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Experimental Aging Research: An International Journal Devoted to the Scientific Study of the Aging Process Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/uear20

Influence of contextual variables on blood pressure in the elderly a

Thomas J. Harbin & Walter R. Cunningham

a

a

Department of Psychology , University of Florida , Gainesville, Florida, 32611, U.S.A. Published online: 27 Sep 2007.

To cite this article: Thomas J. Harbin & Walter R. Cunningham (1978) Influence of contextual variables on blood pressure in the elderly, Experimental Aging Research: An International Journal Devoted to the Scientific Study of the Aging Process, 4:6, 521-534, DOI: 10.1080/03610737808257173 To link to this article: http://dx.doi.org/10.1080/03610737808257173

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INFLUENCE OF CONTEXTUAL VARIABLES Downloaded by ["Queen's University Libraries, Kingston"] at 07:45 01 January 2015

ON BLOOD PRESSURE IN THE ELDERLY THOMAS J. HARBIN WALTER R . CUNNINGHAM Department of Psychology University of Florida Gainesville,Florida 3261 1 U.S.A.

Harbin, T. J. & Cunningham, W.R. Influence of Contextual Variables on Blood Pressure in the Elderly. Experimental Aging Research, 1978, 4(6), 521-534. This research evaluated determinants of blood pressure in elderly subjects. Measurements were obtained from 30 subjects in three contexts; in the home measured by the subject, in the home measured by the experimenter, and in a psychophysiological laboratory measured by the experimenter. Four measurements were obtained in the two home conditions and two were obtained in the laboratory condition. For systolic blood pressure, the effects of condition, repeated measurement, and order of treatment presentation were significant., For diastolic blood pressure, the effect of condition was significant. A comparison of sample variances revealed greater variances for systolic blood pressure. It was concluded that initial blood pressure measurements obtained in a laboratory should be regarded as distinct from those obtained later, as the early measurements may be subject to elevation imposed by the context. Due to differing patterns of results for systolic and diastolic pressures as well as differences in variability, it was concluded that there exist conceptual problems with a construct such as mean arterial pressure.

This research was supported by a Grant-in-Aid of Research from Sigma Xi, the Scientific Research Society of North America, by the Graduate School of the University of Florida, and by the University of Florida Center for Gerontological Studies and Programs. The authors wish to thank Drs. F. Dietrich, Department of Statistics, University of Florida, and W.K. Berg, Department of Psychology, University of Florida, for assistance in research design and statistical analysis. Many thanks are also extended to the Director, Anita Tassinari, and the members of the Alachua County Older Americans Council, Inc. of Gainesville, Florida for assistance in subject recruitment. T. J. Harbin and W. R. Cunningham are also affiliated with the Center for Gerontological Studies and Programs, University of Florida, Gainesville, Florida, 3261 1.

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Increased blood pressure has long been recognized as a phenomenon accompanying old age. It is only relatively recently, however, that hypertension has been investigated with regard to its possible contribution to age-related perceptual and cognitive behaviors. Hypertension has been related to decrements on intelligence tests (Wilkie & Eisdorfer, 1971, 1973), memory tests (Wilkie, Eisdorfer, & Nowlin, 1976), and reaction time (Light, 1975, 1978). However, as Spieth (1964) pointed out, the effects of hypertension upon performance are complex and not well understood. In view of the intricacy of the relationships between blood pressure and associated hypertensive disease and these cognitive behaviors, it is incumbent upon researchers to be confident that the particular measure of blood pressure chosen for study be free from unwanted variability imposed by the measurement context. The present study was designed to evaluate two sources of potentially artifactual variation: the situation in which blood pressure is measured, and the effects of repeated measurement. Often a particular indicator of blood pressure is investigated without a sound concept of the physiological processes involved. For example, consider mean arterial pressure. Since systolic blood pressure (SBP) is related to strength and volume of cardiac output and aortic elasticity, and diastolic blood pressure (DBP) largely reflects arteriolar resistance (Dustan, Tarazi, & Bravo, 1972), the meaning of a weighted or unweighted average of SBP and DBP is not clear. Furthermore, pathological elevations of SBP and DBP are symptomatic of quite different structural changes. Chronically elevated SBP has been shown to relate to lesions in large arteries (Smirk, 1957) whereas DBP has demonstrated no such relationship (Sommers, McLaughlin, & McAuley, 1962). Diastolic hypertension is symptomatic of thickening and obstruction of small arteries and arterioles (Cohen, Neumann, & Michaelson, 1950; Dustan et al., 1972) producing increased peripheral resistance (Onesti & Moyer, 1967; Weber, Batson, & Birchall, 1967) and small, diffuse cerebral infarcts, or “little strokes” (Hughes & Warren, 1956). Compounding these difficulties of interpretation of mean arterial

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pressure are demographic studies indicating that SBP is sex-related in older cohorts whereas DBP is not (Boe, Humerfelt, and Wedervang, 1957; Winklestein & Kantor, 1967). Finally, a series of studies by Goldman and his colleagues has demonstrated that while blood pressure is related to brain damage as indicated by the Halstead-Reitan Category Test, it is not yet apparent whether SBP or DBP is more strongly associated with this variable (Goldman, Kleinman, Snow, Bidus, & Korol, 1974; Goldman, Kleinman, Snow, Bidus, & Korol, 1975; Kleinman, Goldman, Snow, & Korol, 1977).

In addition to the precautions necessary when choosing an index of blood pressure, blood pressure may vary by situation and such situational effects may interact with the sample selected. For example, there is evidence that the blood pressure of diagnosed hypertensives is higher when measured by a physician in his office than when read at home by the patient (Ayman & Goldshine, 1940). However, this difference was not replicated in a sample of college students selected for high and low blood pressure (Julius, McGinn, Harburg, & Hoobler, 1964). The purposes of this study were threefold. One purpose was to assess differences in blood pressure across three environmental situations, (a) measurements taken in the subject’s home by the subject himself, (b) measurements taken in the subject’s home by the experimenter, and (c) measurements taken in a psychophysiological laboratory by the experimenter. The second purpose was to estimate differences in blood pressure across repeated measurement. A third purpose was to evaluate differentia1 reactions of SBP and DBP across experimental conditions.

Three specific hypotheses were tested. (a) Laboratory measurements were expected to be higher than those of the two home conditions for SBP but not for DBP. This hypothesis was

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based upon a finding by Ayman & Goldshine (1940) that home readings were lower than those obtained in a physician’s office. It was thought that an unfamiliar laboratory may possibly elicit a similar reaction. (b) SBP would decrease over repeated measures but DBP would not. The rationale for this hypothesis was the often encountered reactivity of SBP to anxiety-provoking events (Hyman, 1965, p. 66): It was believed that with repeated measurements, effects due to this variable would decrease. (c) DBP would show smaller sample variability for the three conditions than would SBP. This hypothesis was based upon data which suggest that the variability of SBP was greater than that of DBP for most age groups (Altman, 1959).

METHOD

Subjects

Subjects were 30 elderly community residents, eight males, and 22 females, ranging in age from 58.1 to 85.7 years with a mean of 69.5 and a standard deviation of 5.9. There were 27 whites and three blacks in the sample. Education ranged from 12 to 20 years with a mean of 15.8 and a standard deviation of 2.5. Three hundred ten individuals were contacted by mail and phone from the membership of the Alachua County Older Americans Council, Inc. of Gainesville, Florida. Of these, 72 volunteered to participate. Volunteers were administered a medical questionnaire constructed by the authors and eliminated for any one of the following conditions: history of heart attacks or strokes, present treatment for heart pain, high blood pressure, kidney disease, diabetes, depression, chronic infection, anemia, cancer, poor hearing or vision, present use of any medication tending to affect blood pressure. Thirty nine subjects were eliminated at this stage. T w o subjects were later eliminated due to scheduling difficulties and one for failure to learn to measure her own blood pressure.

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Apparatus

Blood pressure was measured with Abco sphygmomanome Downloaded by ["Queen's University Libraries, Kingston"] at 07:45 01 January 2015

ters and stethescopes, model numbers HR18104-390102 and 058040 respectively. A Marshall Dual Training Stethescope was

used for teaching subjects to measure their own blood pressures. Stethescopes were fitted with adjustable elastic armbands to hold them in place during self-measurement procedures. Procedure All measurements were obtained from the non-dominant a r m (determined by asking the subject) with the subjects seated upright and resting the arm on a table at approximately heart-level. No difficulties were encountered by subjects in learning the self-measurement technique with the exception of one subject whose data were subsequently eliminated from the analysis. In both the self-determined and experimenter-determined, at home conditions, measurements were made in the morning and again in the afternoon of one day and were repeated on the second day following, for a total of four measurements in each condition. Morning and afternoon measurements were separated by a minimum of two hours. In the self-determined condition, the subject was called by the experimenter and made the measurements while the experimenter waited on the telephone. This was done so that any difficulties encountered could be immediately dealt with by the experimenter. In the laboratory condition, measurements were obtained immediately upon entering the laboratory and again immediately following a simple reaction time task. These measurements were separated by approximately 15 minutes.

Measurement conditions were arranged in two 3x3 latin squares balanced for residual effects (Cochran & Cox, 1957). Five subjects were assigned to each of six possible orders of conditions. Blood pressure was measured in accordance with recommendations by the American Medical Association (Kirkendall,

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Burton, Epstein, & Freis, 1967). Phase V (disappearance of sounds) was used rather than Phase IV (muffling) for determination of diastolic pressure because it was thought that subjects would be able to more accurately make the former discrimination. This procedure has been found beneficial for obtaining reliable self-measures of diastolic blood pressure (Ayman & Goldshine, 1940). RESULTS Four analyses of variance were carried out. This was necessary in order to analyze SBP and DBP separately and in order to test initially for repeated measure effects in the self-determined and experimenter-determined, at home conditions before evaluating condition effects for all three measurement conditions. Data from the self-determined and experimenter-determined, at home conditions were analyzed for changes over repeated measures by means of a 2 (conditions) x 4 (repeated measures) x 30 (subjects) design (Bruning & Kintz, 1968), undertaken separately for SBP and DBP. For SBP, a significant effect due to condition was found, F (1,29) = 17.73, p 180

50

s

E

L

Condition Figure 3 . Variances of blood pressures across conditions (Self-determined (S), Experimenterdetermined, at home (E),and Laboratory-measured (L)). S = systolic, D = diastolic.

MAP

DBP

SBP

Blood Pressures

X

S.D.

X

S.D.

-X

S.D.

-

115.13 11.58

81.77 8.39

148.50 18.79

1

114.08 10.51

80.80 7.74

147.37 18.70

2 3

111.83 12.17

79.67 9.51

144.00 18.93

Self-Measurements

111.24 11.35

79.76 8.75

142.72 19.25

4

104.32 10.25

70.40 7.40

138.23 16.73

1

101.60 11.71

69.13 8.35

134.07 19.44

2

102.52 10.93

70.20 9.81

134.83 17.31

3

Experimenter-Measurements, in home.

Mean Systolic [SBP], Diastolic [DBP], and Mean Arterial [MAP] Blood Pressures Across Conditions and Measurements.

TABLE 1

100.77 12.51

68.37 9.99

133.17 18.64

4

105.27 12.52

73.53 9.78

137.00 18.61

1

100.13 10.20

71.37 8.69

128.90 15.54

2

LaboratoryMeasurements

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22

VI

w 0

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DISCUSSION The results of the repeated measures analysis revealed a significant decrease in SBP but not in DBP over the four repeated measures. This finding suggests two precautions for future research employing blood pressure. Investigators obtaining repeated measurements over the course of a study should probably refrain from using averages which include both early and later measurements since it is apparent that early measurements are subject to systematic influences not present in later measurements. Secondly, any weighted or unweighted average of SBP and DBP (such as mean arterial pressure) will present conceptual problems, especially for initial measurements. This is due to the fact that SBP but not DBP decreased over repeated measures.

Results for both SBP and DBP yielded significant condition effects, though not in the hypothesized direction. For both pressures, the self-determined condition was higher than both the experimenter-determined, a t home and laboratory conditions. The argument could be advanced that hearing deficits or cautiousness on the part of the subject accounted for these results. However, if either of these were important influences, the SBP in the self-determined condition would be expected to be lower not higher than in the other conditions. Subjects listening for the onset of Phase I sounds as the pressure in the sphygmomanometer decreased, would, if hard of hearing or overly cautious, detect them later thus underestimating the true pressure. This was not found. This result was therefore interpreted as being due to anxiousness on the part of the subjects induced by unfamiliarity with the procedure and by a desire to make accurate readings. This interpretation was supported by spontaneous remarks by several subjects. The absence of a difference between the experimenterdetermined, at home and laboratory conditions w a s puzzling, especially in light of the significant decrease discovered for the

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two measurements in the laboratory condition. In view of the fact that significant effects were found for repeated measures, it was thought that a difference between the experimenterdetermined, at home and laboratory conditions could possibly be obscured by effects due to repeated measurement. This hypothesis was tested by comparing the first laboratory measure from the two groups which received the laboratory conditions first with the first experimenter-determined, at home measure from the two groups which received the experimenterdetermined, at home conditions first. In other words, these were the first of the ten measurements obtained from the individuals in these four groups. For SBP, there was no significant difference. For DBP, however, the difference was significant, t (18) = 2.02, p < .05. Due to the post hoc nature of this comparison, it should be interpreted with caution. It does suggest, however, that measurements of blood pressure acquired in the laboratory may be elevated in comparison with measurements made in the home. This, together with the significant decrease found between the two laboratory measurements suggests that initial laboratory measurements should be considered separately from those obtained later, and that both early and late measurements should be reported. The effect of order of conditions was significant for SBP but not for DBP. The meaning of th% result is unclear, but presumably demonstrates the greater influence of contextual variables upon SBP. The observed relationship between the variances of SBP and DBP suggests that the majority of the variability of an average of SBP and DBP would be due to SBP. Thus, in the original analyses, the second and third hypotheses, but not the first, were confirmed.

In summary, these results indicate that SBP is more susceptible to situational determinants than is DBP, and in addition, that the variability of SBP is greater than that of DBP. These

findings, in conjunction with the different physiological prorces-

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ses affecting the two pressures suggest serious conceptual problems with research attempting to establish relationships between mean arterial pressure and cognitive behavior. However, for Purposes such as clinical diagnosis, mean arterial pressure may have its uses. A cautionary note is appropriate. Due to the characteristics of the present sample, generalizability of these results is limited. The individuals selected for participation in this study constituted an unusually healthy and well-educated group of elderly people. Experiments involving different age cohorts or subjects with more serious health problems (particularly cardiovascular disease) may well uncover a different pattern of results.

REFERENCES ALTMAN, P. L. (Ed.) Handbook of Circulation. Philadelphia: Saunders Publishing Co., 1959, 105. AYMAN, D., & GOLDSHINE, A. D. Blood pressure determinations by patients with essential hypertension: The difference between clinic and home readings before treatment. American Journal of the Medical Sciences, 1940, (200), 465-474. BOE, J., HUMERFELT, S., & WEDERVANG, F. The blood pressures in a population. Acta Medica Scandinavica, 1957, Supplement 321. BRUNING, J. L., & KINTZ, B. L. Computational handbook of statistics, Glenview, Ill: Scott, Foresman, & Co., 1968. .COCHRAN, W. G., &COX, G. M. Experimental designs(2nd. ed.). New York: John Wiley & Sons, Inc., 1957. COHEN, A.M., NEUMANN, E., & MICHAELSON, I.C. Involutionary sclerosis and diastolic hypertension. Lancet, 1960, ( 2 ) , 1050-1051. DUSTAN, H. P., TARAZI, R. C., &BRAVO, E. L. Physiologic characteristics of hypertension. American Journal of Medicine, 1972, (52), 610-622. GOLDMAN, H., KLEINMAN, K. M., SNOW, M. Y., BIDUS, B. R., &KOROL, B. Correlation of diastolic blood pressure and signs of cognitive dysfunction in essential hypertension. Diseases of the Nervous System, 1974, (35), 571-572. GOLDMAN, H., KLEINMAN, K. M., SNOW, M. Y., BIDUS, D. R., & KORAL, B. Relationships between essential hypertension and cognitive functioning: Effects of biofeedback. Psychophysiology, 1975, (12), 569-573. HUGHES, W., & WARREN, P. K. G. Chronic cerebral hypertensive disease. Journal Of the American Geriatric Sociery, 1956, (4), 8-17. HYMAN, H. T. Differential diagnosis: an integrated handbook. Philadelphia: J. B. Lippincott Co., 1965.

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JULIUS, S., McGINN, N. F., HARBURG, E., & HOOBLER, S. W. Comparison of verious clinical measurements of blood pressure with the self-determine technique in normotensive college males. Journal of Chronic Diseases, 1964, (17), 391-3%. KIRKENDALL, W. M., BURTON, A. C., EPSTEIN, F. H., &FREIS, E. D. Recommendations for human blood pressure determination by sphygmomanometers. Circulation, 1967, (36), 980-988. KLEINMAN, K.’M., GOLDMAN, H., SNOW, M.Y., & KOROL, B. Relationship between essential hypertension and cognitive functioning 11: Effects of biofeedback training generalized to non-laboratory environment. Psychophysiology, 1977, (14). 192-197. LIGHT, K. C. Slowing of response time in young and middle-aged hypertensive patients. Experimental Aging Research, 1975, (l), 209-227. LIGHT, K. C. Effects of mild cardiovascular and cerebrovascular disorders on serial reaction time performance. Experimental Aging Research, 1978, (4), 3-22. ONESTI, G. & MOYER, J. Hypertension past 60. Geriatrics, 1967, (22), 192-199. SMIRK, F. H. Arteriosclerosis and hypertension. In W. Hobson (Ed.), Modern trends in geriatrics. New York: Paul B. Hoeber, Inc., 1957. SOMMERS, S. C., McLAUGHLIN, R. J., & McAULEY, R. L. Pathology of diastolic hypertension as a generalized vascular disease. American Journal of Cardiology, 1962, (9), 653-657. SPIETH, W. Cardiovascular health status, age and psychological performance, Journal of Gerontology, 1964, (19), 277-284. WEBER, G. F., BATSON, H. M., & BIRCHALL, R. Arteriosclerotic hypertension: Often misdiagnosed, overtreated. Geriatrics, 1967, (22), 131-133. WILKIE, F. L. & EISDORFER, C. Intelligence and blood pressure in the aged. Science, 1971, (172), (3986), 959-962. WILKIE, F. L. & EISDORFER, C. Systemic disease and behavioral correlates. In L. F. Jarvik, C. Eisdorfer, & J. E. Blum (Eds.), Intellectual Funcrioning in Adults, New York: Springer Publishing Co., 1973. WILKIE, F. L., EISDORFER, C., & NOWLIN, J. B. Memory and blood pressure in the aged. Experimental Aging Research, 1976, (2), 3-16. WINKLESTEIN, W. & KANTOR, S. Some observations on the relationships between age, sex, and blood pressure. In J. Stamler, R. Stamler, & T.N. Pullman (Eds.), The epidemiology of hypertension, New York: Grune & Stratton, 1967.

Received September 20. 1978; accepted November 7, 1978.

Influence of contextual variables on blood pressure in the elderly.

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