Are popular books about diet and health written based on scientific evidence? A comparison of citations between the USA and Japan.

OBJECTIVES: To describe and compare the references cited in popular books about diet and health between the USA and Japan. DESIGN: Books were selected based on their best-seller rankings in the diet and health category of online bookstores. We identified references throughout all pages of the books and examined the number of references, reference format (identifiable or not) and presence of specific types of references, such as systematic reviews of human research. We compared the characteristics of references between the two countries and examined related factors to citation. SETTING: Cross-sectional study. PARTICIPANTS: Books (n 100 in each country). RESULTS: Among 100 books from each country, sixty-five US and sixty-six Japanese books had references. Forty-five US books cited more than 100 references, against only five Japanese books. The number of books that cited systematic reviews of human research differed between the USA (n 49) and Japan (n 9). Additionally, the number of books that provided identifiable information for all references was significantly higher in the USA (n 63) than in Japan (n 42). Books whose first authors have licences of medical doctors were more likely to cite references than those without in both countries. CONCLUSIONS: Two-thirds of books about diet and health cited references in both the USA and Japan, but Japanese books cited fewer references and were less likely to cite systematic reviews and provide identifiable references than US books. Further research into the scientific reliability of information in books about diet and health is warranted.

Association between dietary pattern and insomnia symptoms among independent older adults: A cross-sectional study based on JAGES.

BACKGROUND: Poor diet can cause sleep disorders; however, this association has not been established in older populations. This study investigated the association between dietary patterns and insomnia symptoms in independent older adults. METHODS: This cross-sectional study targeted independent older Japanese adults aged ≥74 years. We used insomnia symptoms classified into three domains: difficulty initiating sleep (DIS), difficulty maintaining sleep (DMS), and insomnia. These symptoms were assessed as dependent variables by a self-reported questionnaire. Dietary patterns (DP), identified by principal component analysis of a self-administered diet history questionnaire, were used as independent variables. Poisson regression analysis was used to estimate the prevalence ratios and 95% confidence intervals with adjustment for potential confounders. RESULTS: Among 1,311 participants (mean age = 80.1; women, 48.5%), we identified three dietary patterns: DP1 was characterized by a high intake of vegetables, soy products, and fruits and a low intake of rice; DP2 was characterized by a high intake of fish, chicken, processed meat, and noodles and a low intake of soy products; and DP3 was characterized by a lower intake of fruits and confectionaries. Higher DP1 scores were significantly associated with a lower prevalence of DIS (p-for-trend = 0.012). A higher DP2 score was significantly associated with a higher prevalence of insomnia (p-for-trend = 0.032). There was no significant association between DP3 and insomnia symptoms (p-for-trend >0.05). CONCLUSION: Our results highlighted that a dietary pattern with a high intake of vegetables, soy products, and fruits may contribute to reducing insomnia symptoms among independent older adults.

Cooking skills modify the association between oral health and mortality.

Poor oral health has been linked to an increased risk of mortality. People with good cooking skills may be able to cope with problems caused by oral dysfunction, such as restricted food choice. This study investigated whether cooking skills modified the association between oral health status and mortality. A 3-year follow-up was conducted among participants of the Japan Gerontological Evaluation Study, a population-based cohort study of Japanese adults aged 65-101 years. Oral health assessment comprised number of teeth and three oral functions (awareness of swallowing difficulty, decline in masticatory function, and dry mouth). Cooking skills were assessed using a valid scale adapted for Japanese participants. Mortality from 2016 to 2019 was analysed for 10,121 respondents. Cox regression models were used to estimate hazard ratios for mortality risk adjusting for potential confounders, including sociodemographic factors and health status. During the follow-up, there were 488 deaths (4.8% of all participants). Both fewer teeth and poor oral function were associated with a greater mortality risk. Cooking skills modified the association only for oral function. Stratification by cooking skill score showed that the hazard ratios for ≥2 oral difficulties (vs. none) was 2.06 (95% confidence interval: 1.43-2.96) among those with low cooking skills and 1.25 (95% confidence interval: 0.92-1.71) among those with high cooking skills after adjusting for potential confounders. Improving cooking skills may be key to mitigating health risks owing to poor oral functions.

Changes in Body Mass Index on the Risk of Back Pain: Estimating the Impacts of Weight Gain and Loss.

BACKGROUND: The relationship between obesity and back pain in older populations is poorly understood. This study aimed to examine (a) the impacts of changes in obesity status on back pain risk and (b) the heterogeneity in the influence of changes in obesity status according to muscle strength. METHODS: We analyzed 6 868 participants in waves 4 (2008-2009), 6 (2012-2013), and 7 (2014-2015) of the English Longitudinal Study of Ageing. The exposure comprised continuous body mass index (BMI) values, whereas the outcome comprised self-reported moderate or severe back pain. The targeted minimum loss-based estimator was used to estimate the impacts of hypothetical changes in BMI in each wave under 10 scenarios encompassing a 5%-25% hypothetical reduction/increase in BMI. We also performed stratified analysis using handgrip strength at the baseline. RESULTS: For the hypothetical reduction scenarios, a 10% (relative risk [RR]; 95% confidence interval [CI] = 0.82 [0.73-0.92], p = .001) reduction in BMI estimated a significantly lower back pain risk compared to the observed data. For the hypothetical increase scenarios, a 5% (RR [95% CI] = 1.11 [1.04-1.19], p = .002) increase in BMI estimated a significantly higher back pain risk. Increased BMI had a higher risk of back pain among those with weak strength when stratified by handgrip strength but not among those with strong strength. CONCLUSION: Our study confirmed that weight gain leads to a greater risk of back pain as well as heterogeneity in the influence of changes in obesity status according to the handgrip strength.

Information Usage and Compliance with Preventive Behaviors for COVID-19: A Longitudinal Study with Data from the JACSIS 2020/JASTIS 2021.

The influence of different types of information sources on individual preventive behaviors remains unclear. We aimed to investigate the associations between individual information usage to obtain information about COVID-19 and compliance with preventive behaviors. This longitudinal study was based on an Internet survey conducted in August−September 2020 and February 2021. We used compliance with four preventive behaviors for COVID-19, "wearing a mask", "ventilation", "social distancing", and "avoiding crowds" as outcome variables, and 20 types of information sources based on people or institutions (Medical worker, Government, etc.) and media (TV news, Twitter, etc.) as predictors. Absolute differences and 95% confidence intervals were estimated using generalized estimating equations adjusted for possible confounders. Among the 18,151 participants aged 20−79, the mean age was 51.7 (SD = 15.9) in 2020, and 51.3% were male. In total, compliance with "wearing a mask", "ventilation", "social distancing", and "avoiding crowds" was seen in 86.2%, 46.9%, 45.4%, and 62.6% of individuals in 2020, and 89.3%, 38.2%, 47.2%, and 61.6% of individuals in 2021, respectively. In the multivariate analysis, "medical workers", "professionals", "the government", "Twitter", "news websites", and "TV news" were positively associated with compliance with two or more preventive behaviors (p < 0.05). The type of information source may play an important role in providing information for COVID-19 prevention.

Association of poor dental status with eating alone: A cross-sectional Japan gerontological evaluation study among independent older adults.

Eating alone is reported to deteriorate health; however, the relationship between eating alone and poor dental health remains unclear. This cross-sectional study aimed to investigate the association between poor dental health and eating alone. Data of participants (n = 156,287) aged ≥65 years from the Japan Gerontological Evaluation Study were evaluated using logistic regression to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for the association between dental status, including prosthesis use, and eating status. Differences in these associations according to living status were also examined. The mean age of participants was 73.7 (SD = 6.0) years. The percentages of participants eating alone with 20 or more teeth, 10-19 teeth with dental prostheses, 0-9 teeth with dental prostheses, 10-19 teeth without dental prostheses, and 0-9 teeth without dental prostheses were 13.8%, 16.0%, 18.6%, 18.9%, and 27.0%, respectively. After adjusting for covariates, participants with 0-9 teeth without any dental prosthesis showed a significantly higher odds ratio for eating alone (OR = 1.81, 95% CI = 1.58-2.07) than those with 20 or more teeth. Among participants with poorer dental status, the probability of eating alone was higher in those living alone than in those living with others. Among older adults, poor dental status was significantly associated with eating alone, and this association was stronger among those living alone. Maintaining better dental status by using a dental prosthesis might reduce the risk of eating alone, especially for those living alone.