjustments for the other hypertension risk factors). Comparatively, in the group with greater years of education, the difference between low JH and high JH mean systolic blood pressure was 6.1 mmHg. Similar differences in the sample of 100 women were also found, but due to sample size problems when dividing into subgroups, any generalizations of the John Henryism hypothesis to women became impossible. The results of this study are support that the potential contribution of John Henryism to explaining variance in blood pressure in men is not limited to blacks in the rural South of the United States.

Other studies have attempted to replicate James' findings in study populations that differ not only geographically, but also in age range and/or educational level. Jackson and Campbell, 1994 examined the relationship between John Henryism and blood pressure in 162 male and 259 female black college students from the University of Pittsburgh (Pittsburgh, PA), University of Massachusetts (Amherst, MA), and Paine and Augusta Colleges (Augusta, GA). In this study, no association was found between John Henryism and blood pressure measures. This failure to reproduce the finding of earlier papers has been explained by Jackson and Campbell, 1994 to be likely due to the diversity between this study population and previous ones. John Henryism has almost exclusively been examined in rural, low-SES male populations (Jackson and Campbell, 1994). Their results suggest that John Henryism may not be a significant factor for elevated blood pressure in groups with access to certain economic and social resources, such as those that are college educated. In other words, John Henryism may be a moderator variable between hypertension and other unknown variables that were not present in the study population of Jackson and Campbell, 1994. Another possibility is that the effect of stress beyond the college experience is important in the John Henryism-blood pressure relationship. Longitudinal studies of a similar population of Blacks would be need to test this hypothesis. Whatever the reason for the null findings, it has little relevance to the John Henryism hypothesis, because the study population was not subdivided into groups that differed in their SES. The John Henryism hypothesis predicts that only in low SES groups will John Henryism be positively correlated with blood pressure. It is extremely unlikely that all the study participants were from low SES backgrounds, and so therefore this study does not undermine the John Henryism hypothesis. This study further suggests that John Henryism is a moderator variable and that other additional variables must be taken into account to understand the relationship between John Henryism and blood pressure levels. There is substantial evidence that SES is one of these additional variables, but others may need to be unmasked before relationships become clear.

Although Wilst and Jackson did not find an association between John Henryism and blood pressure in their Black college student study population, there is evidence suggesting that the John Henryism hypothesis is valid in youth, as well as among adults. Wright et al., 1996 have found that high JH scores were associated with higher blood pressure, higher total peripheral resistance (TPR), and lower cardiac output (CO) in their study of 173 normotensive 10- to 17-year-old Black and White children. Consistent with expectations from the John Henryism hypothesis, those children from lower SES backgrounds who were high on John Henryism had particularly high levels of resting cardiovascular reactivity.

However, there have been studies whose null findings have shed doubt on the John Henryism hypothesis. Wilst and Flack, 1992, found no association between an interaction of John Henryism and SES and the risk of elevated blood pressure or definite hypertension. Identical methods to that of James were used in classifying SES and measuring JH. Wilst and Flack, 1992 identified research design and sample characteristics that may have been responsible for their null findings regarding the John Henryism hypothesis. They have proposed that psychological strategies to cope with environmental stressors among southwest urban African-Americans, Wilst and Flack's study population, may differ from those of the rural southeast African-Americans studied by James and colleagues. Additionally, James studied a "relatively poor" community with a low level of education and a high unemployment rate (James et al., 1983), while Wilst and Flack's study population was better educated and had only one-half the unemployment rate. Wilst and Flack identified many other differences in their study population in comparison to James' that may also have contributed to the lack of association, but conclude that more studies of the John Henryism hypothesis in geographically diverse areas are needed to resolve the conflict of their results with that of James' findings.

James and colleagues most recent study also supports the idea that the John Henryism hypothesis does not apply to all African-American population groups. In James' third study (James et al., 1992), 1,784 black adults aged 25-50 years were randomly selected from inhabitants of Pitt County, North Carolina. This study population differed from James' previous studies in Edgecombe County in that Pitt County has experienced more rapid urbanization and economic diversification than Edgecombe County. As a result, many more professional, middle-class Blacks were included in this study, which allowed for the creation of low SES, medium SES, and high SES classification groups. Defying James' predictions, only a very modest and nonstatistically significant inverse association between SES and hypertension prevalence was observed. Furthermore, division of the sample into high and low John Henryism produced data that showed no support for the John Henryism hypothesis. However, upon reanalysis, an additional factor was discovered that James believed was responsible for the lack of an inverse association between SES and hypertension prevalence. Self-reported psychological stress was significantly (p<.05) positively correlated with mean blood pressures for both men and women in the Pitt County study (James et al., 1992). This self-reported psychological stress was noticed to be quite high among managerial level, white collar workers, and presumably raised the prevalence of hypertension to a surprisingly high level for the high SES group as a whole. To test this hypothesis, James and colleagues conducted a pot hoc analysis of the John Henryism hypothesis. They excluded all high SES persons whose psychological stress scores were above the sample median. Additionally, they excluded all low SES persons whose stress scores were below the sample median. With these exclusions, a strong inverse association between SES and psychological stress was observed for the remaining 1,131 participants of the study. These exclusions also had a significant effect on the inverse association between SES and hypertension prevalence: 24.7%, 23.4%, and 17.4% for the low, medium, and high SES groups, respectively. Most importantly, when subdivided into high and low JH groups, it was found hypertension prevalence varied little by SES in the low JH group while a strong, inverse association between SES and hypertension prevalence existed among the high JH group. This has led to the argument that the John Henryism hypothesis might only be observed in the following case:

It is only when chronic psychological stress is higher among lower SES groups than among groups of higher SES (the usual case) that the inverse association between SES and blood pressure will be strong, allowing data supporting the John Henryism hypothesis to be observed. However, the John Henryism hypothesis has not been sufficiently tested under these specific conditions, and so support for the John Henryism hypothesis remains fairly weak. Another important point that also drastically weakens support of the John Henryism hypothesis is that all studies have been cross-sectional. To provide more convincing evidence for the validity of the John Henryism hypothesis, prospective studies must be done that show the combination of low SES and high JH scores at one point in time contributes to an accelerated increase in blood pressure by some well defined, second point in time.

John Henryism and Job Strain

If indeed the inverse relationship between SES and blood pressure strongly depends on chronic psychological stress being more prevalent in lower SES groups, this would further implicate psychological stress as a risk factor for hypertension. Interestingly, high "job strain," a major source of chronic psychological stress, has already been shown to be more strongly associated with hypertension and cardiovascular disease among men with lower SES than with men of higher SES (Johnson and Hall, 1988; Johnson et al., 1989; Karasek, 1981; Theorell et al., 1988). Furthermore, the association between high job strain and high blood pressure is about twice as strong among men with only 14 yrs or less of education vs. those with greater education (Landsbergis et al., 1994). "Job strain" has been defined by Karasek (1979) as work in jobs with high psychological demands (work pace + conflicting demands) and low decision latitude (control + variety and skill use). Five out of nine studies which have studied the relationship between job strain and ambulatory blood pressure found significant positive correlations, while the remaining four yielded a mixture of insignificantly positive and null results (Schnall et al.,1994). Not included in the review by Schnall et al., 1994 was Landsbergis et al.'s 1994 study. Landsbergis et al., 1994 found employees experiencing job strain had a systolic BP that was 6.7 mm Hg higher and a diastolic blood pressure that was 2.7 mm Hg higher at work than other employees, and that the odds of hypertension were also increased (odds ratio = 2.9, 95% CI). According to Schnall et al., 1994, the results taken as a whole, suggest that job strain acts, in part, to cause cardiovascular disease through the mechanism of elevated blood pressure. The link between job strain and hypertension appears to be even stronger than the link between John Henryism and hypertension. Yet although occupational

stress studies have implicated both John Henryism and job strain as likely risk factors for the development of hypertension, there is a major weakness in the literature in regards to whether these two work-stress models are independent or mutually reinforcing risk factors for hypertension and subsequent cardiovascular health problems. Furthermore, it would be interesting to determine whether part of the inconsistencies observed in the literature concerning the relationship between John Henryism and blood pressure could be resolved by taking job strain into account (in a similar way that SES and psychological stress were taken into account in recent John Henryism/hypertension studies).

Social determinants of John Henryism

There has been remarkably little research on the determinants of John Henryism, particularly social class and job stress. Such factors might shape personality development in childhood. For example, certain parental behavior patterns (i.e., overly strict, critical and demanding of conformity) are more common in low SES households, and may be viewed as a reflection of the parents' occupational and other life experiences, which are characterized by low control and insecurity. Similarly, an adult's experience, which might include stressful, low control jobs, may shape their personality development (Kohn and Schooler, 1982)." Thus, research on the social determinants of personality measures believed to be associated with illness outcomes needs to be a major priority in future research.

Conclusions

High JH scores have been associated with elevated blood pressure most reliably among low SES, adult African-Americans. Although less convincingly, this association has also been observed in a wide variety of other sample populations. Positive findings for the association between high JH scores and elevated blood pressure have been found in sample populations that are diverse in sex, age, and ethnicity. The only common thread between the results from these diverse sample populations has been that the high JH/elevated blood pressure association has been consistently strongest in the lowest SES groups.

Based on James' 1994 review, the feature most likely responsible for the pronounced effects among these low SES groups is higher chronic psychological stress. Despite some confliction among the results of studies investigating the relationship between John Henryism, SES, and blood pressure, the evidence as a whole supports that the John Henryism hypothesis is valid at least among specific population groups. However, all studies have been cross-sectional. To provide more convincing evidence for the validity of the John Henryism hypothesis, prospective studies must be done that show the combination of low SES and high JH scores at one point in time contributes to an accelerated increase in blood pressure by some well defined, second point in time. Additionally, future studies are needed to try to integrate the John Henryism hypothesis with other work-stress models, such as job strain, that have been linked more strongly with elevated blood pressure and adverse cardiovascular health consequences.

Lastly, very little is known about the determinants of John Henryism. Research on the social determinants of personality measures believed to be associated with illness outcomes needs to be a major priority in future research.


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