Akira Okayama

Dr. Akira Okayama

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Research Focus & Metrics

Academic Career Length

23Years (2004-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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5 January 2019 in Environmental Health and Preventive Medicine
Verified
Journal Article
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MNMieko Nakamura
Mieko Nakamura
Toshiyuki OjimaToshiyuki Ojima
Toshiyuki Ojima
TNTomomi Nagahata
Tomomi Nagahata
IKImako Kondo
Imako Kondo
TNToshiharu Ninomiya
Toshiharu Ninomiya
KMKatsuyuki Miura
Katsuyuki Miura
Oral health is thought to be associated with diet quality, and socioeconomic status (SES) affects both oral health and diet. The aim of this study was to investigate the association between the number of teeth and dietary intake as well as nutritional biomarker, considering the subjects’ SES. We conducted a cross-sectional analysis of data from 2049 individuals aged ≥ 50 years from the National Integrated Project for Prospective Observation of Non-communicable Disease and its Trends in the Aged 2010. The number of remaining teeth was categorized into age-specific quartiles (Q1 to Q4). We assessed the adjusted means and 95% confidence intervals for dietary variables by the number of teeth using analysis of covariance. Stratified analyses by SES were also conducted. The intake of grain products was 31 g higher, and those of vegetables and meat were 30 g and 8 g lower, respectively, in Q1 (fewer teeth) than in Q4 (more teeth). Carbohydrate intake was higher whereas protein, minerals (potassium, magnesium, and zinc), vitamins (vitamins A, E, B1, B6, β-carotene, and folic acid), and dietary fiber intakes were lower among individuals with fewer teeth. Adjusted mean serum albumin levels were low in Q1. The associations between the number of teeth and dietary intake were more evident in individuals with a low SES. Having few remaining teeth was associated with a low nutrient intake and low serum albumin levels in middle-aged and older Japanese adults, and these associations were more evident in individuals with low SES.

13 July 2016 in BMJ Open
Verified
Journal Article
Open access
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AOAkira Okayama
Akira Okayama
NONagako Okuda
Nagako Okuda
KMKatsuyuki Miura
Katsuyuki Miura
Tomonori OkamuraTomonori Okamura
Tomonori Okamura
THTakehito Hayakawa
Takehito Hayakawa
HUHirotsugu Ueshima
Hirotsugu Ueshima
Objectives To evaluate the impact of dietary sodium and potassium (Na–K) ratio on mortality from total and subtypes of stroke, cardiovascular disease (CVD) and all causes, using 24-year follow-up data of a representative sample of the Japanese population. Setting Prospective cohort study. Participants In the 1980 National Cardiovascular Survey, participants were followed for 24 years (NIPPON DATA80, National Integrated Project for Prospective Observation of Non-communicable Disease And its Trends in the Aged). Men and women aged 30–79 years without hypertensive treatment, history of stroke or acute myocardial infarction (n=8283) were divided into quintiles according to dietary Na–K ratio assessed by a 3-day weighing dietary record at baseline. Age-adjusted and multivariable-adjusted HRs were calculated using the Mantel-Haenszel method and Cox proportional hazards model. Primary outcome measures Mortality from total and subtypes of stroke, CVD and all causes. Results A total of 1938 deaths from all causes were observed over 176 926 person-years. Na–K ratio was significantly and non-linearly related to mortality from all stroke (p=0.002), CVD (p=0.005) and total mortality (p=0.001). For stroke subtypes, mortality from haemorrhagic stroke was positively related to Na–K ratio (p=0.024). Similar relationships were observed for men and women. The observed relationships remained significant after adjustment for other risk factors. Quadratic non-linear multivariable-adjusted HRs (95% CI) in the highest quintile versus the lowest quintile of Na–K ratio were 1.42 (1.07 to 1.90) for ischaemic stroke, 1.57 (1.05 to 2.34) for haemorrhagic stroke, 1.43 (1.17 to 1.76) for all stroke, 1.39 (1.20 to 1.61) for CVD and 1.16 (1.06 to 1.27) for all-cause mortality. Conclusions Dietary Na–K ratio assessed by a 3-day weighing dietary record was a significant risk factor for mortality from haemorrhagic stroke, all stroke, CVD and all causes among a Japanese population.

1 January 2018 in Journal of Epidemiology
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Journal Article
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AKAya Kadota
Aya Kadota
NONagako Okuda
Nagako Okuda
TOTakayoshi Ohkubo
Takayoshi Ohkubo
Tomonori OkamuraTomonori Okamura
Tomonori Okamura
NNNobuo Nishi
Nobuo Nishi
KMKatsuyuki Miura
Katsuyuki Miura
Background: The structure and risk factors for cardiovascular diseases (CVD) in Japan may change because lifestyle, particularly nutrition, socioeconomic status, and medical care, which affect CVD, may markedly change over time. Therefore, a new prospective cohort study on a representative general Japanese population based on national surveys is required.Methods: In November 2010, the baseline survey of the National Integrated Project for Prospective Observation of Non-communicable Disease and its Trends in the Aged 2010 (NIPPON DATA2010) was performed with the National Health and Nutrition Survey of Japan (NHNS2010) in 300 randomly selected districts throughout Japan. The survey included a questionnaire, electrocardiogram, urinalysis, and blood biomarkers added to the NHNS2010 examinations. Physical measurements, blood biomarkers, and dietary data were also obtained in NHNS2010. Socioeconomic factors were obtained by merging with the Comprehensive Survey of Living Conditions 2010 (CSLC2010) dataset. Participants are followed annually for the incidence of diabetes mellitus, CVD events (acute coronary events, heart failure, atrial fibrillation, and stroke), and cause-specific mortality. The activities of daily living are followed every 5 years.Results: A total of 2,898 individuals aged 20 years or older agreed to participate in the baseline survey of NIPPON DATA2010. The participation rate was 74.6%. Of these, data from NHNS2010 was merged for 2,891 participants (1,236 men and 1,655 women). The data of 2,807 participants were also merged with CSLC2010 data.Conclusions: We established NIPPON DATA2010 as a cohort study on a representative general Japanese population that covers all of Japan.

5 February 2020 in Journal of Epidemiology
Verified
Journal Article
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YYYunqing Yang
Yunqing Yang
AHAtsushi Hozawa
Atsushi Hozawa
MKMana Kogure
Mana Kogure
ANAkira Narita
Akira Narita
THTakumi Hirata
Takumi Hirata
KMKatsuyuki Miura
Katsuyuki Miura
Background: It has been reported that chronic inflammation may play an important role in the pathogenesis of several serious diseases and could be modulated by diet. Recently, the Dietary Inflammatory Index (DII®) was developed to assess the inflammatory potential of the overall diet. The DII has been reported as relevant to various diseases but has not been validated in Japanese. Thus in the present study, we analyzed the relationship between DII scores and high-sensitivity C-reactive protein (hs-CRP) levels in a Japanese population.Methods: Data of the National Integrated Project for Prospective Observation of Non-communicable Disease and its Trends in the Aged 2010 (NIPPON DATA2010), which contained 2898 participants who aged 20 years or older from the National Health and Nutrition Survey of Japan (NHNS2010), were analyzed. Nutrient intakes derived from one-day semi-weighing dietary records were used to calculate DII scores. Energy was adjusted by residual method. Levels of hs-CRP were evaluated using nephelometric immunoassay. Multiple linear regression analyses were performed.Result: After adjusting for age, sex, smoking status, BMI and physical activity, a significant association was observed between DII scores and log(CRP+1) (standard regression coefficient=0.05, p<0.01). And although it was not statistically significant, the positive association was consistently observed in almost all age-sex subgroups and the non-smoker subgroup.Conclusions: The current study confirmed that DII score was positively associated with hs-CRP in Japanese.

17 March 2020 in Nutrients
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Journal Article
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NONagako Okuda
Nagako Okuda
AOAkira Okayama
Akira Okayama
KMKatsuyuki Miura
Katsuyuki Miura
KYKatsushi Yoshita
Katsushi Yoshita
NMNaoko Miyagawa
Naoko Miyagawa
JSJeremiah Stamler
Jeremiah Stamler
A lower-than-recommended potassium intake is a well-established risk factor for increased blood pressure. Although the Japanese diet is associated with higher sodium intake and lower potassium intake, few studies have examined the source foods quantitatively. Studies on dietary patterns in association with potassium intake will be useful to provide dietary advice to increase potassium intake. Twenty-four-hour (hr) dietary recall data and 24-hr urinary potassium excretion data from Japanese participants (574 men and 571 women) in the International Study of Macro/Micronutrients and Blood Pressure (INTERMAP) were used to calculate food sources of potassium and compare food consumption patterns among quartiles of participants categorized according to 24-hr urinary potassium excretion per unit of body weight (UK/BW). The average potassium intake was 2791 mg/day per participant, and the major sources were vegetables and fruits (1262 mg/day), fish (333 mg/day), coffee and tea (206 mg/day), and milk and dairy products (200 mg/day). Participants in the higher UK/BW quartile consumed significantly more vegetables and fruits, fish, and milk and dairy products, and ate less rice and noodles. Conclusion: Advice to increase the intake of vegetables and fruits, fish, and milk may be useful to increase potassium intake in Japan.

16 February 2012 in Neuroepidemiology
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Journal Article
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Tanvir C TurinTanvir C Turin
Tanvir C Turin
YKYoshikuni Kita
Yoshikuni Kita
NRNahid Rumana
Nahid Rumana
YNYasuyuki Nakamura
Yasuyuki Nakamura
KUKayo Ueda
Kayo Ueda
HUHirotsugu Ueshima
Hirotsugu Ueshima
Background: Exposure to high levels of air pollution can increase the risk of cardiovascular events. However, there is no clear information in Japan on the effect of pollution on the incidence of stroke and acute myocardial infarction (AMI). Therefore, we investigated the effects of air pollution on the incidence of stroke and AMI in a setting where pollutant levels are rather low. Methods: Data were obtained from the Takashima Stroke and AMI Registry, which covers a population of approximately 55,000 in Takashima County in central Japan. We applied a time-stratified, bidirectional, case-crossover design to estimate the effects of air pollutants, which included suspended particulate matter (SPM), sulfur dioxide (SO2), nitrogen dioxide (NO2) and photochemical oxidants (Ox). We used the distributed lag model to estimate the effect of pollutant exposure 0-3 days before the day of event onset and controlled for meteorological covariates in all of the models. Results: There were 2,038 first-ever strokes (1,083 men, 955 women) and 429 first-ever AMI cases (281 men, 148 women) during 1988-2004. The mean pollutant levels were as follows: SPM 26.9 µg/m3; SO2 3.9 ppb; NO2 16.0 ppb, and Ox 28.4 ppb. In single-pollutant and two-pollutant models, SO2 was associated with the risk of cerebral hemorrhage. Other stroke subtypes and AMI were not associated with air pollutant levels. Conclusions: We observed an association between SO2 and hemorrhagic stroke; however, we found inconclusive evidence for a short-term effect of air pollution on the incidence of other stroke types and AMI.