Testing decaying dark matter models as a solution to the S8S_8 tension with the thermal Sunyaev-Zel'dovich effect

Considering possible solutions to the $S_8$ tension between the Planck cosmic microwave background (CMB) measurement and low-redshift probes, we extended the standard $\Lambda$CDM cosmological model by including decay of dark matter (DDM). We first tested the DDM model in which dark matter decays into a form of noninteracting dark radiation. Under this DDM model, we investigated the impacts of DDM on the Sunyaev Zel'dovich (SZ) effect by varying the decay lifetime, $\Gamma^{-1}$, including the background evolution in cosmology and the nonlinear prescription in the halo mass function. We performed a cosmological analysis under the assumption of this extended cosmological model by combining the latest high-redshift Planck CMB measurement and low-redshift measurements of the SZ power spectrum as well as the baryonic acoustic oscillations (BAO) and luminosity distances to type Ia supernovae (SNIa). Our result shows a preference for $\Gamma^{-1} \sim 220$ Gyr with a lower bound on the decay lifetime of $\sim$ 38 Gyr at 95\% confidence level. Additionally, we tested the other DDM model in which dark matter decays into warm dark matter and dark radiation. This model supports $\Gamma^{-1} \sim 137$ Gyr to resolve the $S_8$ tension with a lower bound on the decay lifetime of $\sim$ 24 Gyr at 95\% confidence level. Comparing these two models, we find that the second leads to slightly better reconciliation of the $S_8$ tension.Comment: 9 pages, 5 figures, Accepted for publication in A&

Convolutional neural network-reconstructed velocity for kinetic SZ detection

We report the detection of the kinetic Sunyaev-Zel'dovich (kSZ) effect in galaxy clusters with a 4.9 sigma significance using the latest 217 GHz Planck map from data release 4. For the detection, we stacked the Planck map at the positions of 30,431 galaxy clusters from the Wen-Han-Liu (WHL) catalog. To align the sign of the kSZ signals, the line-of-sight velocities of galaxy clusters were estimated with a machine-learning approach, in which the relation between the galaxy distribution around a cluster and its line-of-sight velocity was trained through a convolutional neural network. To train our network, we used the simulated galaxies and galaxy clusters in the Magneticum cosmological hydrodynamic simulations. The trained model was applied to the large-scale distribution of the Sloan Digital Sky Survey galaxies to derive the line-of-sight velocities of the WHL galaxy clusters. Assuming a standard beta-model for the intracluster medium, we obtained the gas mass fraction in R500 to be fgas,500 = 0.09 +- 0.02 within the galaxy clusters with the average mass of M500 ~ 1.0 x 10^14 Msun/h.Comment: 8 pages, 6 figures. arXiv admin note: text overlap with arXiv:2007.0295

Association between sarcopenia and low back pain in local residents prospective cohort study from the GAINA study

[Background] Low back pain (LBP) is one of the most common ailments that people experience in their lifetime. On the other hands, Sarcopenia also leads to several physical symptoms and contributes to reducing the quality of life of elderly people.The purpose of this study is to investigate the association between sarcopenia and low back pain among the general population. [Methods] The subjects included 216 adults (79 men and 137 women; mean age, 73.5 years) undergoing a general medical examination in Hino, Japan. Skeletal muscle index (SMI), The percentage of young adults’ mean (%YAM) of the calcaneal bone mass using with quantitative ultrasound (QUS) method and walking speed were measured, and subjects who met the criteria of the Asian Working Group for Sarcopenia were assigned to the sarcopenia group. Subjects with decreased muscle mass only were assigned to the pre-sarcopenia group, and all other subjects were assigned to the normal group. Then, we compared the correlations with low back pain physical finding. The Oswestry Disability Index (ODI) and the low back pain visual analogue scale (VAS) were used as indices of low back pain. Statistical analysis was performed among three groups with respect their characteristic, demographics, data of sarcopenia determining factor, VAS and ODI. We also analysed prevalence of LBP and sarcopenia. We investigated the correlations between ODI and the sarcopenia-determining factors of walking speed, muscle mass and grip strength. [Results] Sarcopenia was noted in 12 subjects (5.5%). The pre-sarcopenia group included 38 subjects (17.6%), and the normal group included 166 subjects (76.9%). The mean ODI score was significantly higher in the sarcopenia group (25.2% ± 12.3%; P < 0.05) than in the pre-sarcopenia group (11.2% ± 10.0%) and the normal group (11.9% ± 12.3%). %YAM and BMI were significantly lower in the sarcopenia group than in other groups (P < 0.05). A negative correlation existed between walking speed and ODI (r = −0.32, P < 0.001). [Conclusions] The results of this study suggested that decreased physical ability due to quality of life in residents with LBP may be related to sarcopenia

The Risk Factor of Worsening Low Back Pain in Older Adults Living in a Local Area of Japan: The GAINA Study

Background: Several factors, particularly osteoporosis, obesity, and a lack of exercise, contribute to low back pain (LBP). This observational longitudinal cohort study to identify the risk factors for worsening low back pain. Methods: We sent a self-administered questionnaire and a consent form for this study to 1,450 subjects aged > 40 years in Hino, Japan. Baseline assessments of 273 individuals undergoing medical check-ups were conducted from 2014 to 2016. The subjects were divided into Group A (no change or improvement in LBP) and Group B (worsening LBP). LBP was assessed using a visual analog scale; body mass index (BMI), bone mineral density, skeletal muscle index (SMI), standing posture, and habitual exercise frequency were also evaluated. We defined, habitual exercise as nontherapeutic exercise (e.g. swimming, walking, physical exercise and work out). Results: Overall, 81.2% subjects performed habitual exercise in Group A, a greater number of subjects than the 40.8% in Group B. BMI, SMI, and bone mineral density (BMD) were not significantly different between the two groups. Lack of exercise was a significant risk factor for worsening of LBP. On the other hand, the lack of osteoporosis treatment was significantly different between subjects with worsening LBP despite habitual exercise and those who did not perform habitual exercise. Conclusion: Although habitual exercise is useful to prevent LBP, it may not necessarily be useful for those with a lack of osteoporosis treatment. Although exercise is typically posited to prevent LBP, it may not be effective in preventing LBP associated with osteoporosis

Relationship among Osteoporosis, Sarcopenia, Locomotive Syndrome, and Spinal Kyphosis in Older Individuals Living in a Local Mountain Area

Study Design Cross-sectional cohort study. Purpose This study investigated the relationship among osteoporosis, sarcopenia, locomotive syndrome, and spinal kyphosis in older individuals living in a mountain area. Overview of Literature Kyphosis greatly reduces the quality of life of older individuals. Osteoporosis and sarcopenia are kyphosis-causing factors. Methods This cross-sectional study included 361 individuals aged ≥65 years (mean age, 75.0 years) living in a local mountain area and underwent medical check-ups from 2014 to 2018. The survey items included kyphosis index, body mass index, back pain prevalence, back pain Visual Analog Scale score, Oswestry Disability Index, walking speed, grip strength, skeletal mass index, osteoporosis (% young adult mean [YAM]), LOCOMO 5 score, and presence of sarcopenia (Asian Working Group for Sarcopenia). The participants were divided into the N (kyphosis index: <12; n=229, 63.4%), M (kyphosis index: 12–15; n=99, 27.4%), and K (kyphosis index: ≥15; n=33, 9.2%) groups. p-values of <0.05 were considered statistically significant. An association factor of kyphosis (kyphosis index: ≥15) was investigated with logistic regression analysis. Results Age and LOCOMO 5 scores were significantly higher (p<0.05) and %YAM and walking speed were significantly lower (p<0.05) in the K group than in the M and N groups. Other survey items showed significant differences. Only %YAM (odds ratio, 0.20; 95% confidence interval, 0.04–0.96) was an independent factor associated with a kyphosis index of ≥15. Conclusions Decreased muscle mass and muscle strength would be related to kyphosis; however, no such relations were noted. Bone loss was significantly related to kyphosis. Osteoporosis-induced decrease in vertebral body height is present in the background. Sarcopenia and locomotive syndrome were not related to kyphosis, whereas decreased bone density was independently associated with kyphosis in older individuals living in a mountain area