Objective

To study the non-temporary effects of successive walks in forested areas (shinrin-yoku) on hypertension prevalence and blood pressure levels.

Methods

Data for the analysis were derived from the baseline survey of the Japan Multi-Institutional Collaborative Cohort (J-MICC) study in the Shizuoka area. Eligible participants were individuals aged 35–69 years who attended a health check-up center during 2006 and 2007. Of the 5,040 individuals who participated in the J-MICC study, Shizuoka, 4,666 were included in this analysis [3,174 men and 1,492 women; age (mean ± standard deviation) 52.1 ± 8.7 years]. The frequency of forest walking was estimated by a self-administrated questionnaire. Hypertension was defined as a systolic blood pressure ≥140 mmHg, a diastolic blood pressure ≥90 mmHg or, based on information provided in the questionnaire, the use of medication for hypertension.

Results

After adjusting for age, body mass index (BMI), smoking status, alcohol consumption, and habitual exercise, the odds ratios of hypertension associated with forest walking once a week or more frequently, relative to less than once a month were 0.98 in men [95% confidence interval (CI) 0.68–1.42] and 1.48 (95% CI 0.80–2.71) in women. There was no significant trend between adjusted blood pressure levels and the frequency of forest walking.

Conclusion

The results of our cross-sectional study in a Japanese population show no association between either blood pressure levels or the prevalence of hypertension and the frequency of forest walking.

Background

The aim of this study was to explore the associations between common potential functional promoter polymorphisms in pro-/anti-inflammatory cytokine genes and kidney function/chronic kidney disease (CKD) prevalence in a large Japanese population.

Methods

A total of 3,323 subjects aged 35-69 were genotyped for all 10 single nucleotide polymorphisms (SNPs) in the promoter regions of candidate genes with minor allele frequencies of > 0.100 in Japanese populations. The estimated glomerular filtration rate (eGFR) and CKD prevalence (eGFR < 60 ml/min/1.73 m2) of the subjects were compared among the genotypes.

Results

A higher eGFR and lower prevalence of CKD were observed for the homozygous variants of IL4 -33CC (high IL-4 [anti-inflammatory cytokine]-producing genotype) and IL6 -572GG (low IL-6 [pro-inflammatory cytokine]-producing genotype). Subjects with IL4 CC + IL6 GG showed the highest mean eGFR (79.1 ml/min/1.73 m2) and lowest CKD prevalence (0.0%), while subjects carrying IL4 TT + IL6 CC showed the lowest mean eGFR (73.4 ml/min/1.73 m2) and highest CKD prevalence (17.9%).

Conclusions

The functional promoter polymorphisms IL4 T-33C (rs2070874) and IL6 C-572G (rs1800796), which are the only SNPs that affect the IL-4 and IL-6 levels in Japanese subjects, were associated with kidney function and CKD prevalence in a large Japanese population.

Background

Sleep disturbance is a major health issue in Japan. This before-after study aimed to evaluate the immediate effects of forest walking in a community-based population with sleep complaints.

Methods

Participants were 71 healthy volunteers (43 men and 28 women). Two-hour forest-walking sessions were conducted on 8 different weekend days from September through December 2005. Sleep conditions were compared between the nights before and after walking in a forest by self-administered questionnaire and actigraphy data.

Results

Two hours of forest walking improved sleep characteristics; impacting actual sleep time, immobile minutes, self-rated depth of sleep, and sleep quality. Mean actual sleep time estimated by actigraphy on the night after forest walking was 419.8 ± 128.7 (S.D.) minutes whereas that the night before was 365.9 ± 89.4 minutes (n = 42). Forest walking in the afternoon improved actual sleep time and immobile minutes compared with forest walking in the forenoon. Mean actual sleep times did not increase after forenoon walks (n = 26) (the night before and after forenoon walks, 380.0 ± 99.6 and 385.6 ± 101.7 minutes, respectively), whereas afternoon walks (n = 16) increased mean actual sleep times from 342.9 ± 66.2 to 475.4 ± 150.5 minutes. The trend of mean immobile minutes was similar to the abovementioned trend of mean actual sleep times.

Conclusions

Forest walking improved nocturnal sleep conditions for individuals with sleep complaints, possibly as a result of exercise and emotional improvement. Furthermore, extension of sleep duration was greater after an afternoon walk compared to a forenoon walk. Further study of a forest-walking program in a randomized controlled trial is warranted to clarify its effect on people with insomnia.