Objective Ferritin is involved in the occurrence of oxidative stress and regulation of adiponectin, both of which can modulate metabolic syndrome (MetS). To investigate the association of ferritin with MetS in Japanese, a cross-sectional study was conducted involving 324 men and 340 women who underwent anti-aging health checks at Tokai University Tokyo Hospital.
 Methods The MetS criteria of the Japanese Society of Internal Medicine was used and the levels of serum ferritin and high sensitivity C-reactive protein (hsCRP) were compared with or without MetS-related abnormalities (abdominal obesity, waist circumference ≥ 85 cm in men and ≥ 90 cm in women; hypertension, systolic BP ≥ 130 and/or diastolic BP ≥ 85 mmHg; hyperglycemia, fasting glucose ≥ 110 mg/dL; and dyslipidemia, triglycerides ≥ 150 mg/dL and/or HDL-C < 40 mg/dL).
 Results Ferritin levels were significantly higher in the subjects with hyperglycemia and dyslipidemia in both men and women, and in those with abdominal obesity in women. HsCRP levels were significantly higher in the subjects with abdominal obesity in both sexes, and in those with hypertension in men. Serum ferritin increased in proportion to the number of MetS components and was significantly higher in MetS subjects than in non-MetS counterparts in both men and women, although these results were not obtained regarding hsCRP.
 Conclusion Ferritin is not considered inferior compared with the well-known marker hsCRP with respect to the association with MetS. High serum ferritin concentrations could potentially be used as a biomarker for MetS as well as hsCRP.

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 Objective. The purpose of the study was to determine the distribution of estimated glomerular filtration rate (eGFR) values among the Japanese working generation using representative health checkup data.
 Design. Cross-sectional, observational, large cohort study
 Setting. Japan Health Insurance Association, Tokyo Branch
 Participants. Data for 766,556 participants aged 35-74 years who attended preventative health checkup for lifestyle-related disease conducted by the Japan Health Insurance Association, Tokyo Branch, in 2012 were included. After excluding dialysis patients and those with missing data, 766,095 participants (mean age, 48.9 years; 68.1% male) were selected for analysis.
 Main outcome measures. Serum creatinine-based eGFR values were analyzed in 5-year age groups.
 Results. The age-specific mean eGFR values were 86.4, 83.0, 79.8, 77.4, 75.5, 73.2, 70.9, and 67.8 mL/min/1.73 m² for the age groups of 35-39, 40-44, 45-49, 50-54, 55-59, 60-64, 65-69, and 70-74 years, respectively. The difference in eGFR per 1-year difference in age was 0.523 mL/min/1.73 m²/year. The mean eGFR was higher in the female participants for all age groups, being most apparent in those aged 35-50 and 60-74 years. However, without body surface-area correction, the mean eGFR was lower in the female participants for all age groups.
 Conclusion We described the distribution of eGFR values on the basis of a large data set obtained during health checkup examinations in Japan. We found these data to be representative of the 35-74 year-old Japanese general population.

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 Health examinations requiring short hospital stays began in the 1950s in Japan, and automated health checks using automated screening devices and computers began in the 1960s in the United States. Automated health checks have now become standard for general health examinations in Japan. While voluntary health examinations went into decline in Western countries mostly due to a lack of evidence on improving health by health examinations, more than 5 million subjects are receiving health examinations each year in Japan. Moreover, a type of medical tourism promoted increase in number of people visiting Japan to undergo health examinations. Although views concerning personal health, preventative medicine and medical evidence are different in Western countries versus Japan, we need to disseminate information from Japan regarding the concept of our excellent health examination system globally.

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