Nobuhiro Tone

Stronger association of indoor temperature than outdoor temperature with blood pressure in colder months.

Background: Higher cardiovascular mortality in winter may be partly explained by increased blood pressure (BP) because of cold exposure. However, this winter excess mortality is higher in countries with moderate winter than those with severe winter climate. Objectives: Although higher BP in low outdoor temperatures has been reported, the magnitude of association of indoor temperature with ambulatory BP remained unclear. We aimed to compare the associations of indoor and outdoor temperature with ambulatory BP. Methods: From repeated measurements on two consecutive days during colder months (October–April) among 868 elderly individuals, we assessed the association of indoor and outdoor temperatures with ambulatory BP using multilevel analysis with random intercept for each individual. Results: Correlation between indoor and outdoor temperature got weak along with decreasing outdoor temperature. Outdoor temperature was not significantly associated with ambulatory BP. In contrast, a 1°C lower indoor temperature was significantly associated with 0.22 mmHg higher daytime SBP, 0.18% higher nocturnal BP fall, 0.34 mmHg higher sleep-trough morning BP surge independent of potential confounders including physical activity. The models with indoor temperature showed better fit of the model than those with outdoor temperature. Night-time SBP did not show significant association with indoor and outdoor temperature but with bed temperature. Discussion: Our results suggest the importance to assess the association of indoor temperature with cardiovascular mortality to determine whether improving housing thermal environment reduces winter excess mortality. Conclusion: Indoor temperature showed stronger association than outdoor temperature with BP in colder months.

Physiological Levels of Melatonin Relate to Cognitive Function and Depressive Symptoms: The HEIJO-KYO Cohort

CONTEXT In contrast with randomized controlled trials, observational studies have suggested that physiological levels of melatonin are reduced in patients with dementia or depression, but the relationship has not been evaluated in large populations. OBJECTIVE The objective was to determine the relationships between physiological levels of melatonin and cognitive function and depressive symptoms. DESIGN AND PARTICIPANTS A cohort of 1105 community-dwelling elderly individuals was enrolled in this cross-sectional study (mean age, 71.8 ± 7.1 y). MEASURES Urinary 6-sulfatoxymelatonin excretion (UME) and Mini-Mental State Examination (MMSE; n = 935) and Geriatric Depression Scale (GDS; n = 1097) scores were measured as indices of physiological melatonin levels, cognitive function, and depressive symptoms, respectively. RESULTS With increases in UME quartiles, the prevalence of cognitive impairment (MMSE score ≤ 26) and depressed mood (GDS score ≥ 6) significantly decreased (P for trend = .003 and .012, respectively). In multivariate logistic regression models, after adjusting for confounders such as age, gender, socioeconomic status, physical activity, and sleep/wake cycles, higher UME levels were significantly associated with lower odds ratios (ORs) for cognitive impairment and depressed mood (ORs: Q1 = 1.00; Q2 = 0.88 and 0.76; Q3 = 0.66 and 0.85; Q4 = 0.67 and 0.53; P for trend = .023 and .033, respectively). In addition, the highest UME group showed a significantly lower OR for depressed mood than the lowest UME group (Q4 vs Q1: OR, 0.53; 95% confidence interval, 0.32-0.89; P = .033). UME levels above the median value were significantly associated with a lower OR for cognitive impairment, even after further adjustment for depressive symptoms (OR = 0.74; 95% confidence interval, 0.55-0.99; P = .043). CONCLUSIONS Significant associations of higher physiological melatonin levels with lower prevalence of cognitive impairment and depressed mood were revealed in a large general elderly population. The association between physiological melatonin levels and cognitive function was independent of depressive symptoms.

Relationship between melatonin secretion and nighttime blood pressure in elderly individuals with and without antihypertensive treatment: a cross-sectional study of the HEIJO-KYO cohort

Circadian blood pressure variability and melatonin secretion are both regulated by the biological clock. Several clinical trials have suggested that oral administration of exogenous melatonin lowers blood pressure at night, although it remains unclear whether melatonin secretion, which is considerably lower than pharmacological melatonin levels, is associated with nighttime blood pressure. In this cross-sectional study, we measured overnight urinary melatonin excretion, which is an index of melatonin secreted, along with ambulatory blood pressure. Of 863 participants (mean age, 72.1 years), 386 participants received some form of antihypertensive drug treatment. With a quartile increase in urinary melatonin excretion, nighttime systolic blood pressure significantly decreased in the untreated group (P-value for trend=0.01), whereas neither association was observed in the treated group (P-value for trend=0.87). Among the untreated group, multivariate linear regression models revealed that higher log-transformed urinary melatonin excretion was significantly associated with decreased nighttime systolic blood pressure, independently of age, gender, body mass index, current smoking status, diabetes, daytime physical activity, duration in bed (scotoperiod) and day length (photoperiod) (regression coefficient: −2.21; 95% confidence interval: −4.38 to −0.05, P=0.045). This association suggests that an increase in the urinary melatonin excretion from 4.2 to 10.5 μg (25th to 75th percentile) is associated with a 2.0 mm Hg decrease in nighttime systolic blood pressure. In conclusion, melatonin secretion is significantly and inversely associated with nighttime blood pressure in a general elderly population without antihypertensive drug treatment. This association was not observed in treated elderly individuals.

The relationship between indoor, outdoor and ambient temperatures and morning BP surges from inter-seasonally repeated measurements

Higher morning blood pressure (BP) surge is a risk factor for cardiovascular disease independent of 24-h mean BP. Although low outdoor temperatures are associated with higher morning BP surges (MBPSs), the influence of indoor temperature and ambient temperatures (temperature while indoors or temperature while outdoors) on MBPS remains unclear. Such information may help prevent excess winter mortality. We simultaneously measured indoor temperatures (living room and bedroom), ambulatory BP and physical activity using wrist actigraphy for 768 person-days during winter and spring/fall in 192 participants (mean age, 69.9 years). Although the indoor and outdoor temperatures showed a strong correlation during periods of moderate temperature (range: 9.8 to 27.7 °C, rp=0.84), the correlation decreased during periods of lower outdoor temperatures (range: −3.37 to 9.73 °C, rp=0.28). In univariate and multivariate analyses, models with ambient temperatures showed the best goodness of fit (lowest Akaike’s information criterion (AIC)) followed by models with indoor temperatures and those with outdoor temperatures (AIC: ambient<indoor<outdoor temperature). A multivariate linear mixed-effect regression model showed that a 1 °C decrease in the ambient temperature was significantly associated with a 0.44 mm Hg increase in the sleep-trough MBPS and a 0.52 mm Hg increase in the prewaking BP surge. This was independent of potential confounders, including physical activity.

Lower Melatonin Secretion in Older Females: Gender Differences Independent of Light Exposure Profiles

Background Melatonin is associated with a variety of diseases in advanced age, including insomnia, depression, and dementia, and its secretion is influenced by light exposure. Although studies in young and middle-aged subjects have shown that females tend to have higher melatonin levels than males, gender differences in melatonin levels among older people remain unclear. Methods To determine the gender differences in melatonin levels among older people in home settings, we conducted a cross-sectional study in 528 older people. We measured overnight urinary 6-sulfatoxymelatonin excretion (UME; an index of melatonin secretion), and ambulatory light intensity. Results The mean age of females was 1.8 years younger, and average intensity of daytime light exposure was half that in males (P < 0.01). In a univariate comparison, UME was significantly lower in females than in males (P < 0.01). A multivariate model using analysis of covariance showed that log-transformed UME remained significantly lower in females after adjustment for potential confounding factors, including age and daytime and nighttime light exposure profiles (males vs. females: 1.90 vs. 1.73 log µg; adjusted mean difference 0.17 log µg [95% confidence interval [CI] 0.02–0.32]; P = 0.02). This result indicates that older females have 18.4% (95% CI, 2.2–37.4%) lower UME than older males. Conclusions Older females have significantly lower UME than older males, an association which is independent of light exposure profiles in home settings. Our findings may be useful as basic data for further research to investigate gender differences in several diseases associated with melatonin in the elderly.

Higher Cognitive Function in Elderly Individuals with Previous Cataract Surgery: Cross-Sectional Association Independent of Visual Acuity in the HEIJO-KYO Cohort

Cataract surgery improves visual acuity and drastically increases the capacity for light reception to the retina. Although previous studies suggested that both light exposure and visual acuity were associated with cognitive function, the relationships between cataract surgery, visual acuity, and cognitive function have not been evaluated in large populations. In this cross-sectional study, we measured cognitive function using the Mini-Mental State Examination and best-corrected visual acuity in pseudophakic (previous cataract surgery) and phakic (no previous cataract surgery) elderly individuals. Of 945 participants (mean age 71.7 years), 166 (17.6%) had pseudophakia and 317 (33.5%) had impaired cognitive function (score ≤26). The pseudophakic group showed significantly better visual acuity than the phakic group (p = 0.003) and lower age-adjusted odds ratio (ORs) for cognitive impairment (OR 0.66; p = 0.038). Consistently, in multivariate logistic regression models, after adjusting for confounding factors, including visual acuity and socioeconomic status, ORs for cognitive impairment were significantly lower in the pseudophakic group than in the phakic group (OR 0.64; 95% confidence interval 0.43-0.96; p = 0.031). This association remained significant in sensitivity analysis, excluding participants with low cognitive score ≤23 (n = 36). In conclusion, in a general elderly population, prevalence of cognitive impairment was significantly lower in pseudophakic individuals independently of visual acuity. The association was also independent of several major causes of cognitive impairment such as aging, gender, obesity, socioeconomic status, hypertension, diabetes, sleep disturbances, depressive symptoms, and physical inactivity.

The effect of blue-blocking intraocular lenses on circadian biological rhythm: protocol for a randomised controlled trial (CLOCK-IOL colour study)

Introduction Blue light information plays an important role in synchronising internal biological rhythm within the external environment. Circadian misalignment is associated with the increased risk of sleep disturbance, obesity, diabetes mellitus, depression, ischaemic heart disease, stroke and cancer. Meanwhile, blue light causes photochemical damage to the retina, and may be associated with age-related macular degeneration (AMD). At present, clear intraocular lenses (IOLs) and blue-blocking IOLs are both widely used for cataract surgery; there is currently a lack of randomised controlled trials to determine whether clear or blue-blocking IOLs should be used. Methods and analysis This randomised controlled trial will recruit 1000 cataract patients and randomly allocate them to receive clear IOLs or blue-blocking IOLs in a ratio of 1:1. The primary outcomes are mortality and the incidence of cardiovascular disease, cancer and AMD. Secondary outcomes are fasting plasma glucose, triglycerides, cholesterol, glycated haemoglobin, sleep quality, daytime sleepiness depressive symptoms, light sensitivity, the circadian rhythm of physical activity, wrist skin temperature and urinary melatonin metabolite. Primary outcomes will be followed until 20 years after surgery, and secondary outcomes will be assessed at baseline and 1 year after surgery. Ethics and dissemination Ethical approval has been obtained from the Institutional Review Board of Nara Medical University (No. 13-032). The findings of this study will be communicated to healthcare professionals, participants and the public through peer-reviewed publications, scientific conferences and the University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR) home page. Trial registration number UMIN000014680.

Comparisons of Objective Sleep Quality Between Elderly Individuals With and Without Cataract Surgery: A Cross-Sectional Study of the HEIJO-KYO Cohort

BACKGROUND Cataract surgery (CS) drastically increases the capacity for light reception to the retina. Several previous studies have suggested the beneficial effect of CS on subjectively measured sleep quality; however, the association between CS and objectively measured sleep quality remains uncertain. METHODS To evaluate the association between CS and objectively measured sleep quality in home settings, we conducted a cross-sectional study in 1037 elderly individuals (mean age, 71.9 years). We evaluated actigraphically measured sleep quality, urinary 6-sulfatoxymelatonin excretion, and ambulatory light levels, in addition to CS status. RESULTS The CS group (n = 174) showed significantly higher sleep efficiency and shorter wake after sleep onset than the no CS group (n = 863), even after adjustment for age, gender, body mass index, current smoking status, alcohol consumption, hypertension, diabetes, sleep medication, bedtime, rising time, daytime physical activity, daytime and nighttime light exposure, and urinary 6-sulfatoxymelatonin excretion (sleep efficiency: 85.8% in the CS group vs 84.4% in the no CS group, P = 0.042; wake after sleep onset: 45.7 min vs 50.6 min, respectively, P = 0.033). In contrast, urinary 6-sulfatoxymelatonin excretion, sleep onset latency, total sleep time, and sleep-mid time did not differ significantly between the CS and no CS groups. CONCLUSIONS Among a community-dwelling elderly population, CS is significantly associated with objectively measured sleep quality, but urinary levels of melatonin metabolite do not differ between individuals with and without CS. These associations are independent of daily light exposure profiles.

Relationship between breakfast skipping and obesity among elderly: Cross-sectional analysis of the HEIJO-KYO study

ObjectiveBreakfast skipping is reported to be associated with obesity in children and younger populations; however, few studies report the association among elderly. The purpose of this study was to investigate the relationships between breakfast skipping and obesity prevalence among elderly.DesignCross-sectional study.SettingCommunity-dwelling elderly in Nara, Japan.Participants1052 elderly participants (mean age: 71.6 years).MeasurementsObesity and breakfast skipping were defined as body mass index of ≥25 kg/m2 and skipping breakfast one or more times per week, respectively.ResultsTwo hundred and seventy-two participants (25.9%) were classified as obese and forty-one (3.9%) were as breakfast skippers. Obesity prevalence was significantly higher in breakfast skippers than in breakfast eaters (43.9% vs. 25.1%, P = 0.007). In multivariable logistic regression analysis adjusted for potential confounders (age, sex and alcohol consumption), breakfast skippers showed significantly higher odds ratio (OR) for obesity than breakfast eaters (OR, 2.23; 95% confidence interval, 1.17–4.27; P = 0.015), which continued to be significant after further adjustment for socioeconomic status. In addition, breakfast skippers showed significantly lower daily potassium (P <0.001) and dietary fibre intakes (P = 0.001) and lower subjective physical activity (P = 0.035) than breakfast eaters.ConclusionsBreakfast skipping was significantly associated with obesity among elderly. Poor diet quality and physical inactivity may be potential intermediators underlying the association between breakfast skipping and obesity.