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Reducing cardiovascular mortality through lifestyle change in Japan

Andrew Mente, Salim Yusuf
DOI: http://dx.doi.org/10.1093/eurheartj/ehr446 428-429 First published online: 14 February 2012

This editorial refers to ‘Healthy lifestyle behaviours and cardiovascular mortality among Japanese men and women: the Japan collaborative cohort study’, by E. Eguchi et al., on page 467

Following the Second World War, Japan experienced spectacular economic growth as the country became the world's second largest economy. In parallel, rates of cardiovascular disease (CVD) in Japan increased steadily for several decades as the population became exposed to a westernized lifestyle. Despite these changes, heart disease rates in Japan, China, Korea, and Taiwan are still substantially lower than those in North America, whereas stroke rates are several fold higher.1 Moreover, Japanese migrants to the USA display a three- to six-fold rise in mortality from heart disease, but the stroke mortality rate of these migrant groups is one-fifth of that in Asia. This paradoxical pattern of CVD between Japanese who are exposed to ‘western’ lifestyles while living in Japan vs. those living in the USA is intriguing and suggests that the ‘westernizing’ influences in each setting were quite different and produced variable effects. The average blood pressure level at specific levels of body mass index (BMI) in Japan is markedly higher than in US whites in all age–sex groups.2 There are continental differences in micronutrient intake that may explain the differences in blood pressure and stroke rates between these regions. In East Asian communities compared with those in North America, the mean daily intake of potassium, calcium, phosphorus, and, to a lesser extent, magnesium, is substantially lower, while sodium intake is higher.3 On the other hand, the substantially lower death rate from ischaemic heart disease in Japan has been attributed to a higher polyunsaturated/saturated fat ratio, higher omega-3 fatty acids, higher soy proteins, and lower stress. In fact, fish consumption in Japan is still among the highest in the world and the average omega-3 intake of 1 g a day is about eight times higher than the amount the typical American consumes.4 Conversely, North Americans consume more calories, total fat, saturated and trans fatty acids, as well as refined sugar, and less total carbohydrates and starch compared with East Asians.3 Smoking rates among Japanese men, however, are more than three times those observed in North America. The rapid changes in CVD rates in migrant studies demonstrate the potent effects of changing lifestyle on CVD risk in populations.

Eguchi and colleagues have reported that in healthy Japanese men and women aged 40–79 years without a history of CVD at baseline, greater adherence to a healthy lifestyle is associated with a two-thirds lower mortality from stroke, coronary heart disease (CHD), and CVD in men, and a three-quarters reduction in women.5 These findings suggest that a large fraction of the current burden of CVD in Japan is preventable through lifestyle modification. The findings are in keeping with previous prospective cohort studies in the USA and Europe, which showed that adherence to a healthy lifestyle is associated with dramatically lower CVD mortality (i.e. relative risk reductions >70% in the highest adherers to a healthy lifestyle compared with the lowest).6,7 The study by Eguchi et al. extends these observations to an Asian population outside North America and Europe, and suggests that a healthful lifestyle can be defined to be about the same across different geographic regions. These results are also compatible with the key finding of the INTERHEART study which showed that lifestyle factors (smoking, diet, and physical activity) accounted for about half of the population-attributable risk of myocardial infarction.

The study is also noteworthy for its consideration of two non-traditional lifestyle measures in the adherence score: milk intake and sleep duration. Epidemiological data reveal that the consumption of a low calcium diet is associated with a higher mean population blood pressure and increased prevalence of hypertension.8 In the original DASH trial, the diet that emphasized dairy products in addition to fruit and vegetables lowered blood pressure significantly and more dramatically than either the so-called ‘fruit/vegetable’ diet or the ‘control’ diet. There is previous evidence that sodium sensitivity is observed preferentially in people with low calcium intakes.9 Evidence has also been mounting that a diet rich in dairy products is associated with a lower risk of glucose intolerance, type 2 diabetes, and the metabolic syndrome.10 Lack of sleep has also been associated with increased blood pressure as well as cholesterol levels.11 During periods of sleep deficiency, the body enters a state of stress which triggers an increase in blood pressure and production of stress hormones. The increase in stress hormones in turn raises inflammation, which is associated with increased CVD risk, as well as risk of cancer and diabetes. There is also evidence that <7 h of sleep is associated with being overweight or obese.12 It is believed that reduced sleep impacts the balance of hormones that affect appetite. The hormones ghrelin and leptin, important for the regulation of appetite, have been found to be disrupted by reduction in sleep.12

These findings have some clear implications for public health in Japan and many other countries in Asia. Foremost, the healthful behaviours outlined by Eguchi et al. are not extreme. For example, the fruit criterion could be met by having at least one serving per day; physical activity by an hour of walking daily or exercise 5 h weekly; and sleep duration of 5.5–7.5 h daily. Thus moderate changes in behaviour can result in reductions in risk. These findings lend support to the notion of creating policies and the environment for people to be able to make these moderate changes. Additionally, given the emerging observational data showing the health benefits of dairy product intake, the present findings have implications for increasing dairy consumption in these populations in a culturally sensitive fashion. Importantly, since smoking cessation is an important lifestyle change, government restrictions on tobacco items are warranted. For example, it is known that increasing the taxation on cigarettes has a real effect on the consumption of tobacco.13 In addition, there is a need for education campaigns, banning of advertising of cigarettes, and of course restricting the sale and access to cigarettes are also very important. Stronger measures than are currently taken are needed in Japan, as smoking rates among Japanese men are more than three times higher than those seen in North America.

It is noteworthy that the lifestyle changes outlined in this study are unlikely to impact CVD incidence in the short term (i.e.1–2 years), but could well have large and important effects in the long term. On the one hand, ecological data have shown that changes in national CVD rates track with the changes in health behaviours. In Finland, for instance, CHD mortality rates declined by 63% between 1982 and 1997, with about two-thirds of the decline in mortality attributable to reduction in or control of major risk factors (smoking, cholesterol, and blood pressure), mainly resulting from energetic and comprehensive prevention policies over many decades including promotion of more healthy diets.14 In contrast, CVD mortality in Beijing increased substantially in parallel with worsening CVD risk factors (smoking, cholesterol, obesity, and diabetes), reflecting an increasingly ‘western’ diet.15 However randomized trials of multiple risk factor interventions collectively have failed to show large reductions in CVD mortality.16 There are two apparent reasons for this. First, since long-term lifestyle interventions are less amenable to study in trials, investigators have relied on short-term trials (i.e. <2 years) and examined intermediate surrogate outcomes. However, these trials cannot detect plausible reductions in clinical outcomes. Secondly, in the few long-term trials, the degree to which diet and lifestyle are changed has been modest, which in turn would be expected to produce small changes in risk factors and clinical outcomes. For instance, in the Women's Health Initiative trial, there was no material benefit in consuming a low-fat diet against CVD mortality after 8 years, mainly due to poor long-term compliance with the prescribed diet. (An apparent exception was the Lyon Diet Heart Study, which showed a 79% reduction in CHD events with a ‘Mediterranean diet’, though the findings have not been replicated, nor have the data been independently verified.) Thus, not surprisingly, the clinical trial data have limitations. Therefore, the benefits from dietary and behaviour modification may take many decades to manifest. This delayed benefit of lifestyle change was clearly demonstrated in the Multiple Risk Factor Intervention Trial which showed that the lifestyle intervention produced little benefit (7.1%) at 5 years, but a larger reduction in CHD events after the extended follow-up (11.4%) after 16 years. Such a relative risk reduction is consistent with the modest impact on risk factors during the intervention phase.

In summary, the effects of lifestyle change on CVD risk reduction can be important, consistent, and universal. An effective multicomponent lifestyle change strategy is likely to lower the CVD burden substantially in Japan and in other Asian countries in the long term.

Conflict of interest: none declared