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29-01-2012 | Cardiology | Article

Hypertension major risk factor for mortality in Japan


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MedWire News: High blood pressure (BP) and tobacco smoking are the two major risk factors for adult mortality from noncommunicable diseases and injuries in Japan, researchers say.

Further investigation through national health surveys will help understand factors that contribute to the inadequate control of BP in the Japanese population, report Nayu Ikeda (University of Tokyo, Japan) and co-workers in PLoS Medicine.

They obtained data on exposure to 16 risk factors from the National Health and Nutrition Surveys and epidemiologic studies, as well as data on the number of cause-specific deaths using vital records, and relative risks from epidemiologic studies and meta-analyses.

The 16 risk factors studied were high blood glucose, high levels of low-density lipoprotein (LDL) cholesterol, high BP, overweight/obesity, alcohol use, tobacco smoking, physical inactivity, high dietary trans fatty acids, low dietary polyunsaturated fatty acids, high dietary salt, low intake of fruit and vegetables, hepatitis B virus, hepatitis C virus, Helicobacter pylori bacterium, human papillomavirus, and human T-lymphotropic virus type 1.

The researchers then applied a comparative risk assessment framework to estimate the effects of excess risks on deaths and life expectancy at the age of 40 years.

In 2007, tobacco smoking and high BP accounted for around 129,000 deaths and 104,000 deaths, respectively, followed by physical inactivity at 52,000 deaths, high blood glucose at 34,000 deaths, high dietary salt intake at 34,000 deaths, and alcohol use at 31,000 deaths.

High BP was the greatest risk factor for cardiovascular mortality of all the risk factors studied, note the authors.

Analysis using theoretical minimum-risk exposure distribution revealed that life expectancy at the age of 40 years in 2007 would have been extended by 1.4 years for men and women if exposure to multiple cardiovascular risk factors (defined as high body mass index [BMI], BP, blood glucose, and LDL cholesterol) had been reduced to their optimal levels (21 kg/m2, 115 mmHg systolic, 4.9 mmol/L, and 2.0 mmol/L, respectively, as defined by the authors).

If exposure to multiple cardiovascular risk factors had been reduced to national guideline definitions (BMI: 22 kg/m2, systolic BP: 130 mmHg, blood glucose: 5.6 mmol/L, LDL cholesterol: 3.1 mmol/L), life expectancy at the age of 40 years would have increased by only 0.7 years, and by 0.4 years through reduced systolic blood pressure alone.

Stroke deaths due to high BP consistently declined over time for both genders under 80 years of age. This favorable trend continued into the 2000s for both genders under the age of 60 years, but ceased for men aged 70-79 years by the mid 1990s.

"Potential key factors for the decline of BP in the Japanese population may include increased use of BP-lowering drugs among patients with hypertension and a reduction in dietary salt intake," hypothesize the authors.

"These successes may be attributed to the support of the national government for community-based programs for hypertension control that were proven to be effective in pilot studies conducted in the 1960s and 1970s," they add.

Ikeda and team point out that because the traditional Japanese diet is high in salt, which is present in soy sauce, miso soup, and salted vegetables and fish, it is "essential" that extra effort is made by the food industry to reduce sodium content in commercially processed foods.

They conclude: "It is urgent to establish a monitoring system for management of high BP at the national level."

MedWire ( is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2012

By Piriya Mahendra

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