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Diagnosis and control of hypertension in the elderly populations of Japan and the United States

1. Introduction

Studies conducted throughout the world have shown that prolonged hypertension leads to
an increased risk of heart disease, stroke, kidney disease, and death (Benetos, Safar, Rud-
nichi et al., 1997; Coresh, Selvin, Steven et al., 2007; Digiovanna, 1999; Franklin, Larson,

Khan et al., 2001; MacMahon, Peto, Cutler et al., 1990). Hypertension is one of the major
controllable risk factors for poor health outcomes in old age. The number of older persons
around the world using medication to lower blood pressure is growing. National differ-
ences in the effectiveness of hypertension diagnosis and treatment should relate to overall
differences in population health and mortality. Japan is a world leader in life expectancy
while the United States (US) lags behind Japan and many other advanced countries. These
differences lead to questions about how Japan does so well in promoting long life and why
the United States does so poorly. It has been suggested that Japan’s public health empha-
sizing on hypertension treatment has been an important factor in reducing stroke mortality
and raising life expectancy (Murray, 2011). A detailed comparison of how hypertension
diagnosis, treatment, and control differ between the two countries could provide some in-
sights into overall health differences. Furthermore, the diagnosis and the control of hyper-
tension among the elderly provide insights into the overall quality of national health care
systems in caring for their elderly populations.
Paradoxically, the incidence of hypertension in Japan is known to be relatively high;
while that in the US is relatively low (Crimmins, Vasunilashorn, Kim et al., 2008; Marmot,
Syme, Kagan et al., 1975; Crimmins, Garcia, and Kim, 2010). National levels of hyper-
tension may reflect differences in culture, social factors, epidemiological history, and
health care policies as well differences in various dietary styles and genetic components at
individual level. One important factor in national differences in the prevalence of high
blood pressure is the use of antihypertensive medication which has resulted in lowered
levels of hypertension among older persons in Japan and in the U.S. (Ikeda, Gakidou, Ha-
segawa et al., 2008). Antihypertensive medication usage increased earlier and remains
higher in the U.S. than Japan (Crimmins, Garcia, Kim et al., 2010; Ikeda, Gakidou, Hase-
gawa et al., 2008).
This study is unique in using individual level data from two nationally-representative
studies to examine hypertension among those 68 years of age and older in the U.S. and
Japan. Many studies of hypertension are based on local or regional samples and are not
representative of the entire country. In addition, this study utilizes both self-report and
measured blood pressure so that a more complete picture of hypertension in the elderly
population is provided. This results from the comparisons not only of measured high blood
pressure but also of undiagnosed, controlled and uncontrolled high blood pressure. This is
possible because measured blood pressure has recently been added to the U.S. Health and
Retirement Study (HRS) and the Nihon University Japanese Longitudinal Study of Aging
(NUJLSOA), providing an opportunity for a comparative analysis between national sam-
ples of these two countries. These longitudinal studies already included self-reports of
hypertension and use of antihypertensives. This is the first cross-national comparison us-
ing measured blood pressure indicators based on individual level data for these two coun-
tries. This allows us to examine the associations between demographic factors and the
prevalence, diagnosis, and control of hypertension in the two countries.
The questions that will be addressed in this paper are: (i) how do levels of overall
hypertension, and diagnosed and undiagnosed hypertension differ among older persons in
Japan and the U.S.; (ii) how does antihypertensive medication use and control of hyper-
tension differ by country; and (iii) how are these measures of hypertension and control of
hypertension associated with measured systolic blood pressure.

International Journal of Population Studies | 2015, Volume 1, Issue 1 20