Hiroyuki Doi’s research while affiliated with Okayama University and other places

Background Body mass index (BMI) is a significant predictor of functional disability in older adults. However, when evaluated, the association between BMI and incident functional disability, considering behaviors only as covariates or not, may not be appropriate. The primary purpose of the study was to investigate the combined effects of BMI and unhealthy behaviors on the risk of incident functional disability. Methods This was a retrospective cohort study that took place in Okayama City, Japan. Data on BMI and unhealthy behaviors were obtained using the health check-up questionnaire. The certification of Long-Term Care Insurance was used to measure functional disability. Cox proportional hazard models were used; adjusted hazard ratios (HRs) with 95% confidence interval (CI) were calculated for incidence of functional disability across categories of BMI and number of unhealthy behaviors. Results The relationship between BMI and incident functional disability was U-shaped (HR = 1.18, 95% CI [1.11–1.25], among the underweight range; and 1.26 [1.19–1.34] among the obesity range), and its risk was significantly higher within the normal-to-overweight range of BMI values with co-occurring unhealthy behaviors (with normal weight range and one, 1.17 [1.01–1.21]; two, 1.29 [1.18–1.41]; and three or four unhealthy behaviors 1.38 [1.24–1.54]; as well as among overweight range and one, 1.16 [1.05–1.27]; two, 1.26 [1.15–1.38]; and three or four unhealthy behaviors, 1.47 [1.31–1.64]). In each BMI category, the risk of incident functional disability increased with increasing number of unhealthy behaviors ( p < 0.05 for linear tread), with the highest risk (1.87 [1.58–2.20]) occurring in combination with at least three unhealthy behaviors with BMI ≥ 27.5, for both sexes (2.20 [1.64–2.92] in men and 1.66 [1.35–2.04] in women). Conclusion It is necessary to consider the combined effects of BMI and behaviors on incident functional disability. Furthermore, interventions targeting multiple behaviors should be considered as such interventions may offer greater benefits than simple interventions.

Neuromuscular blocking agents play a significant role in improving the success rate for urgent intubation, although there is limited evidence about the effect on subsequent outcomes, such as the incidence of tracheostomy. In this retrospective cohort study, we aimed to examine the association between avoidance of neuromuscular blocking agents for urgent tracheal intubation and incidence of tracheostomy among patients in the intensive care unit (ICU). The setting of this study was an eight-bed ICU at a tertiary-care hospital in Okayama, Japan. We included patients who underwent urgent tracheal intubation at the emergency department or the ICU and were admitted to the ICU between April 2013 and November 2017. We extracted data on methods and medications of intubation, predictors for difficult intubation, Cormack–Lehane grade, patient demographics, primary diagnoses, reintubation. We estimated odds ratios and their 95% confidence intervals for elective tracheostomy during the ICU stay using logistic regression models. Of 411 patients, 46 patients underwent intubation without neuromuscular blocking agents and 61 patients underwent tracheostomy. After adjusting for potential confounders, patients who avoided neuromuscular blocking agents had more than double the odds of tracheostomy (odds ratio 2.59, 95% confidence interval 1.06–6.34, p value = 0.04). When stratifying the subjects by risk status for tracheostomy, the association was more pronounced in high-risk group, while we observed less significant association in the low-risk group. Avoidance of neuromuscular blocking agents for urgent intubation increases the risk of tracheostomy among emergency patients, especially those who have a higher risk for tracheostomy.

Background: Although breastfeeding has been well-established as the preferred method for infant nutrition, its prophylactic effects on food allergy remain controversial. Infantile eczema has been linked to food allergy via percutaneous sensitization; however, this relationship has not been considered in previous studies. We aimed to uncover the prophylactic effects of breastfeeding on food allergy, focusing on eczema-mediated percutaneous sensitization. Methods: This retrospective cohort study was based on 46,616 children from the Longitudinal Survey of Newborns in the 21st Century in Japan, begun in 2001. We classified participants into three groups based on infant feeding practices (exclusive breastfeeding, partial breastfeeding including only colostrum, and formula feeding only) and used information from at least one outpatient visit for food allergy during two observation periods (age 6-18 months and age 6-66 months) as health outcomes. We performed log-binomial regression analysis adjusted for potential confounders and stratified analysis according to infantile eczema status. Results: Compared with formula feeding, partial breastfeeding including only colostrum reduced the risk of food allergy only in children with infantile eczema, (RR = 0.66, 95% CI: 0.46, 0.96 for age 6-66 months), whereas exclusive breastfeeding increased this risk in those without infantile eczema (RR = 2.41, 95% CI: 1.40, 4.15, age 6-66 months). The prophylactic effects of breastfeeding on food allergy in the infantile eczema group increased with shorter breastfeeding duration. Conclusions: Our results showed that breastfeeding, especially colostrum, had prophylactic effects on food allergy only among high-risk children with infantile eczema whereas prolonged breastfeeding increased the risk of food allergy.

Aim: To evaluate the association between the amount and frequency of alcohol consumption and incident dementia in older Japanese adults using large sample size data over a long follow-up period. Methods: This was a retrospective cohort study carried out in Japan. A total of 53 311 older adults were followed from 2008 to 2014. A health checkup questionnaire was used to assess the amount and frequency of alcohol consumption. The Dementia Scale of long-term care insurance was used as a measure of incident dementia. Cox proportional hazards models were used to calculate adjusted hazard ratios, with their 95% confidence intervals, for the incidence of dementia across the categories of alcohol consumption by sex. Results: During a 7-year follow-up period, 14 479 participants were regarded as having incident dementia. Compared with non-drinkers, the multivariate adjusted hazard ratios for participants with alcohol consumption ≤2 units per day, occasionally (0.88, 95% CI 0.81-0.96 in men and 0.84, 95% 0.79-0.90 in women) and daily (0.79, 95% 0.73-0.85 in men and 0.87, 95% 0.78-0.97 in women) were statistically significant, and the difference between occasional and daily consumption was only statistically significant in men; however, for participants with alcohol consumption >2 units per day, occasionally (0.91, 95% 0.71-1.16 in men and 1.09, 95% 0.72-1.67 in women) and daily (0.89, 95% 0.81-1.00 in men and 1.16, 95% 0.84-1.81 in women) were not significant. Conclusions: Alcohol consumption of ≤2 units per day, occasionally or daily, could reduce the risk of incident dementia, with greater benefit for men with such daily consumption. Geriatr Gerontol Int 2019; ••: ••-••.

Objective To evaluate the association between regular physical activity and the risk of incident dementia in older Japanese adults. Methods This was a retrospective cohort study performed in Okayama City, Japan. Overall, 51,477 older Japanese adults were followed from 2008 to 2014. A health checkup questionnaire was used to assess regular physical activity. The Dementia Scale of long‐term care insurance was used as a measure of incident dementia. Cox proportional hazard models were used to calculate adjusted hazard ratios, with their 95% confidence intervals, for the incidence of dementia across the categories of physical activity. Results During a 7‐year of follow‐up, 13,816 subjects were considered as having incident dementia. Compared to participants who performed physical activity ≤ 1 time/week, the multivariate adjusted hazard ratio values (95% confidence intervals) for participants who performed physical activity ≥ 2 times/week but not every day and those who performed physical activity every day were 0.79 (0.75–0.84) and 0.94 (0.89–0.98), respectively. The interaction of physical activity and sex was statistically significant (p < 0.01). In subgroup analysis, the multivariate adjusted hazard ratio values (95% confidence intervals) remained low, at 0.76 (0.70–0.84) in males and 0.81 (0.76–0.87) in females who performed physical activity ≥ 2 times/week but not every day; they were 0.82 (0.76–0.89) in males and 1.01 (0.95–1.07) in females who performed physical activity every day. Conclusions Regular physical activity could reduce the risk of incident dementia in older Japanese adults, except females who performed physical activity every day.

Objective To examine the relationship between the catch-up growth of preterm, SGA children and their behavioral development. Methods We analyzed data from a large Japanese, nationwide, population-based, longitudinal survey that started in 2001. We restricted the study participants to preterm children with information on height at 2 years of age (n = 1667). Catch-up growth for SGA infants was defined as achieving a height at 2 years of age above −2.0 standard deviations for chronological age. We then used logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs) for the associations of SGA/catch-up status with neurobehavioral development both at 5.5 and 8 years of age, adjusting for potential infant- and parent-related confounding factors. Results Twenty-six percent of preterm SGA infants failed to catch up. SGA children without catch-up growth were more likely to be unable to listen without fidgeting (OR 2.51, 95% CI: 1.06–5.93) and unable to focus on one task (OR 2.66, 95% CI: 1.09–6.48) compared with non-SGA children at 5.5 years of age. Furthermore, SGA children without catch-up growth were at significant risk for inattention at 8 years of age. Conclusions SGA infants with poor postnatal growth were at risk for attention problems throughout preschool-age to school-age among preterm infants. Early detection and intervention for attention problems among these infants is warranted.

Background: A number of studies have linked long-term exposure to particulate matter with aerodynamic diameter <2.5 µm (PM2.5) with mortality, but most of these studies were conducted in Europe and North America. Studies in Asian countries had been conducted at relatively high exposures. We evaluated the association of long-term exposure to PM2.5 and natural-cause and cause-specific mortality in Japan, where PM2.5 levels are relatively low compared with levels in other Asian countries. Methods: A cohort of 75,531 participants underwent basic health checkups in Okayama City in 2006 or 2007. We followed the participants until the end of 2016. Average PM2.5 levels from 2006 to 2010 were obtained and assigned to the participants by geographical location. We used the Cox proportional hazard models to estimate hazard ratios for a 5-μg/m3 increase in PM2.5 levels for natural-cause or cause-specific mortality, adjusting for potential confounders. Results: PM2.5 exposure was associated with increased risk of mortality; the hazard ratios were 1.29 (95% confidence interval = 1.18, 1.41) for mortality from natural causes, 1.16 (1.02, 1.32) for cardiorespiratory mortality, and 1.63 (1.13, 2.34) for lung cancer mortality. PM2.5 exposure was more strongly associated with cardiorespiratory mortality from hypertension, pneumonia and influenza, and chronic obstructive pulmonary disease than with ischemic heart disease or cerebrovascular disease. Elderly participants and smokers tended to have higher effect estimates. Conclusion: Long-term exposure to PM2.5 can increase the risk of natural-cause, cardiorespiratory, and lung cancer mortality in Japan.

Background The prevalence of multiple births has recently increased. However, the association between gestational age and long-term morbidity among twins remains unclear. Aims To examine the association of gestational age with child health and neurological development in early childhood among twins. Study design Population-based longitudinal study. Subjects We included 947 children from 479 pairs of twins with information on gestational age. Outcome measures Hospitalization was used as an indicator of physical health, and responses to questions about age-appropriate behaviors were used as an indicator of neurobehavioral development. We conducted binomial log-linear regression analyses, controlling for both child and maternal variables in the model. We accounted for correlations within the pairs with generalized estimating equations. Results The early term group (i.e., 37 to 38 weeks of gestation) had a lower risk of poor child health and unfavorable neurodevelopment compared with the full term group (≥39 weeks of gestation) and preterm group (<37 weeks of gestation). Compared with the early term group, the adjusted risk ratios for hospitalization for all causes during the period from 7 to 18 months of age was 2.2 (95% confidence interval: 1.3–3.8) for very preterm children (<32 weeks of gestation), 1.1 (0.8–1.6) for moderately and late preterm children (32 to 36 weeks of gestation), and 1.8 (1.0–3.2) for full term children. Conclusion We observed a U-shaped association of gestational age with child health and neurodevelopment. The early term group had the lowest risk of poor outcomes among twins.

The association between early daycare attendance and risk of allergic diseases remains inconclusive. Therefore, we examined the association among Japanese children on a long-term basis using a nationwide longitudinal survey data. We estimated the association between daycare attendance at age 6 or 18 months and allergy development using information on outpatient visits for atopic dermatitis (AD), food allergy (FA), and asthma and admission for asthma up to 12 years of age as a proxy for developing these diseases, with multilevel logistic regression. Early daycare attendance was associated with increased odds of AD at ages 2.5–3.5 years: the adjusted odds ratio (OR) was 1.34 [95% CI: 1.21, 1.47]. The association with FA was equivocal. The odds of asthma was increased before age 3.5 years and afterwards decreased: the adjusted ORs were 1.60 [1.44, 1.77] for ages 1.5–2.5 years and 0.77 [0.69, 0.87] for ages 5.5–7 years. The effect of early daycare attendance depends on the type of allergies.

Kawasaki disease is the leading cause of acquired childhood heart disease in most developed countries, but the etiology of the disease is unknown. An aberrant immune response to some environmental triggers may play a role and involuntary exposure to tobacco smoke can alter immune functions. We thus prospectively examined the association between early childhood exposure to maternal smoking and the incidence of Kawasaki disease. We used a large, nationwide population-based longitudinal survey ongoing since 2010 and restricted participants to a total of 38,444 children for whom information on maternal smoking was available. Maternal smoking status was ascertained at 6 months of age, and responses to questions about hospital admission for Kawasaki disease between the ages of 6 and 30 months were used as outcome. We conducted binomial log-linear regression analyses adjusting for children's, parental, and residential factors with children of non-smoking mothers as our reference group. Maternal smoking increased the risk of admission, in particular for the period between 6 and 18 months of age, in a dose-dependent manner. Compared with children of non-smoking mothers, the children of mothers who smoked had a risk ratio of 1.83 (95% confidence interval: 1.06, 3.35) for hospital admissions between 6 and 30 months of age and a risk ratio of 2.69 (95% confidence interval: 1.56, 4.64) for hospital admissions between 6 and 18 months of age. Early childhood exposure to maternal smoking may increase the risk of Kawasaki disease hospitalizations in childhood.