What is the clinical evidence from this study?

Study design: Cohort. Population: Chronic mental stress and blood pressure (n=1673). Intervention: Chronic mental stress vs. Low mental stress. Primary outcome: Average resting systolic blood pressure (p=0.002).

What does this research mean for the field?

Chronic mental stress has a directly proportional association with systolic and diastolic blood pressure in obese men, but an inversely proportional association in lean men, indicating that body mass index modifies this relationship. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

January 1, 2014Open Access

Body Mass Index-Modified Relationship of Chronic Mental Stress With Resting Blood Pressure During 5 Years in Japanese Middle-Aged Male Workers

Key Result

Chronic mental stress showed a directly proportional association with systolic and diastolic blood pressure in obese men (P=0.001) but an inversely proportional association in lean men.

Study Design

Type

Cohort (n=1,673)

Multicenter

Structured PICO

Does body mass index modify the relationship between chronic mental stress and resting blood pressure in middle-aged men?

Population

1,673 Japanese middle-aged male local government employees not taking antihypertensive drugs and with no history of cardiovascular disease

Intervention

Chronic mental stress (assessed by questionnaire)

Outcome

Averages and changes of resting systolic and diastolic blood pressures over 5 yearssurrogate

BMI modifies the relationship between chronic mental stress and resting blood pressure, with stress increasing BP in obese individuals but potentially lowering it in lean individuals.

Main Result

p-value: p=0.002

Limitations

Subjects analyzed were narrowed down to 38% of the target population
Subjects taking antihypertensive drugs were excluded, limiting applicability to those with moderate to severe hypertension
Tranquilizer usage was not checked
Ambulatory BP was not measured
The lower BP of two measurements was adopted for those who presented with high BP initially
Levels of stress and BMI were assessed statically rather than dynamically over the 5 years
Cross-sectional analyses leave causality unsolved
No female subjects were included

Abstract

BACKGROUND: Chronic mental stress has been reported to be directly or inversely proportional to blood pressure (BP). To explain this inconsistent relationship, we assumed effect-modification by body mass index (BMI). METHODS AND RESULTS: We examined 1,673 Japanese male local government employees who were not taking antihypertensive drugs or had no history of cardiovascular disease. BP and BMI were recorded at yearly health checkups. Exposure to mental stress, smoking, drinking, exercising, and salty taste were checked by questionnaire in 1997 and 2002. The main effect and interaction of stress and BMI on the averages and changes of resting systolic and diastolic BPs over the 5 years were assessed by a general linear model by adjusting for confounders. Obesity (BMI ≥25kg/m(2)) was significantly related with higher average systolic and diastolic BPs (P<0.001, P<0.001, respectively), whereas mental stress was not, showing a significantly different relationship dependent on BMI (P for interaction =0.002, 0.004): a significant and directly proportional association with systolic and diastolic BPs (P=0.001, 0.001) in the obese, but borderline significant and inversely proportional association (P=0.07, 0.08) in the lean. Only BMI was significantly related to the degree of BP change. CONCLUSIONS: Whereas BMI was proportionally associated with BP, BMI was a modifier which, depending on its level, inverted the direction of the association between chronic mental stress and resting BP.

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