Section of Population Health Metrics, International Center for Nutrition and Information, National Institute of Health and Nutrition, National Institutes of Biomedical Innovation, Health and Nutrition, Tokyo, Japan.
Graduate School of Environmental Studies, Tohoku University, Sendai, Japan.
Front Public Health. 2022 May 20;10:830578. doi: 10.3389/fpubh.2022.830578. eCollection 2022.
Among high-income countries, Japan has a low prevalence of obesity, but little is understood about subnational trends and variations in body mass index (BMI), largely owing to the lack of data from representative samples of prefectures. We aimed to examine long-term trends and distributions of adult BMI at the prefecture level in Japan from the late 1970s using a spatiotemporal model.
We obtained cross-sectional data for 233,988 men and 261,086 women aged 20-79 years from the 44 annual National Health and Nutrition Surveys (NHNS) conducted during 1975-2018. We applied a Bayesian spatiotemporal model to estimate the annual time series of age-standardized and age-specific mean BMI by 20-year age group and sex for each of the 47 prefectures. We assessed socioeconomic inequalities in BMI across prefectures using the concentration index, according to population density.
In men, the age-standardized prefectural mean BMI ranged from 21.7 kg/m (95% credible interval, 21.6-21.9) to 23.1 kg/m (22.9-23.4) in 1975 and from 23.5 kg/m (23.3-23.7) to 24.8 kg/m (24.6-25.1) in 2018. In women, the age-standardized prefectural mean BMI ranged from 22.0 kg/m (21.9-22.2) to 23.4 kg/m (23.2-23.6) in 1975 and from 21.7 kg/m (21.6-22.0) to 23.5 kg/m (23.2-23.8) in 2018. Mean BMI was highest in the southernmost prefecture for most of the study period, followed by northeast prefectures. The increase in mean BMI was largest in southwest prefectures, which caught up with northeast prefectures over time. The concentration index was negative, indicating higher BMI in less-populated prefectures. Absolute values of the concentration index were greater in women than in men and increased over time.
There were variations in adult mean BMI across prefectures, and geographic distributions changed over time. Further national and local efforts are needed to address the rising trend in mean BMI, particularly among men in rural prefectures, and socioeconomic inequalities among women. Bayesian hierarchical modeling is useful for reconstructing long-term spatiotemporal trends of mean BMI by integrating small-sized survey samples at the prefecture level in the NHNS.
在高收入国家中，日本的肥胖患病率较低，但对于各都道府县的体重指数（BMI）的亚国家趋势和变化知之甚少，主要是因为缺乏来自代表性都道府县样本的数据。我们旨在使用时空模型检查日本从 20 世纪 70 年代末开始的成年 BMI 的长期趋势和分布。
我们从 1975 年至 2018 年进行的 44 次年度国家健康和营养调查（NHNS）中获得了 233988 名男性和 261086 名 20-79 岁女性的横断面数据。我们应用贝叶斯时空模型来估计每个都道府县 47 个 20 岁年龄组和性别的年龄标准化和年龄特异性平均 BMI 的年度时间序列。我们根据人口密度，使用集中指数评估了 BMI 在都道府县之间的社会经济不平等情况。
在男性中，1975 年时，年龄标准化的都道府县平均 BMI 范围为 21.7kg/m（95%可信区间为 21.6-21.9）至 23.1kg/m（22.9-23.4），2018 年时，年龄标准化的都道府县平均 BMI 范围为 23.5kg/m（23.3-23.7）至 24.8kg/m（24.6-25.1）。在女性中，1975 年时，年龄标准化的都道府县平均 BMI 范围为 22.0kg/m（21.9-22.2）至 23.4kg/m（23.2-23.6），2018 年时，年龄标准化的都道府县平均 BMI 范围为 21.7kg/m（21.6-22.0）至 23.5kg/m（23.2-23.8）。在研究期间的大部分时间里，最南端的都道府县的平均 BMI 最高，其次是东北部的都道府县。平均 BMI 的增长最大的是西南部的都道府县，随着时间的推移，它们赶上了东北部的都道府县。集中指数为负值，表明人口较少的都道府县的 BMI 更高。集中指数的绝对值在女性中大于男性，并且随着时间的推移而增加。
都道府县的成年平均 BMI 存在差异，并且地理分布随时间发生变化。需要进一步在全国和地方层面采取措施，以解决平均 BMI 的上升趋势，特别是农村地区男性的上升趋势，以及女性之间的社会经济不平等问题。贝叶斯层次模型对于通过整合 NHNS 中都道府县层面的小型调查样本来重建平均 BMI 的长期时空趋势非常有用。
