Increasing Role of Overweight/Obesity as the Determinant of Hypertension and the Consequent Cardiovascular Diseases in Japan

See article vol. 30: 335-347

Overweight/obesity is a determinant of hypertension, together with high sodium and alcohol intake or low physical activity¹⁾. It was reported that hypertension without being overweight used to constitute a majority of the hypertension cases in Japanese rural communities in 1960’s but not in 1980’s²⁾. This change was accompanied by increases in overweight/obesity and the proportion of hypertension among the overweight/obesity^{2, 3)}. Even after 1980’s, increase in the attribute of overweight/obesity to hypertension has been reported in Japan or China^{4, 5)}. Since hypertension continues to be the leading risk factor for cardiovascular diseases (CVDs) with or without overweigh/obesity⁶⁾, increases in the prevalence of overweight/obesity and the fraction of hypertension attributable to overweight/obesity suggest an increasing role of overweight/obesity in determining the magnitude of CVD risk.

In this issue of the journal, Matsumura et al. reported that the prevalence of body mass index (BMI) ≥ 25.0 kg/m² increased, and the association of BMI ≥ 25.0 kg/m² compared to BMI 23.0–＜25.0 kg/m² with the incidence of CVD became stronger from 1963–1969 to 2000–2005 (Fig.1)⁷⁾. As a result and expectedly, the population-attributable fraction of BMI ≥ 25.0 kg/m² for the CVD incidence in reference to BMI 23.0–＜25.0 kg/m² significantly increased, especially in 1990–1999 and 2000–2005 cohorts. The study also revealed that the significant associations of BMI ≥ 25.0 kg/m² with CVD observed in 1990–1999 and 2000–2005 cohorts were mostly mediated by concomitant increase in systolic blood pressure and the proportion of antihypertensive medication use, which also confirmed the role of overweight/obesity as the determinant of hypertension.

Fig.1. Changes in the prevalence of overweight/obesity defined as body mass index (BMI) ≥ 25.0 kg/m² (blue solid bar, left side vertical axis) and its population attributable fractions (PAFs, orange shaded bar, left side vertical axis) and hazard ratios (HRs, right side vertical axis) for the incidence of cardiovascular diseases (CVDs) in four communities in Japan, 1963–2019.

Dashed line indicates HRs of overweight/obesity for CVD incidence after adjustment for mediators, including hypertension (mediation effect removed HRs). The figure was created by the author using data presented in Matsumura T, et al.⁷⁾

The authors also showed that average systolic blood pressure decreased overtime, but that seems more apparent in the BMI ＜21.0 kg/m² group than in the BMI ≥ 25.0 kg/m² (Fig.2). The proportion of individuals with antihypertensive medication use significantly increased, especially in BMI ≥ 25.0 kg/m². These findings confirmed that existing differences in systolic blood pressure and the level of other mediators according to the different degree of overweight/obesity, which explains increased CVD risk of overweight/obesity, need to be reduced^{8, 9)}. The most straightforward strategy would be to control or prevent overweight/obesity, but other ways, including appropriate medical control of the risk factors in overweight/obese individuals, are also warranted.

Fig.2. Changes in the proportions of individuals with antihypertensive medication use (HT med use) in two body mass index (BMI) strata (＜21.0 kg/m², dark shaded bar and 25.0 kg/m², light shaded bar, both at right side vertical axis), and the average systolic blood pressure (Ave. SBP, mmHg) in the same BMI strata (＜21.0 kg/m², orange dashed line and 25.0 kg/m², yellow solid line, both at left side vertical axis) in four communities in Japan, 1963–2019.

The figure was created by the author using data presented in Matsumura T, et al.⁷⁾

Conflicts of Interest

None.

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