A number of studies have reported associations of hypotension with depressive symptoms (Reference Pilgrim, Stansfeld and MarmotPilgrim et al, 1992; Reference Barrett-Connor and PalinkasBarrett-Connor & Palinkas, 1994; Reference Henderson, Korten and JacombHenderson et al, 1997; Reference Stroup-Benham, Markides and BlackStroup-Benham et al, 2000), fatigue (Reference Wessely, Nickson and CoxWessley et al, 1990) or lower well-being (Reference Rosengren, Tibblin and WilhelmsenRosengren et al, 1993). A longitudinal study found that low blood pressure at baseline predicted later depression scores, whereas high depression scores at baseline did not predict later hypotension (Reference Paterniti, Verdier-Taillefer and GenestePaterniti et al, 2000). However, the associations reported have been weak and inconsistent (Reference Gilmore, Green and CopelGilmore et al, 1995; Reference Donner-Banzhoff, Chan and SzalaiDonner-Banzhoff et al, 1997).
Depression and affective systems
One interpretation is that the positive associations in the literature are simply due to selective reporting of Type I errors (Reference Donner-Banzhoff, Chan and SzalaiDonner-Banzhoff et al, 1997). However, another possibility is that depression scales are only weakly tapping the psychological characteristics associated with hypotension. Research into the psychology of emotion has distinguished two independent affective systems, involving positive and negative affect. Whereas anxiety involves the negative affect system, depression involves both high negative affect and (to a lesser degree) low positive affect (Reference Watson, Clark and TellegenWatson et al, 1988; Reference Clark, Watson and MinekaClark et al, 1994). According to Watson et al (Reference Watson, Clark and Tellegen1988), high positive affect is “a state of high energy, full concentration, and pleasurable engagement, whereas low [positive affect] is characterized by sadness and lethargy” (p. 1063). The same authors describe negative affect as “ a general dimension of subjective distress and unpleasurable engagement that subsumes a variety of aversive mood states, including anger, contempt, disgust, guilt, fear, and nervousness, with low [negative affect] being a state of calmness and serenity” (p. 1063). The present study assessed the association of hypotension with measures of depression, anxiety, positive affect and negative affect.
METHOD
Participants were 340 community-dwelling persons aged 77-99 years from the third wave of a longitudinal study based in Canberra and Queanbeyan, Australia (Reference Henderson, Korten and JacombHenderson et al, 1997; Reference Korten, Jorm and JiaoKorten et al, 1999). Blood pressure was measured twice in the interview using an Omron automatic digital blood pressure/pulse monitor (Model HEM-703C) and the results were averaged. Following Barrett-Connor & Palinkas (Reference Barrett-Connor and Palinkas1994), normal systolic pressure was defined as 120-139 mmHg and normal diastolic pressure as 75-84 mmHg. Participants also were given anxiety and depressiion symptom scales (Reference Goldberg, Bridges and Duncan-JonesGoldberg et al, 1988; Reference Mackinnon, Christensen and JormMackinnon et al, 1994) and a range of physical health measures (Reference Korten, Jorm and JiaoKorten et al, 1999). On Wave 3 only, participants were asked to self-complete the Positive and Negative Affect Scales (PANAS; Reference Watson, Clark and TellegenWatson et al, 1988). The PANAS consist of 20 words describing emotions: 10 positive and 10 negative. Participants were asked to rate each word to indicate ‘to what extent you feel this way in general’. There was a five-point rating scale ranging from ‘very slightly’ or ‘not at all’ to ‘extremely’.
Multiple linear regression analyses were carried out to predict the affect score from hypotension and hypertension (dichotomous variables). To control for potential confounders, additional regression analyses were carried out with the confounders entered as simultaneous predictors.
RESULTS
Table 1 shows the mean scores on depression, anxiety and affect measures for the blood pressure groups. Diastolic hypotension was weakly associated with higher depression (unstandardised β=0.55, P=0.031), was not associated with negative affect and was strongly associated with lower positive affect (β=-3.21, P=0.0002). The association with positive affect was found separately in males and females and when those taking antihypertensive medication were excluded (not shown). Systolic hypertension was associated with higher positive affect (β=2.12, P=0.015), but the number of participants with systolic hypotension was too small to evaluate adequately its association with positive affect. When individual PANAS items were examined for associations with hypotension, significant differences (P<0.05) were found for Interested, Strong, Enthusiastic, Inspired, Determined and Attentive between subjects with diastolic hypotension and those with normal diastolic blood pressure.
Table 1 Mean (and 95% CI) values for depression, anxiety, positive affect and negative affect for hypotensive, normotensive and hypertensive groups
| Measure | Diastolic hypotensive | Diastolic normotensive | Diastolic hypertensive | P 1 |
| (n=104-120) | (n=98-111) | (n=94-104) | ||
| Depression | 2.35 (1.98-2.71) | 1.89 (1.44-2.16) | 1.99 (1.65-2.32) | 0.087 |
| Anxiety | 2.39 (2.02-2.76) | 2.20 (1.81-2.59) | 2.21 (1.82-2.60) | 0.738 |
| Positive affect | 29.90 (28.65-31.16) | 33.12 (31.96-34.27) | 32.75 (31.54-33.96) | 0.0002 |
| Negative affect | 17.19 (15.94-18.45) | 16.95 (15.70-18.21) | 18.19 (16.74-19.63) | 0.389 |
| Systolic hypotensive | Systolic normotensive | Systolic hypertensive | ||
| (n=31-37) | (n=68-80) | (n=196-222) | ||
| Depression | 2.29 (1.70-2.87) | 1.99 (1.56-2.43) | 2.03 (1.78-2.29) | 0.724 |
| Anxiety | 2.35 (1.66-3.04) | 2.11 (1.69-2.54) | 2.32 (2.04-2.59) | 0.727 |
| Positive affect | 31.53 (29.46-33.61) | 30.34 (28.81-31.87) | 32.46 (31.59-33.33) | 0.0496 |
| Negative affect | 17.30 (14.51-20.09) | 16.39 (15.03-17.75) | 17.82 (16.87-18.77) | 0.304 |
To control for possible confounders, a multiple linear regression analysis was carried out to predict the positive affect from hypotension, hypertension, use of antihypertensive medication, age, gender, education, marital status and a range of physical health and cognitive measures (see Reference Korten, Jorm and JiaoKorten et al, 1999, for details). Controlling for these factors, positive affect was related to diastolic hypotension (unstandardised β= ‒2.18, P=0.031) and the use of antihypertensive medication (β=-2.61, P=0.004). Antihypertensive medication was being taken by 39% of the sample. Among those on medication, 24% had diastolic hypotension and 5% had systolic hypotension.
DISCUSSION
Diastolic hypotension was associated with lower positive affect but not with higher negative affect. The weak and inconsistent associations of hypotension with depression in the literature could be because depression measures are correlated more strongly with negative affect than with low positive affect.
Effect of antihypertensive medication
Diastolic hypotension was found in a quarter of users of antihypertensive medication, suggesting that treatment might be leading to hypotension in some cases. Furthermore, the use of antihypertensive medication was found to be associated with low positive affect when blood pressure status was statistically controlled. As previous studies have done, we defined hypotension based on a single measurement occasion (although measured twice), which would have involved some unreliability. Whether or not a participant uses anti-hypertensive medication may be an independent predictor because it gives additional reliable information about blood pressure status. Unfortunately, we did not collect data on type of medication, so we could not explore whether the association is a general one or specific to particular classes of medication.
Limitations
Other limitations of this study must be acknowledged. A cross-sectional study such as this one cannot distinguish whether hypotension is a cause or effect of low positive affect, or whether there is a common cause of both. Although the present study had longitudinal data on blood pressure, positive affect was measured only at Wave 3. Another limitation is that the use of psychotropic medication, which is another potential confounding variable, was not measured. The association of hypotension with lower positive affect requires further research in longitudinal studies and in controlled trials of antihypertensive treatment.
Clinical Implications and Limitations
CLINICAL IMPLICATIONS
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▪ Hypotension may be associated with lowered positive affect, which is a feature of depression.
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▪ Antihypertensive medication may lead to hypotension and lower positive affect.
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▪ Hypotension is not associated with increased negative affect, which is a feature common to both anxiety and depression.
LIMITATIONS
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▪ Small numbers did not allow a reliable assessment of the association of systolic hypotension with positive affect.
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▪ Blood pressure was measured only on a single occasion.
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▪ Information on the type of antihypertensive medication and on the use of psychotropic medication was not collected.
ACKNOWLEDGEMENTS
Ailsa Korten, Helen Christensen, Scott Henderson, Patricia Jacomb and Bryan Rodgers were co-investigators on this study. Help in various phases of the study was provided by Suzanne Dee, Colleen Doyle, Susan Lindsay, Karen Maxwell and Ruth Scott.
eLetters
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