Clin Auton Res (2003) 13 : 427–432DOI 10.1007/s10286-003-0124-4 RESEARCH ARTICLE

Stefan DuschekNathan WeiszRainer Schandry

Reduced cognitive performance and prolonged reaction time accompany moderate hypotension

Introduction

Hypotension is defined as a systolic blood pressure level(SBP) below 100 mmHg for females and 110 mmHg formales, regardless of the diastolic blood pressure (DBP)[1, 2]. By convention however, the DBP should not ex-ceed 60–70 mmHg [3, 4]. Different types of hypotensioncan be distinguished [3]: primary or essential, sec-ondary (e. g., due to blood loss, shock or medication)and orthostatic hypotension (caused by circulatoryproblems, when assuming a standing position). Themost common form is essential hypotension, a chronic

state of lowered blood pressure, independent of thepresence of any other pathological factors.

The prevalence of hypotension has to be consideredas relatively high with especially younger women beingaffected (10–20 % of the female population between 20and 40 years of age [5]). Hypotension was found to havecaused approximately 4.8 million days of work absencein Western Germany (data from the year 1978), nearlytwo million more days than hypertension (3.1 milliondays of work absence) [4]. In contrast to elevated bloodpressure hypotension is commonly not regarded as amedical condition. It was even shown that chronicallylowered blood pressure might be cardioprotective re-

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Received: 31 October 2002Accepted: 9 July 2003

S. Duschek · Prof. Dr. R. Schandry (�)Dept. of PsychologyLudwig-Maximilians-UniversitätLeopoldstr. 1380802 Munich, GermanyTel.: +49-89/2180-5176Fax: +49-89/2180-5233E-Mail: schandry@psy.uni-muenchen.de

N. WeiszDept. of PsychologyUniversität KonstanzKonstanz, Germany

■ Abstract The aim of the presentstudy was to investigate the impactof hypotension on attentional and motor performance. Twenty-six moderately hypotensive sub-jects (mean systolic blood pressure= 108.8 mmHg) were compared to 29 normotensive controls (mean systolic blood pressure= 123.5 mmHg). The participantswere presented with two standardGerman tests of attention (“Auf-merksamkeits-Belastungs-Test”,Test d2; “Zahlen-Verbindungs-Test”, ZVT). Additionally, reactiontimes to acoustic signals were mea-sured. The hypotensive groupshowed significantly prolongedreaction times (p = 0.007) as well as reduced performance speed(p = 0.004) and lower concentrationcapacity (p = 0.014) in the test d2.In the ZVT as well a slightly poorerperformance in hypotensives was

observed (p = 0.088). Moreover, sig-nificant partial correlations be-tween systolic blood pressure andthe performance measures withage as covariate were found (per-formance speed: r = 0.28; concen-tration capacity: r = 0.22; reactiontime: r = 0.33). A lowered cerebralperfusion in hypotensives and analtered activity of baroreceptorslocated in the carotid sinus are dis-cussed as possible underlying psy-chophysiological processes mediat-ing the relationship between bloodpressure and cognitive perform-ance. This study is the first to pro-vide empirical evidence for the re-lation between attentional deficitsand even moderately loweredblood pressure.

■ Key words blood pressure · hy-potension · cognitive performance ·attention · reaction time

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sulting in higher live expectancy compared to nor-motension and hypertension [6, 7].

Nevertheless, the impact of hypotension on personalwell-being and quality of life should not be underesti-mated. Early studies in the 1920s [8, 9] associated hy-potension to “neurasthenic” symptoms, such as tired-ness, weakness, dizziness and a tendency to faint.Contemporary studies reported symptoms like dizzi-ness, headache, lack of appetite, palpitations, reduceddrive and concentration, drop in performance, en-hanced urge for sleep, cold limbs and problems gettingstarted in the morning (see e. g. [4, 10, 11]).

A possible association between hypotension, espe-cially the orthostatic form, and the chronic fatigue syn-drome is discussed in the literature (see e. g. [12, 13]).Orthostatic symptoms were reported in a substantialportion of patients suffering from this disease. Further-more, chronic fatigue syndrome symptoms seem to im-prove in a subset of patients using therapy directedagainst orthostatic hypotension [14].

In studies on typical personality traits [15, 16] higherscores in neuroticism and depression were found to beassociated with hypotension. In contrast to the largenumber of studies investigating cognitive performancein hypertension [e. g., 17–19], a comparable investiga-tion on hypotensive subjects was lacking until recently.

A pioneering study devoted to cognitive deficits inhypotension was presented by Stegagno et al. [20]. Here,a poorer performance of hypotensive subjects (females,mean SBP = 96.0 mmHg) both in a verbal short-termmemory test and in a mental arithmetic task as well asprolonged reaction times to acoustic stimuli were ob-served as compared to normotensive controls.

A second study was conducted by Costa et al. [21],also comparing hypotensive (mean SBP = 98.3 mmHg)to normotensive females. In the hypotensive group theyfound significantly lower scores on two standard Ger-man tests measuring attentional performance with ahigh load on speed of cognitive processing (“Aufmerk-samkeits-Belastungs-Test”, Test d2 [22]; “Zahlen-Verbindungs-Test”, ZVT [23]). As in the Stegagno et al.[20] study, poorer performance in a verbal recognitiontask was observed.

In a recent study from our lab [24], hypotensivesubjects (female participants with mean SBP = 101.8mmHg) performed significantly poorer than controls ina computer test assessing attentional flexibility [25].

In summary, these results can be regarded as a firstindication of cognitive deficits related to essential hy-potension, especially in the field of attention. The pres-ent study aimed at the question whether an impairmentin attention processes can also be found in subjects withonly mild hypotension. Therefore we assessed subjectswith SBP < 115 mmHg using nearly the same tests asCosta et al. [21], comparing the attentional performanceof this sample to that in normotensive controls.

Material and methods

■ Subjects

A total of 55 subjects participated in the study. The gender distribu-tion as well as the means for age, SBP and DBP in the sample are givenin Table 1. All of the participants were students at the University ofMunich who were recruited through advertisements throughout thecampus.Severe physical diseases,psychiatric disorders,and the use ofmedication affecting the cardiovascular system or psychoactivedrugs were defined as exclusion criteria.

■ Material

The “Aufmerksamkeits-Belastungs-Test” (Test d2) [22] as well as the“Zahlen-Verbindungs-Test” (ZVT) [23] were applied. Both of thesepaper-pencil tests are widely in use in the German speaking countriesto assess visual selective attention and speed of cognitive processing.

Aufmerksamkeits-Belastungs-Test (Test d2)

This test consists of a task in which a target stimulus has to be iden-tified among a variety of distracter items. The target stimulus is de-fined as the letter d with two apostrophe marks each of which may belocated above or below the letter. The letters p and q with differentnumbers of apostrophe marks as well as the letter d with one, three orfour apostrophe marks serve as distracters. The stimuli are arrangedin 14 rows containing 47 letters each. For each row the subject has 20seconds to work, then she/he is instructed to immediately move on tothe next row. Attentional performance can be quantified as perform-ance speed (total number of processed items), concentration capacity(number of correct responses) and percentage of mistakes.

Zahlen-Verbindungs-Test (ZVT)

The ZVT is a variant of the “Trail Making-Test”, the latter being widelyused in Anglo-American countries.Numbers from 1 to 90,distributedpseudorandomly on a page, have to be connected sequentially as fastas possible. The test consists of four of these matrices. The timeneeded to complete each of the matrices is measured and a total scoreis calculated as the average of the four results.

n Gender Mean age Mean SBP Mean DBPdistribution in years in mmHg in mmHg

Hypotensives 26 1 m, 25 f 27.77 (8.20) 108.77 (4.83) 69.50 (4.63)

Normotensives 29 10 m, 19 f 24.59 (5.12) 123.45 (7.61) 80.00 (5.85)

Total 55 11 m, 44 f 26.09 (6.88) 116.51 (9.78) 75.04 (7.46)

m male; f female

Table 1 Gender distribution, age, SBP and DBP inthe sample (SD in parentheses)

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Motor reaction task

Simple reaction times (RT) to acoustic signals (approx. 60 dB) weremeasured.Stimulus generation and RT recording were carried out au-tomatically. The subjects were instructed to press a button as quicklyas possible after the tone. Each participant completed 15 trials.

■ Procedure

In a screening session,blood pressure was assessed in each of the sub-jects approximately one week before the actual experiment. It wasrecorded sphygmomanometically after a resting period of ten min-utes.A second blood pressure reading took place a few minutes beforethe experiment. Based on the mean SBP of these two assessments,participants were assigned to one of the two experimental groups:mean SBP-values below or equal 115 mmHg were regarded as “mod-erately hypotensive”, values above 115 mmHg as “normotensive”.Subjects with SBP above 140 mmHg were classified as hypertensivesand therefore excluded from the study.

The experiment was conducted as follows: after the Riva-Rocci as-sessment of blood pressure, the RT task was carried out. Then the testd2 and the ZVT were presented. Throughout the experiment SBP andDBP were recorded continuously using a Finapres BP Monitor,Ohmeda 2300 (for reviews of this method see [26] and [27]). In orderto evaluate task-induced changes of BP baseline measurements (restperiods of 10 min) were taken preceding both of the cognitive tests aswell as the RT task.

■ Data analysis

To compare the scores on the cognitive tests and the reaction times of hypotensives and controls, a multivariate analysis of variance(MANOVA) was computed.Age and gender were used as covariates inorder to control for their effects on performance.Additionally, partialcorrelations between SBP and the performance measures were calcu-lated over the total sample with age being partialed out. The continu-ously recorded SBP and DBP were averaged over each of the rest pe-riods and phases of cognitive testing. The resulting means werecompared using t-tests for independent samples (hypotensives vs.normotensives).

Results

■ Blood pressure

Fig. 1 displays the course of SBP throughout the experi-ment in both the hypotensive and the normotensivesample. The mean SBP turned out to be significantlylower in hypotensives measured at the beginning of theexperiment as well as during the execution of each of thecognitive tests and the respective resting phases (allp < 0.05). Similar results were achieved for the DBP.These data confirm that the difference in SBP betweenhypotensives and normotensive remained almost stableduring the entire experiment.

■ Cognitive tests

The ANCOVA concerning attentional performance withage and gender being controlled for revealed the follow-

ing results: in the test d2 performance speed (quantifiedas the number of processed items) was substantiallylower in the hypotensive group (m = 523.23; SD = 64.91)as compared to the normotensive controls (m = 572.69;SD = 67.32; see also Figs. 2a and b). This finding is con-firmed by a highly significant difference between thetwo means (F = 4.97; df = 3; p = 0.004). A similar resultwas obtained for concentration capacity (number of cor-rect responses), again with hypotensives performingsignificantly poorer than normotensives (hypotensives:m = 196.42; SD = 44.24; normotensives: m = 221.38;SD = 47.73; F = 3.92; df = 3; p = 0.014). The percentage of

Fig. 1 SBP in mmHg during the course of the experiment

Fig. 2 a Test d2: Performance speed. b Test d2: Concentration capacity

a)

b)

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mistakes in the test d2 differed only to a small extent be-tween the groups (hypotensives: 6.51 %; normotensives:5.44 %; F = 1.81; df = 3; p = 0.16).

In the ZVT, a slightly poorer performance in hy-potensives was also observed (normotensives:m = 59.31 s; SD = 12.19 s; hypotensives: m = 62.34 s;SD = 13.55 s). However, this difference reached only asignificance level of p < 10 % (F = 2.31; df = 3; p = 0.088).

■ Reaction time

The difference between the RTs of the two groups washighly significant (F = 4.49; df = 3; p = 0.007). As dis-played in Fig. 3 the mean RT in the hypotensive sample(m = 367.47 ms; SD = 54.75 ms) was far longer than innormotensives (m = 328.07 ms; SD = 30.21 ms).

■ Correlations between SBP and the performancemeasures

The relation between lowered blood pressure and re-duced attentional performance is confirmed by substan-tial correlations between SBP and the performance mea-sures. The calculated partial correlations of SBP to thetest d2-measures performance speed and concentrationcapacity with age being held constant both turned out tobe significant (performance speed: r = 0.28; p = 0.022;concentration capacity: r = 0.22; p = 0.045). This was alsotrue for the correlation between SBP and the RTs(r = –0.33; p = 0.005). In contrast to this, no considerableassociation was found between SBP and either the per-centage of mistakes in the test d2 or the ZVT score.

Discussion

The results point towards reduced attentional perform-ance related to arterial hypotension confirming theearlier findings by Stegagno et al. [20] and Costa et al.[21]. Moreover, this study is the first to demonstrate cog-

nitive deficits in a group of subjects with only compara-tively mild hypotension (systolic blood pressure below115 mmHg).

The test d2 as well as the ZVT were also employed inthe Costa et al. [21] study. The results in the test d2 couldbe replicated almost exactly in our sample. In contrast tothis, the significant difference between hypotensive andnormotensive subjects in the ZVT found by Costa et al.[21] was only seen as a slight tendency towards poorerperformance in hypotensives. This may be due to thedifferent degree of hypotension in the samples of thetwo studies (mean systolic pressure = 108.8 mmHg inour sample vs. 98.3 mmHg in Costa et al. [21]).

Furthermore, it seems interesting to look at the at-tentional deficits from a taxonomic point of view. Inmost of the common neuropsychological theories, at-tention is not regarded as a single cognitive function.Based on numerous experimental studies generally atleast four distinct components of attention are distin-guished, which can be assigned to different neuronalsystems (see e. g. [28, 29]): general alertness (“arousal”),selective or focused attention,divided attention and sus-tained attention. The prolonged simple RTs in hypoten-sives primarily refer to the component of alertness.Theyreflect a reduced general state of vigilance as well as de-creased readiness to respond to significant environmen-tal stimuli. The test d2 requires attention focused on oneclass of relevant stimuli to the exclusion of irrelevant(distracter) stimuli,and thus has a high load on selectiveattention. The results of the experiment point towards apossible blood pressure-related deficit in this area.

In their theory of attention, van Zomeren andBrouwer [29] proposed two key features of attention: in-tensity and selectivity.While alertness and sustained at-tention primarily refer to the aspect of intensity, tasksinvolving focused or divided attention relate to the di-mension of selectivity. The reduced performance of hy-potensives in the alertness component as well as in se-lective attention indicates an impairment related to bothof these aspects. Thus, the attentional deficits in hy-potension seem to exceed a simple reduction of generalarousal. The components of sustained and divided at-tention have not yet been specifically assessed in hy-potensives.According to subjectively described daily ex-periences of many hypotensives, especially sustainedattention is thought to be strongly affected and thereforewould surely be worth investigating at a quantitativelevel.

Nevertheless, one problem concerning the interpre-tation of our results is that both of the cognitive tests weused have a certain load on motor speed. The extent towhich the poorer performance of hypotensives is due topossible deficits in fine motor functions can not be de-termined based on the studies presented to date. Testsassessing specific processes of attention which put lessemphasis on motor speed have to be employed.Fig. 3 Simple motor reaction times

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Even if the studies presented to date clearly supportthe hypothesis of reduced cognitive or psychomotorperformance in hypotension, the experimental designsused do not allow definite inferences of causality. Thepsychophysiological processes mediating the relation-ship between blood-pressure and performance remain amatter of speculation.

One hypothesis is that hypotension is accompaniedby a lowered cerebral perfusion and a reduced metabolicrate. This explanation is not at all trivial insofar as cere-bral autoregulation keeps the blood flow constant withinwide range of arterial pressure [30, 31]. Possible disturb-ances of autoregulatory processes in essential hypoten-sion have not been investigated so far.

A second possible explanation includes an altered ac-tivity of baroreceptors in hypotension. Baroreceptors inthe carotid sinus are primarily engaged in the regulationof arterial blood pressure. It was shown that in hypoten-sion the threshold for baroreceptor activity is reduced,thus, stabilizing blood pressure at a lower level [32]. Ad-ditionally, baroreceptors play a major role in mediatingcardiovascular influences on brain activity: their excita-tion and inhibition are known to have modulating ef-fects on cortical activation with increased receptor ac-tivity being related to reduced cortical arousal [33, 34].Assuming a hypersensitivity of the baroreceptors to in-creasing blood-pressure in hypotensives, the resultingreceptor-hyperactivity could lead to a generally reduced

level of cortical arousal explaining the prolonged reac-tion times and poorer performance in cognitive tasks.

Another putative explanation for our results is thatreduced personal well-being in hypotensives affectstheir cognitive performance. Studies on orthostatic hy-potension [35] as well as on the essential form [4, 10, 11]reported subjective symptoms of a considerable degree.This potential confound was not controlled in our study.

A number of studies concerned with elevated bloodpressure also showed reduced performance in variouscognitive and psychomotor tests [17–19]. Taking the re-sults from these studies on hypertension together withour findings, an inverted U-shaped relationship be-tween blood pressure and cognitive function may be hy-pothesized with a presumably optimal performance atthe normotensive level (c. f. [21]). This resembles the in-verted U-shaped relationship between arousal and cog-nitive performance as formulated in the so-calledYerkes-Dodson-Law [36, 37]. In both cases the mediat-ing physiological process could be the sympathetictonus. However, to substantiate this assumption, studiesmanipulating sympathetic outflow, for example throughpharmacological interventions, would be necessary.

■ Acknowledgment The authors would like to thank Barbara Wieseand Michael Kleinhenz for their assistance during data collection.Weare also grateful to Julia König for help with the translation of themanuscript into English.

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