What is the clinical evidence from this study?

Study design: Cohort. Population: Stroke (n=11404). Intervention: Body mass index (BMI) vs. BMI 22.0-24.9 kg/m2. Primary outcome: All-stroke incidence (HR 2.11, 95% CI 1.17-3.82).

What does this research mean for the field?

Low BMI (≤18.5 kg/m2) in men and high BMI (≥30.0 kg/m2) in women are associated with a significantly increased risk of all-stroke compared to a normal BMI of 22.0-24.9 kg/m2 in Japanese community residents. Novelty: ClaimNovelty.CONTRADICTORY. Consensus alignment: ConsensusAlignment.CHALLENGES_CONSENSUS.

March 7, 2017Open Access

Body mass index and stroke incidence in Japanese community residents: The Jichi Medical School (JMS) Cohort Study

NKNami KawateSaitama Prefectural University KKKazunori KayabaSaitama Prefectural University MHMotohiko HaraTeikyo University

Key Result

Low BMI (≤18.5 kg/m2) in men (HR 2.11) and high BMI (≥30.0 kg/m2) in women (HR 2.25) were associated with a significantly increased risk of all-stroke compared to a BMI of 22.0-24.9 kg/m2.

Study Design

Type

Cohort (n=11,404)

Multicenter

Yes

Structured PICO

Does BMI category affect the incidence of stroke in Japanese community residents?

Population

12,490 Japanese community residents from the Jichi Medical School Cohort Study

Intervention

BMI categories (≤18.5, 18.6–21.9, 25.0–29.9, and ≥30.0 kg/m2)

Comparator

BMI of 22.0–24.9 kg/m2

Outcome

Stroke incidence (all-stroke, cerebral infarction, cerebral hemorrhage) over mean 10.8 years follow-uphard clinical

In a Japanese cohort, low BMI was a risk factor for stroke in men, while high BMI was a risk factor for stroke in women.

Main Result

Effect estimate: HR 2.11 (95% CI 1.17-3.82)

Limitations

Participants were not randomized and appeared healthier than the general population
Smoking status, alcohol drinking status, and history of medication were self-reported
Participants were weighed with their clothes on
Cases involving asymptomatic stroke were not included, potentially underestimating incidence
Significant findings were based on a small number of incident stroke cases (11 in lean men, 13 in obese women)

Abstract

High body mass index (BMI) has been reported as a risk factor for cardiovascular events in Western countries, while low BMI has been reported as a risk factor for cardiovascular death in Asian countries, including Japan. Although stroke is a major cause of death and disability in Japan, few cohort studies have examined the association between BMI and stroke incidence in Japan. This study aimed to examine the association between BMI and stroke incidence using prospective data from Japanese community residents. Data were analyzed from 12,490 participants in the Jichi Medical School Cohort Study. Participants were categorized into five BMI groups: ≤18.5, 18.6–21.9, 22.0–24.9, 25.0–29.9, and ≥30.0 kg/m2. Multivariate-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using the Cox proportional hazard model. The group with a BMI of 22.0–24.9 kg/m2 was used as the reference category. During mean follow-up of 10.8 years, 395 participants (207 men and 188 women) experienced stroke, including 249 cerebral infarctions and 92 cerebral hemorrhages. Men with a BMI ≤18.5 kg/m2 (HR 2.11; 95% CI, 1.17–3.82) and women with a BMI ≥30.0 kg/m2 (HR 2.25; 95% CI, 1.28–5.08) were at significantly higher risk for all-stroke. Men with a BMI ≤18.5 kg/m2 were at significantly higher risk for cerebral infarction (HR 2.15; 95% CI, 1.07–4.33). The association between BMI and stroke incidence observed in this population was different than those previously reported: low BMI was a risk factor for all-stroke and cerebral infarction in men, while high BMI was a risk factor for all-stroke in women.

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