Understanding the decline of mean systolic blood pressure in Japan: an analysis of pooled data from the National Nutrition Survey, 1986–2002
Nayu Ikeda, Emmanuela Gakidou, Toshihiko Hasegawa & Christopher JL Murray
Volume 86, Number 12, December 2008, 978-988
Table 1. Description of variables used in the regression analysis, based on data from the National Nutrition Survey, Japan, 1986–2000
| Variable | Survey year | Possible values | Reference categories/ analytic strategies |
|---|---|---|---|
| Measured SBPa | 1986–2002 | Continuous in mmHg | |
| Age (years) | 1986–2002 | 20–29, 30–34, 35–39, 40–44, 45–49, 50–54, 55–59, 60–64, 65–69, 70–74, 75+ | 20–29 |
| Measured BMIb | 1986–2002 | Continuous in kg/m² | Interacted with age |
| Regular exercisec | 1986–1989 | “Yes”/“No” | “No” |
| 1990–2002 | “Unable to do for health reasons,” “Unable to do for other reasons,” “Currently doing regular exercise” | “Unable to do for health reasons” or “Unable to do for other reasons” | |
| Current smokerc | 1986–2002 | “Never,” “Discontinued,” “Currently smoking” | “Never” or “Discontinued” |
| Current drinkerc | 1986–1989 | “Yes”/“No” | “No” |
| 1990–2002 | “Never or rarely,” “Discontinued,” “Currently drinking” | “Never or rarely” or “Discontinued” | |
| Daily salt intake per capita by prefecture (g)d | 1986–2002 | Salt intake in grams | |
| Antihypertensive medication use | 1986–1989 | “Taking,” “Not taking” | “Not taking” |
| 1990–2002 | “Never,” “Discontinued,” “Taking occasionally,” “Taking daily” | “Never,” “Discontinued” or “Taking occasionally” | |
| Survey year | 1986–2002 | 1986–2002 | 1986 |
BMI, body mass index; SBP, systolic blood pressure.
a Using a Riva-Rocci mercury manometer and no specification on cuff size, certified professionals such as medical doctors, public health nurses and registered nurses measured blood pressure in the right upper arm of seated persons after 5 minutes’ rest. Systolic and diastolic blood pressures were recorded once until 1999 and twice starting in 2000. The first measurement of SBP was used for consistency of measurements in this analysis.
b Using a spring scale and a stadiometer, public health nurses measured the height and weight of participants wearing light clothes and no shoes.
c In the survey, individuals were considered to have regular exercise if they had exercised for more than 30 minutes at a time more than twice a week for over 1 year; they were considered current smokers if they smoked daily or occasionally; and they were considered current drinkers if they consumed more than one standard cup of Japanese sake, one large bottle of regular beer, or one double measure of whisky at a time more than three times a week.
d Japan has 47 prefectures (local governing units). Daily salt intake per capita at the prefecture level in each survey year was used as a reference for individual salt intake because it afforded the best available data between 1986 and 1994. Nutrition intake was recorded at the household level only, and microdata on nutrition intake were not available during this period. Data were obtained for the 1986–1994 surveys from the Health and Nutrition Information Infrastructure Database based on the NNS, available from: http://nihn-jst.nih.go.jp:8888/nns/owa/nns_main_e.hm01a [accessed on 7 February 2007]. For the 1995–2002 surveys we aggregated microdata to obtain the variable.