Personality characteristics influencing determinacy of day and night blood pressure and heart rate

Abstract

The evidence of emotional impacts on day and night blood pressure (BP), heart rate (HR) and non‐dipping of BP remains fragmentary. Personality traits previously tested by self‐reports as determinants of office, screening or mean daytime BP produced mixed results. Therefore, we hypothesized that some traits are acting together as modifiers of 24‐h and day/night ambulatory BP and HR. A population sample of healthy 47–54 year‐old men, n = 85, unaware of their BP status, was evaluated. In multiple regression, 25% of the 24‐h systolic BP (SBP) variation was explained by independent augmenting predictors Trait Anger–Anger Expression Styles, Large and Lasting Emotions, and by an attenuating predictor Anxiety. Only Verbal Aggression increased night‐time SBP much more than daytime SBP and diminished day–night dipping of SBP. Strong Large/Lasting Emotions and Indirect Aggression increased daytime SBP only. Day and night HR increased with a high Suspicious Hostility (7.4% of variation), in particular with items Distrust/Vulnerability (11.5% of variation). In conclusion, mean levels of HR and BP during a 24‐h period are slightly modified by particular personality traits. Some traits appear to affect either daytime or night‐time periods more. Day to night carry‐over effects on SBP may occur.

• Anger
• Aggression
• Self‐confidence
• Ambulatory
• Daytime
• Night‐time

Introduction

Our initial working idea relied on concepts of cardiovascular arousals in alerting and defense reactions [1–3] and psychosocial hypertension [4]. We present here the gradual development of the evidence describing the physiological arousals, particular arousing emotions, personality traits and life situations leading to blood pressure (BP) and heart rate (HR) elevations.

Every behavior and reaction is accompanied by a regional, organ‐specific change in hemodynamics. Some of these changes can be related to the pathogenesis of hypertension [2], [3],[5]. In an important report [6], the increasing mental arousal ranging from its lowest level in sleep to its highest level during mental stress was clearly associated with increasing levels of continuously recorded BP. Provoked states of mental stress, anger, hostility and angry frustration caused by harassment were accompanied by cardiovascular arousals with delayed recovery. Also, simply thinking about a stressful experience produced significant and sustained BP responses, which in some cases were as large as the initial response to the stressor [7]. Even personality traits may influence reactivity to stress in young men [8]; here the increased cardiovascular reactivity and the sympathoadrenal activation to stress predicted elevated BP in the distant future [9].

In previous studies of the association between personality and negative emotions with increased BP, the characteristics of subjects, the level of BP, the recruiting of participants and the type of investigations varied; cross‐sectional and prospective studies were performed. In some studies, the participants had previously been treated with antihypertensive drugs or were aware of their BP status. Usually office/screening BP or field daytime ambulatory BP recordings were used. Daytime BP and HR are affected by physical and mental activities; these confound and dilute the possible effects of psychosocial traits. Instead of office or daytime recordings the 24‐h ambulatory recording is preferable for its higher repeatability and for the subject‐specific differences between the office and ambulatory methods [10],[11]. Covering day–night periods might be critical for the results. As an illustration, two large studies of negative job strain on BP produced divergent results. In the first only slight long‐term effects on BP level were obtained when casual/office BP was used [12]. In the second study, a distinct increase of mean 24‐h ambulatory BP was observed [13]. Additionally, the awareness of high BP might affect the sequentially recorded BP level and reactivity of the investigated subjects [14]. Even if the tested hypotheses were often explicitly stated, various traits were usually applied as single predictors only. This is a potential limitation, since the use of several hypothetical or known predictors enhances the quality of prediction. Therefore, for the above reasons the interpretation of available results is difficult [15–27]

The present aim is to test in a cross‐sectional study the hypothesis that negative affects such as personality traits of Anger–Aggression, Anger Expression Styles, Hostility, Psychic Anxiety and Type A Behavior are not negligible but cooperating modifiers of day–night mean BP and HR. In addition, it is hypothesized that Emotional Reactivity, Inhibited Aggression and Sense of Coherence modify the BP increasing effects of the anger–aggression–hostility complex. We base the hypotheses on previous observations and theories. In contrast to published reports, we used a random sample of employed, middle‐aged men who were unaware of their BP status. In particular, we covered a 24‐h recording period and tested daytime and night‐time periods separately.

Subjects and methods

A computer‐generated random sample of 150 urban men, 48 to 53 year old, from the total population in Uppsala community was approached by mail. Active and employed subjects were included while 9 subjects on sick leave or medicated with antihypertensive drugs were not included. Eighty‐five men, i.e. 57% of those invited, were completely evaluated by ambulatory BP recording followed immediately or within 4 weeks at the latest, by self‐reports. The results of the self‐reports in our normative study [28] and the presently analyzed sample tested with ambulatory BP were very similar.

BP and HR were recorded during a 24‐h period either on a working day (77 cases) or in cases where the job activity would interfere with the recording [8], on a non‐working day. A SpaceLabs 90207 BP monitor with the pressure cuff on the left arm started recordings automatically at 20‐min intervals day and night. At least 90% of the 72 recordings scheduled were accepted by the criteria programmed in the pressure monitor. For separate analyses of the waking and sleeping data, the daytime from 08:00 to 20:00 h and night‐time between 00:00 and 06:00 h were chosen. In this case, a tentative search for a distinct day‐to‐night mean BP difference in the whole group of subjects gave the largest difference between active day and night. These basic data are summarized in Table I. Mean values for 24‐h, daytime and night‐time periods were used as statistical outcome variables.

Table I. Basic data of the present sample, ambulatory heart rate (HR; beats/min), blood pressure (BP; mmHg).

Men (n = 85)	Mean	SD	Range
Age, years	51	2.0	47–54
BMI, kg/m^2	24.4	2.1	22–28
SBP
24‐h	129	12.8	108–161
Daytime	135	14.3	104–181
Night	114	14.8	90–155
DBP
24‐h	80	8.4	62–101
Daytime	86	9.6	65–113
Night	69	8.9	50–90
PP
24‐h	49	6.8	38–75
Daytime	49	6.5	38–72
Night	46	8.4	35–85
HR
24‐h	72	9.3	52–94
Daytime	77	9.9	57–99
Night	62	9.2	43–89
SBP day–night, mmHg (SBP night/day)	20 (0.849)	8.9 (0.066)	− 7 to + 47 (0.72–1.05)
HR day–night, beats/min (HR night/day)	16 (0.80)	7.4 (0.083)	− 3 to + 37 (0.62 to 1.04)

BMI, body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure; PP, pulse pressure; SD, standard deviation. Daytime from 08:00 to 20:00 h and night‐time from 00:00 to 06:00 h.

As statistical predictors, self‐reports (Table II; [29–36]) were tried as scores of complete scale or subscale. The scales of statements/items are graded in steps resulting in scale points for each item and sum of points of all items in a complete scale. In principle, they consist of ordered categorical data. The items on a scale are considered of the same value, and different scales are considered equally important; both these assumptions are subjective. We have used them as continuous predicting variables even though we are aware of the fact that this statistical approach is debatable.

A correlation matrix and simple and multiple regression analyses were used in the StatView II program. Squared correlation adjusted for the number of predictors (adj. R², %) was considered a cautious measure of goodness‐of‐fit in the multiple regressions. Unlike the squared correlation coefficient (R²), the adjusted squared correlation coefficient (adj. R²) increases only if the new added predictor improves the model more than would be expected by chance. The stepwise method eliminates weak and the weaker one of correlated predictors. However, the correlated/weaker predictors might be of interpretational interest, since they share common roots for the prediction. The inevitable multiple testing requires caution in evaluating p‐values.

Table II. Personality self‐reports.

Complete self‐report	Subscale
Emotional Reactivity [18],[33] (Proneness to sustained emotional arousal in the face of stressful events) Type A Behavior [29] (Excessively time‐conscious, highly competitive, hostile and aggressive)	Large and Lasting Emotions Intrusive Emotions Anticipation Lack of Emotional Control Time‐Pressured Drive Dominant—Competitive Anger Outward Suspicious Hostility
Trait Anger STAXI‐1 [30] (Situations perceived as annoying and responding with anger)
Anger Expression Styles STAXI‐1	Anger Expressed (e.g. provoked aggression) Anger Suppressed (e.g. secret criticism) Anger Controlled (attempt to control expressions of anger)
Karolinska Scales of Personality [31],[32]	Indirect Aggression (e.g. spreading hostile gossip, angry sulking) Verbal Aggression (e.g. yelling back, quarrelling) Inhibition of Aggression (low assertiveness, e.g. quarrel is meaningless) Psychic Anxiety (e.g. lack of self‐confidence)
Brief Symptom Inventory (Psychological distress) [34]	Interpersonal Sensitivity Anxiety Depression Hostility
Sense of Coherence (World view over time: close to perceived mental and physical health) [35],[36].

Results

We present results on systolic BP (SBP) only; effects on diastolic BP (DBP) and pulse pressure (PP) were directionally similar; however, on DBP they were often weaker.

Simple regressions predicting 24-h, daytime and night-time SBP

The scales measuring traits of Anger, Anger Outward, Dominant–Competitive, Verbal Aggression, Indirect Aggression, and Large and Long Emotions were more or less positively correlated. They modulated SBP somewhat upwards. Correlated scales Anxiety and Inhibited Aggression modified 24‐h SBP somewhat downwards. With these predictors, the sizes of the explained variation were tiny, with adj. R² = 3.3 (p = 0.056) to 14% (p = 0.003).

Additionally, the complex Type A Behavior was also positively related to 24‐h SBP (adj. R² = 4.7%). Two subscales of this complex, Anger Outward and Dominant–Competitive, were responsible for this weak effect, while the remaining two scales Time‐Pressured Drive and Suspicious Hostility had no impact at all.

Multiple regressions predicting 24‐h BP (Table III)

Forward stepwise regression and adj. R2 correlation excluded the weak/correlated predictors and left only four independent (i.e. low correlated) ones. Trait Anger, Anger Expression Styles, Large and Lasting Emotions, and Anxiety explained, as expected, more variation of 24‐h SBP (adj. R2 = 25.6%), than when each was used separately.

The hypothesized decreasing effect on 24‐h SBP by a high Sense of Coherence was not observed. Sense of Coherence was negatively related to Psychological Distress (r = − 0.62), Anxiety (r = − 0.57), Suspicious Hostility (r = − 0.43), Anger Outward (r = − 0.42), Trait Anger (r = − 0.29) and Job Conflict (r = − 0.29). The hypothesized augmentation of 24‐h SBP by Emotional Reactivity was not observed. Emotional Reactivity was related to the positive BP predictor Trait Anger (r = + 0.39) but also to the negative BP predictor Anxiety (r = + 0.51), which diluted its hypothesized impact in multiple regression models.

Table III. Predictors of 24‐h/day/night systolic blood pressure (SBP) in multiple regression models.

	Adj. R^2, %, p for regr.	Regr. coefficient, mmHg/scale point	p‐value	Between subjects, mmHg
Independent predictors		Outcome for 24-h SBP
↑Trait Anger	25.6%, p < 0.0001	0.75	0.0013	+ 18
↑ Anger Expression Styles		0.66	0.0264	+ 13
↑ Large & Lasting Emotions		1.15	0.0380	+ 11
↓ Anxiety		− 0.58	0.0345	− 13
Independent predictors		Outcome for daytime SBP
↑ Large & Lasting Emotions	16.8%, p = 0.0006	+ 1.48	0.0184	+ 15
↑ Indirect Aggression		+ 1.43	0.0156	+ 16
↓ Anxiety		− 1.00	0.0007	− 23
Independent predictors		Outcome for night-time SBP
↑ Verbal Aggression	15.7%, p = 0.0006	+ 2.03	0.0012	+ 30
↓ Anxiety		− 0.75	0.0162	− 17

↑ denotes an augmenting, and ↓ an attenuating predictor. Adjusted R² indicates the size of explained variation in %. p is the probability of the total regression. The details of analysis are shown as regression coefficients for each predictor and corresponding p-value. Finally the estimated effect of specific predictors between subjects (= 4 standard deviations of scale points of a predictor) is shown.

Prediction of heart rate

Only the trait Suspicious Hostility was positively associated with HR during 24 h (adj. R² = 7.4%, p = 0.008), though in post hoc analysis two items from this scale, i.e. Distrust of other people and a feeling of one—s own Vulnerability were responsible for the high positive prediction of daytime, night‐time and 24‐h HR (adj. R² = 16.8%, p < 0.0001), while the rest of the items of Suspicious Hostility were, in respect to HR, not effective.

Discussion

We sought to determine the associations between some personality measures and levels of ambulatory mean values. First, we found upward modifying effects of several related anger–aggression personality traits. The usual expression of the traits can be illustrated as provoked anger and hidden criticism. Among the measures of anger–aggression only the trait Verbal Aggression increased night‐time SBP much more than daytime SBP and consequently diminished SBP dipping, while other measures of anger had weaker effects. The augmenting effect on night BP of Verbal Aggression might be a carry‐over effect from daily experiences and these possibly disturb night sleep. Our finding is partly in accordance with observations where college students with strong Anger and Hostility traits and angry moods during recording had higher levels of ambulatory BP, especially of DBP during sleep. Good moods had an opposite effect on sleep DBP (20).

Anxiety as a trait had a distinct downward BP modifying effect while Inhibited Aggression had only a weak downward effect. As expected, the traits Anxiety and Inhibited Aggression were closely related. The BP inhibiting effect of Anxiety appears to depend on items expressing low self‐confidence and cautious behavior. The small mitigating effect of Inhibited Aggression reflects a non‐quarrelling approach in interpersonal relations. A previous study suggested that persons with high Trait Anxiety attempt to passively avoid or withdraw from stressful situations [37], which probably effectively lowers arousal and ambulatory BP. In some contrast to this explanation, negative moods throughout the monitoring combined with traits of Anxiety and of pessimism resulted in elevated daytime ambulatory BP [22]. Thus both the negative and positive emotional states during recording in addition to personality traits appear to be important modifiers of BP [20],[22].

The hypothesized augmenting effect of Emotional Reactivity on 24‐h SBP via anger‐related traits and styles was not observed in our models. However, only the Emotional Reactivity subscale Large and Lasting Emotions increased selectively the daytime SBP. In a previous study, the complete Emotional Reactivity elevated daytime ambulatory SBP, though the effects of the subscales were not differentiated [18]. A part of this discrepancy might depend on the ethnic type of population included.

The assumed moderating effects of a strong Sense of Coherence on BP via the complex of anger, aggression and hostility were not present in the regression models. However, as expected, Sense of Coherence was strongly negatively related to Psychological Distress, Anxiety and Suspicious Hostility. It was also negatively related to different sorts of anger and conflict. Probably, highly experienced Sense of Coherence is the opposite of aggressive, defensive and frustrating life experiences, and does not mediate statistically detectable activation or inhibition of cardiovascular arousal.

Increase in HR was related in a distinct way only to Distrust of other people and to perception of one's own Vulnerability. These perceptions seem to be the innermost part of awareness of insufficient social support and low income, as suggested by some published evidence. A four beats higher office HR was found in subjects from a socially disadvantaged class compared with those from a well‐off class in a male population sample [38]; similarly, a perceived lack of social support was associated with a somewhat higher office HR [39]. Perhaps more relevant is the finding of elevated ambulatory daytime HR both at work and at home, which was related to low‐prestige occupation, negative mood and interpersonal conflicts [40].

In conclusion, our results support the hypothesis that emotions and behavior belonging to the anger–aggression complex augment day and night BP; in contrast, reserved or timid behavior attenuates day and night BP. Some traits, however, affect specifically day or night periods. Verbal Aggression augments night SBP while Large and Lasting Emotions augment only daytime SBP. All effects are most probable when the personality traits are repeatedly expressed or used as a way of coping with inevitable life situations. They might be physiologically plausible modifiers of cardiovascular functions even during sleep.

It is not impossible that the augmenting and attenuating effects could, in some extent, be explained by chance due to multiple testing. However, our interpretation relied on the multiple regression analyses, which exclude weak/correlated predictors and resulted in very high significances. Also, the positively related predictors point out, as a minimum, the same directional outcomes and shared psychological content. Negatively related predictors had divergent outcomes and contrasting behavioral content. Thus the ensuing picture of intertwined determinants of BP seems to be coherent.

The study is limited in terms of its size. Therefore, we restricted the number of predictors in the multiple regression models to a minimum. The psychosocial scales supposed to “measure” different psychological concepts contain, in part, nearly identical items. These were in post‐hoc, at best, correlated in our material up to r = 0.6. This dilutes the statistical differentiating ability of single items and complete scales in this and in similar studies. Further, the statements/items in a specific self‐report are probably not uniformly associated with similar situational psycho‐physiological effects on BP. Some items state hypothetical situations only. Another weakness is that the accuracy of the psychosocial components and BP variables is not under repeated control. Finally, only a minority of our men had 24‐h ambulatory hypertension or nondipping BP. Thus for natural reasons these conditions are not covered in our population sample.

In general, ambulatory BP and HR recordings are prone to larger day‐to‐day variation than currently appreciated. The mean values of night recordings are not always characteristic of the usual sleep condition; here the true mean value of readings suffers from changing cuff position in relation to the heart level and the small number of recordings. The BP components SBP, DBP and PP show an increasing size of relative within‐subject variation [41]. This puts the statistical evaluation of DBP and even more of PP at a disadvantage versus SBP. Therefore we consider the mean 24‐h SBP to be the most reliable variable. In contrast to the components of BP, the interpretation of strong effects on HR in simple regression is simple.

It was beneficial that the self‐reports used in this study were translated, critically tested and used as psychological tools in Sweden. The results were published or available by direct contacts with the authors. It was advantageous that the scales used in this ambulatory BP study were independently applied in a separate random sample of the identical population. The participants were mature men of Swedish descent with rather uniform attitudes; typically, they avoid causing or starting private conflicts or openly expressing criticism. The participants who completed the study were interested in the study; they did not report the procedure of ambulatory recording as being difficult. Perhaps the invitation for evaluation at the Stress Clinic caused some self‐selection of vulnerable subjects or those volunteering in good faith. Our small sample produced a very similar group mean 24‐h BP to the level 131/75 mmHg found in large Danish and Swedish population samples of non‐medicated men [42],[43].

In the future, repeated and reliable personality measures and ambulatory recordings during verified sleep periods and verified active daytime periods might improve the discriminative power of the analyses presently used. Since the personality traits need to be activated to show their effect during the ambulatory recording, it would help to test the emotional state and, separately, the corresponding emotional trait.

Acknowledgement

Professors Charles D. Spielberger, Svorad Stolc Sr, Sam Melamed, Arne Öhman, Örjan Sundin, J. Petter Gustavsson, Britt af Klinteberg, Randall S. Jorgensen, George Fodor and University Lecturer Judit Krisztina Lindqvist all helped us with valuable advice and published and unpublished results of psychological scales.