RESEARCH - Hypertension associated with fewer musculoskeletal complaints

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Hypertension associated with fewer musculoskeletal complaints

Rheumawire

Apr 26, 2005

Zosia Chustecka

Trondheim, Norway - Patients with high blood pressure (BP) have fewer

chronic musculoskeletal complaints (MSCs) than those with normal blood

pressure, a large-scale population study has found [1]. One explanation for

the finding is the phenomenon of hypertension-related hyperalgesia, due to

an interaction between the cardiovascular and pain regulatory systems, say

the researchers.

The findings, reported in the April 25, 2005 Archives of Internal Medicine,

are " remarkably consistent, " say the authors, Dr Knut Hagen and colleagues

(Norwegian University of Science and Technology, Trondheim). High systolic

(SBP) or diastolic blood pressure (DBP) was associated with a 10% to 60%

lower prevalence of musculoskeletal complaints, and there was a strong

linear trend (p<0.001) of decreasing prevalence with increasing BP values.

The inverse relationship held across all age groups, both sexes, and all 10

anatomical sites at which patients reported feeling pain continuously for at

least 3 months in the past year.

Asked to comment on this study, Dr Louis Bridges (University of Alabama,

Birmingham), who acts as an editorial consultant for jointandbone.org, said:

" This is an interesting finding. I had not previously been aware of the

reports of inverse association between musculoskeletal complaints and

hypertension. The data look solid, but the explanation is unknown. Because

there is no obvious pathogenetic link between blood pressure and chronic

musculoskeletal pain, I worry that there are unknown confounding factors

that may make this finding difficult to replicate in future studies. On the

other hand, if a pathogenetic link between BP and musculoskeletal pain were

subsequently found, it would lead to a significant paradigm shift. "

" At the present time, I do not think that this will change a

rheumatologist's approach to treating patients with musculoskeletal

complaints, " Bridges tells rheumawire. Lead author of the new study Hagen

agrees: " Our findings do not have direct implications for the clinical

treatment of patients or for rheumatologists or for other doctors treating

patients with pain. "

Hagen thinks the new findings will come as a surprise to many physicians. He

tells rheumawire: " I do not think that rheumatologists are aware of such

inverse association between BP and chronic MSCs, and our findings give

interesting clues for further knowledge of important pain mechanisms in the

central nervous system. However, how antihypertensive drugs influence these

pain mechanisms must be evaluated further in other studies with different

study design. "

First large-scale population study

Hagen et al comment that, to their knowledge, this is the first large-scale

population-based study to investigate the relationship between BP and

chronic MSCs at various anatomical sites. They analyzed data from 2

consecutive public-health studies, running from 1984 to 1986 (Nord-Trondelag

Health Study, HUNT-1) and from 1995 to 1997 (HUNT-2). A total of 46 901

adults participated in both studies.

Both studies measured BP, but only HUNT-2 included questions about MSCs.

Just over half of the participants (51.4%, n=24 127) reported that they had

experienced pain and/or stiffness in muscle and joints continuously for at

least 3 months in the past year. These individuals were categorized as

having chronic MSCs and were asked to mark the location of the pain on a

diagram (eg, neck, shoulders, lower back, ankle/foot, etc).

The prevalence of chronic MSCs was estimated using multiple logistic

regression. A high systolic BP (SBP >150 mm Hg) measured in the HUNT-1 study

was associated with a lower prevalence of chronic MSCs in the HUNT-2 study

in all age groups and for each sex. The prevalence of chronic MSCs was 20%

to 60% lower at all 10 anatomical locations. The inverse relationship was

most marked for pain in the trunk (back, chest, abdomen) but was not

significantly different from pain elsewhere, the group reports.

The decrease in prevalence of chronic MSCs with increasing systolic BP was

almost linear, the researchers comment, and the inverse relationship was

seen both in individuals who were taking antihypertensive medication as well

as those who were not. However, the highest prevalence of chronic MSCs was

found among individuals with a low systolic BP and current use of

antihypertensives, and this tendency was present even after adjusting for a

significant age difference.

The researchers comment that their results suggest that the use of

antihypertensives may modify the relationship between hypertension and

chronic MSCs, so that those with treated hypertension experience more pain

that those in whom it remains untreated. For example, in women with high SBP

in HUNT-2, the prevalence of chronic MSCs was higher among those taking

antihypertensive agents than among those who were not taking these drugs

(prevalence odds ratio 0.82 vs 0.67). They note that a previous study has

reported that patients with hypertension report an increase in pain

sensitivity during treatment with antihypertensive medication [2].

The findings for diastolic blood pressure showed parallel trends. The

prevalence of chronic MSCs tended to be highest among individuals with a low

DBP and current use of antihypertensive agents, but no significant

interaction was found between the use of these drugs and DBP in relationship

to chronic MSCs.

Less pain because visiting doctors more often?

One simple explanation for the findings could be that the patients with

hypertension visited doctors more often and so had all their symptoms better

treated than the normotensive individuals. However, this is unlikely, say

Hagen et al, because a consistent dose-response relationship was clearly

demonstrated among those without the use of antihypertensive medication.

The fact that pain was lower at all 10 anatomical sites, where different

local mechanisms are involved, suggests a fundamental relationship between

BP and pain perception in the central nervous system, the researchers write.

Of particular relevance is the finding that the inverse relationship between

the 2 extends even into the normotensive range, they add: this suggests that

it may reflect some common central mechanism underlying antinociception and

cardiovascular regulation rather than a specific effect of hypertension

itself.

The findings may have important consequences, Hagen et al the researchers

comment. As BP had a relatively strong association with chronic MSCs, it

could be an important confounding factor in clinical trials and so should be

adjusted for. And as antihypertensive medications are so widely used, there

should be further study of how they influence pain sensitivity, and

individuals in pain should be monitored when they start such therapy.

Sources

1. Hagen K, Zwart JA Holmen, et al. Does hypertension protect

against chronic musculoskeletal complaints? The Nord-Trondelag Health Study.

Arch Intern Med 2005; 165:916-922.

2. Guasti L, Zanotta D, Diolisi A, et al. Changes in pain

perception during treatment with angiotensin-converting enzyme inhibitors

and angiotensin-II typesi 1 receptor blockade. J Hypertens 2002; 20:485-491.

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