Time urgency and risk of non-fatal myocardial infarction

Stephen R Colea,b, Ichiro Kawachib, Simin Liua, J Michael Gazianoa, JoAnn E Mansona,c,d, Julie E Buringa,b,c,d and Charles H Hennekense

a Division of Preventive Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA.
b Department of Health and Social Behavior, Harvard School of Public Health, Boston, MA, USA.
c Department of Ambulatory Care and Prevention, Harvard Medical School, Boston, MA, USA.
d Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA.
e Visiting Professor of Medicine, and Epidemiology and Public Health, University of Miami School of Medicine, USA. Current address: 1415 West Camino Real, Boca Raton, FL 33486.

Reprint requests: Dr SR Cole, Division of Preventive Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, 900 Commonwealth Avenue East, Boston, MA 02215, USA. E-mail: scole{at}rics.bwh.harvard.edu

Abstract

Background Inconsistencies in the literature linking Type A behaviour pattern (TAB) to coronary heart disease (CHD) may be due to differences in the effects of various components of TAB, namely aggressiveness, hostility, ambitiousness, competitive drive, and a chronic sense of time urgency.

Methods We investigated the association between sense of time urgency/impatience and non-fatal myocardial infarction (MI) in a study of 340 cases and an equal number of age-, sex-, and community-matched controls.

Results A dose-response relation was apparent among subjects who rated themselves higher on the four-item time urgency/impatience scale (P-value for trend <0.001), with a matched odds ratio (OR) for non-fatal MI of 4.45 (95% CI : 2.20–8.99) comparing those with the highest rating to those with the lowest. After further adjustment for family history of premature MI, physical activity, body mass index, occupation, cigarette smoking, total caloric intake, per cent calories from saturated fat, alcohol intake, lipid levels, treated hypertension and diabetes, the dose-response relation remained (P-value for trend = 0.015) and the adjusted OR for MI was 3.99 (95% CI : 1.32–12.0) comparing those with the highest rating to those with the lowest.

Conclusion In these data, a sense of time urgency/impatience was associated with a dose-response increase in risk of non-fatal MI, independent of other risk factors. Prospective cohort studies of time urgency/impatience and incident CHD events are needed to confirm or refute these observations from a case-control study.

Keywords Coronary heart disease, non-fatal myocardial infarction, time urgency, impatience, Type A behaviour pattern, case-control study

Accepted 24 May 2000

Data concerning Type A behaviour pattern (TAB) and coronary heart disease (CHD) are inconsistent. Type A behaviour pattern is an amalgamation of several elements, including aggressiveness, hostility, ambitiousness, competitive drive, and a chronic sense of time urgency.1 Some of these, referred to as ‘toxic’ elements, may be associated with risk of CHD, while others may not.2 Thus, simple summary scores for TAB of linear combinations of these various behavioural patterns would predict CHD only in samples where the toxic element(s) are weighted strongly in the summary score. Such a situation could arise using a TAB scale that incorporates a large number of items from the toxic relative to the non-toxic elements. This is a measurement problem where the instrument is recording several constructs instead of a single construct, i.e. lack of unidimensionality.3,4

Much of the literature on TAB has focused on hostility as the toxic component of the behaviour pattern.5 However, an inadequate number of studies have examined the cardiovascular risk associated with other components of the behaviour pattern,6,7 such as time urgency, which is characterized as a persistent preoccupation with time and need to complete tasks in a hurry. Indeed, the gold standard for measurement of TAB is the videotaped clinical examination (VCE),8 which devotes approximately equal emphasis to the measurement of time urgency and free-floating hostility.

We previously reported9 on the relation of both overall TAB and suppressed anger with non-fatal myocardial infarction (MI). It remains unclear, however, whether there is any association between the time urgency/impatience component of TAB and MI, and if so, whether any association is independent of traditional coronary risk factors. Noting that researchers may have prematurely abandoned time urgency as a potentially toxic component of TAB, we sought to determine if time urgency, measured with a self-report questionnaire, is associated with non-fatal MI using data from the Boston Area Health Study.

Methods

Subjects
The Boston Area Health Study was a case-control study of 340 patients with first MI and an equal number of age-, sex-, and community-matched control subjects. Case subjects were selected from admissions to the coronary or intensive care units of six suburban Boston hospitals (Emerson, Framingham Union, Leonard Morse, Mount Auburn, Newton-Wellesley and Waltham) between 1 January 1982 and 31 December 1983. Those eligible for inclusion were white men and women under 76 years old living in the Boston area with no previous history of MI or angina pectoris.

Using hospital records, the diagnosis of MI was confirmed based on clinical history accompanied by rise in creatine kinase enzyme. Permission was sought from each admitting physician, and informed consent was obtained from the patients in the hospital. In short, for each case patient, a control subject of the same sex and age (±5 years) was selected at random from the residents' list of the town in which the patient resided. A detailed description of the control sampling strategy has been previously published.10 Each subject was interviewed in his or her home by one of two trained nurse interviewers approximately 8 weeks after discharge from the hospital.

Of the eligible subjects contacted 84% of the cases discharged alive and 60% of controls were enrolled, yielding 340 case-control pairs.

Assessment of time urgency and impatience
We ascertained a sense of time urgency/impatience using four items from the 10-item Framingham Type A scale. This 10-item scale includes three items related to work strain, two items on competitiveness, one item on bossiness, two items on impatience, and two items related to time pressure or urgency. The first time urgency item was ‘Have you often felt very pressed for time?’ The second time urgency item was ‘Usually feel pressed for time’. We scored a positive response to each item as one point. For the two impatience items, subjects were asked to rate how well the traits ‘eating too quickly’ and ‘getting upset when you have to wait for anything’ described them, using the response options of not at all, somewhat, fairly well and very well. For these two items, we scored a response of ‘very well’ as one point. For each subject, we combined these four items into a summed rating scale, with a range of 0 to 4 points.

Assessment of coronary risk factors
We obtained extensive information on coronary risk factors related specifically to the time before the MI for cases and before the interview for controls, including age (years), body mass index (BMI; weight [kg]/height [m2]), cigarette smoking status (never, former, current [<1 pack/day, 1–<2 packs/day, 2+ packs/ day]), family history of premature MI (defined as positive history of MI before age 60 years in the individual's mother, father, or siblings), history of treatment for hypertension (yes/no) and diabetes mellitus (yes/no). We recorded the ‘usual’ occupation for each subject using Edwards' US census grouping of occupations. White-collar occupations included (1) professionals, (2) proprietors, managers and officials (including farm owners and wholesale and retail dealers), and (3) clerks and kindred workers. Blue-collar occupations included (4) skilled workers and foremen, (5) semiskilled workers, and (6) unskilled workers (farm labourers and other labourers). Additionally, we created a category for homemakers. Total caloric intake, per cent of calories from saturated fat and alcohol intake were determined from a 116-item semiquantitative food frequency questionnaire.11 We estimated energy expenditure (kJ) from physical activity with questions about walking, climbing stairs, and participation in sports or recreational activities.12 We determined lipid levels from fasting venous blood samples using the Lipid Research Clinics methods.13 Fasting blood samples were obtained from a subgroup of the cases approximately 8 weeks after hospital discharge, as well as from a subgroup of controls. Statistical analysis for lipids is restricted to the 235 matched pairs with full lipid profiles.

Statistical analysis
We first examined the distribution of coronary risk factors according to case-control status. For these comparisons, we employed continuity-corrected {chi}2 tests for discrete characteristics (sex, treated hypertension and diabetes, family history of premature MI, cigarette smoking status and occupation type), Wilcoxon rank-sum tests for skewed continuous characteristics (physical activity, alcohol intake, very low density lipoprotein [VLDL] and triglycerides) and t-tests for the normally distributed continuous characteristics (age, BMI, total calories, per cent calories from saturated fat, and the balance of the lipid values). We adjusted lipid values for age and sex before making comparisons.

We then examined the distribution of these characteristics according to level of the time urgency/impatience scale. For these comparisons, we employed the Cochran-Armitage test for trend for discrete characteristics (sex, treated hypertension and diabetes, family history of premature MI, cigarette smoking status and occupation type) and the Mantel-Haenszel non-zero correlation test for continuous characteristics (age, BMI, physical activity, alcohol intake, total calories, per cent calories from saturated fat, and lipid values). We assessed the internal consistency reliability of the four-item time urgency/impatience measure using Cronbach's coefficient alpha.14

To examine the association between our measure of time urgency/impatience and non-fatal MI, we used conditional logistic regression to estimate matched pair odds ratios (OR) and 95% CI.15 We took a log transformation for physical activity, VLDL and triglycerides and categorized alcohol intake into quintiles to adjust for the skew in each of these covariates when controlling for them in the multivariable models. Next, we fit a series of models adjusting for each covariate to assess potential confounding or mediating effects, and a full model adjusting for all covariates.

In a secondary set of analyses, we explored the association of time urgency/impatience with non-fatal MI beyond the effects of other components of TAB. To do so, we adjusted the association between time urgency/impatience and non-fatal MI for the six remaining items from the Framingham Type A scale.

Results

Of the 680 subjects, 380 (56%) indicated yes to the item ‘often feel very pressed for time.’ Of the 679 subjects who responded to the remaining three items, 469 (69%) indicated that they ‘usually feel pressed for time,’ 194 (29%) responded that ‘eat too quickly’ described them ‘very well’, and 201 (30%) responded that ‘get upset when you have to wait for anything’ described them ‘very well’. The four time urgency/impatience items combined to provide a scale with a median of 2 (mean = 1.81; quartiles 1,3; range 0–4) and an internal consistency reliability of 0.50.

As expected, the distribution of traditional coronary risk factors among cases differed from controls (Table 1Go). In Table 2Go, a stronger sense of time urgency/impatience was clearly associated with younger age (P-value < 0.001), male gender (P-value = 0.003), higher levels of smoking (P-value < 0.001), white-collar occupation (P-value < 0.001), higher levels of physical activity (P-value = 0.047), and higher caloric (P-value < 0.001) and saturated fat (P-value = 0.013) intake.


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Table 1 Characteristics of cases and controls, Boston Area Health Study 1982–1983
 

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Table 2 Risk factors by time urgency/impatience, Boston Area Health Study 1982–1983
 
In crude matched-pair analysis, the measure of time urgency/ impatience was associated with a dose-response increase in risk of non-fatal MI (P-value for linear trend <0.001; Table 3Go, Figure 1Go). The OR for non-fatal MI among those with the highest rating of time urgency/impatience was 4.45 (95% CI : 2.20–8.99) compared to those with the lowest rating of time urgency/impatience.


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Table 3 Odds ratios for non-fatal myocardial infarction, according to sense of time urgency/impatience, Boston Area Health Study 1982–1983
 


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Figure 1 Age- and sex- and multivariable-adjusted odds ratios for non-fatal myocardial infarction by level of time urgency, compared to subjects with a time urgency score of zero

 
In multivariable models controlling for age and sex by design and family history of premature MI, physical activity, BMI (continuous), occupation, cigarette smoking, total caloric intake, per cent calories from saturated fat, alcohol intake, lipids, history of treated hypertension and diabetes, the measure of time urgency/impatience remained significantly associated with non-fatal MI (P-value for linear trend = 0.015; Table 3Go, Figure 1Go). The adjusted OR for non-fatal MI among those with the highest rating of time urgency/impatience was 3.99 (95% CI : 1.32–12.0), while the adjusted OR among those with a moderate rating of time urgency/impatience (scale score = 2) was 1.99 (95% CI : 0.83–4.82), both compared to those with the lowest rating of time urgency/impatience.

As smoking is the strongest potential confounder, we limited our study to the 193 subjects with no history of smoking and conducted an unmatched analysis. While results are much less precise due to the reduction in sample size, time urgency/ impatience remained associated with risk of non-fatal MI (OR comparing highest time urgency/impatience level to lowest = 2.03, 95% CI : 0.61–6.79).

When we looked at each time urgency/impatience item individually, the matched pair OR were 1.43 (95% CI : 1.02–2.00) for ‘often feel very pressed for time at work,’ 1.67 (95% CI : 1.22– 2.28) for ‘usually feel pressed for time,’ 1.90 (95% CI : 1.34– 2.69) for ‘get upset when you have to wait for anything,’ and 1.36 (95% CI : 0.98–1.89) for ‘eat too quickly.’ Therefore all four items contributed to the association between the summary scale and increased risk of non-fatal MI.

Finally, we adjusted for the six Framingham Type A items which measured other components of TAB (work strain, competitiveness, and bossiness). In this model, time urgency/ impatience remained independently associated with non-fatal MI (P-value for linear trend = 0.001). Here, the TAB-adjusted OR for non-fatal MI among those with the highest rating of time urgency/impatience was 4.00 (95% CI : 1.83–8.75), while the TAB-adjusted OR among those with moderate ratings of time urgency/impatience were also elevated compared to those with the lowest rating of time urgency/impatience (TAB-adjusted OR for scale score of 3 = 1.56 [95% CI : 0.85–2.87], TAB-adjusted OR for scale score of 2 = 1.23 [95% CI : 0.74–2.03]).

Discussion

These data indicate that individuals reporting a greater sense of time urgency/impatience have an increased risk of non-fatal MI. This association was independent of age, sex, family history of premature MI, physical activity, BMI, occupation, cigarette smoking, total caloric intake, per cent calories from saturated fat, alcohol intake, treated hypertension and diabetes, and lipid levels.

The assessment of hostility includes some aspects of time urgency (e.g. ‘It makes me angry to have people hurry me’). However, time urgency may also be related to other psychological characteristics, such as anxiety. For example, approaches to assess anxiety commonly contain a time urgency component, such as ‘I work under a great deal of tension’ or ‘I am not feeling much pressure or stress these days’. Anxiety16,17 and cognitive responses to anxiety, such as worry,18 have been implicated as risk factors for CHD. Our hypothesis that time urgency would prove a particularly ‘toxic’ element of TAB was based upon the evidence relating anxiety to CHD and the observation that time urgency and anxiety are closely related concepts. In the present study, the association between time urgency and non-fatal MI appeared to be independent of the remaining components of TAB, suggesting that time urgency is indeed an independent predictor of increased risk of non-fatal MI.

This case-control study is subject to several limitations. First, as with any case-control study of psychosocial exposures, time urgency and impatience may be differentially recalled among cases and controls. There are several reasons why recall bias is an unlikely explanation for our findings. First, cases were unaware of our hypothesis, and our extensive questionnaire on lifestyle factors was presented to them as a study of factors involved in hospitalization. Second, the time urgency hypothesis is now, and was then (in 1982–1983), not widely known to the lay public. Finally, the primary research question for this case-control study, which concerned alcohol intake and MI, was widely suspected as a factor influencing MI and no recall bias was apparent in this association.19 A definitive test of the hypothesis ruling out recall bias requires prospective measurement of time urgency/impatience. A further limitation of our study is that our results only apply to non-fatal MI. While selecting only non-fatal MI cases limits generalizability, it allowed us to ascertain measures of time urgency and impatience as well as extensive information on coronary risk factors directly from the subjects, making this study possible and reducing the possibility of confounding by unmeasured factors. Third, it is possible that a survivorship bias is at play, whereby fatal MI cases would have demonstrated lower time urgency than the non-fatal MI cases that we observed. Analysis of prospective data will be necessary to rule out this potential, but unlikely, explanation. Fourth, there may be residual confounding by measured factors. However, it is unlikely that there exists any residual positive confounding of measured factors strong enough to cancel the observed association. Fifth, random misclassification of time urgency/impatience may have occurred. Indeed, we provide only marginal evidence of the reliability of our measurement scale, with an internal consistency reliability estimate of 0.50. However, the effect of any random misclassification would tend to diminish the observed association towards the null. Finally, while information on Q-wave infarction would have been desirable, this information was not available.

We previously reported9 that the unadjusted association between overall TAB score and non-fatal MI (matched OR = 1.57; 95% CI : 1.12–2.20) observed in the Boston Area Health Study attenuated markedly after control for high density lipoprotein (HDL) lipid levels (adjusted OR = 1.12; 95% CI : 0.66– 1.90), suggesting either confounding or a pathway through which TAB might affect CHD. However, our present findings indicate that lipid levels did not mediate the association of the time urgency/impatience component of TAB pattern on risk of non-fatal MI. This differing result for the time urgency/impatience component of TAB reinforces the notion that TAB is an amalgamation of disparate elements, for which simple summary scales are problematic.3,4

In 1966, Brozek, et al.20 demonstrated an increased risk of CHD among those reporting the propensity to speak, walk, write, drive, work, and eat quickly even when they did not have to do so. De Backer et al.21 reported a nearly twofold increase in 5-year CHD incidence among those in the highest tertile of the Jenkins Activity Survey subscale S, which measures time urgency, speed and impatience. However, in the VA Normative Aging Study, the Jenkins Activity Survey subscale S was not associated with CHD risk (adjusted RR = 0.86; 95% CI : 0.69–1.09), even though an association was found between Minnesota Multiphasic Personality Inventory (MMPI)-Type A score and CHD.22 Booth-Kewley and Friedman23 reported results from a meta-analysis of time urgency, speed and impatience and various disease endpoints. Among the nine studies of combined CHD outcomes (i.e. including angina) they observed a significant positive association with time urgency (P-value < 0.01), however this finding was attenuated and not significant in the four studies of time urgency and MI (P-value = 0.31). More recently, Powell et al.24 reported an association between time urgency and mortality among 83 non-smoking, non-diabetic women aged 30–63, 6 months after an acute MI. Six deaths occurred during an average of 8.5 years of follow-up, with time urgency associated with a near threefold increase in risk of mortality (RR = 2.86, P-value = 0.02).

Time urgency/impatience may affect CHD endpoints through one or more pathways, including decreased heart rate variability (HRV) or adverse health behaviours. Decreased HRV has been implicated as a potential pathway through which anxiety,25 psychological stress,26 and depression27 alter the incidence of CHD. However, no data are currently available on the association between time urgency and HRV. Alternatively, people with a persistent sense of time urgency/impatience may consequently exhibit other health behaviours that place them at greater risk for CHD. For example, people reporting an increased sense of time urgency/impatience may subsequently exhibit reduced physical activity, poor dietary habits, increased alcohol intake and more smoking. However, our data do not suggest that present smoking status, alcohol intake or physical activity substantially mediate the association between time urgency/impatience and non-fatal MI, as adjustment for these health behaviours did not appreciably attenuate the observed association.

In summary, our data demonstrate a significant increased risk of non-fatal MI associated with time urgency/impatience. Additionally, the risk of MI among those who have an increased sense of time urgency/impatience is independent of traditional coronary risk factors, and appears to be independent of other components of TAB. It is also unlikely that this association is substantially mediated by health behaviours, such as smoking, physical activity, caloric intake and alcohol intake, or by lipid levels. Similar analysis in prospective cohort studies of time urgency/impatience and incident CHD events, which are not subject to recall bias, are needed to confirm or refute these observations.

Acknowledgments

This study was supported by research grants HL-24423 and HL-21006 from the National Heart, Lung, and Blood Institute. The authors thank the six Boston area hospitals that participated in this study: Emerson Hospital (Dr Marvin H Kendrick), Framingham Union Hospital (Dr Marvin Adner and Dr Gerald Evans), Leonard Morse Hospital (Dr L Frederick Kaplan), Mount Auburn Hospital (Dr Leonard Zir), Newton-Wellesley Hospital (Dr James Sidd), and Waltham-Weston Hospital (Dr Solomon Gabbay). Dr Kawachi is supported by a Career Development Award from the National Heart, Lung, and Blood Institute.

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