Persistence of Low Back Pain and Predictive Ability of Pain Intensity and Disability in Daily Life among Nursery School Workers in Japan: A Five-Year Panel Study.

Nursery school workers are known for having a high prevalence of low back pain (LBP). The natural history of LBP and the determinants of persistent LBP remain unclear. We examined the prevalence of persistent LBP and whether pain intensity and disability in daily life due to LBP affected the persistence of LBP among these workers. A five-year panel study was conducted for 446 nursery school workers in Japan. LBP, pain intensity, and disability in daily life due to LBP were assessed with a self-administered questionnaire survey. Pain intensity was assessed using the numerical rating scale (NRS). The Roland-Morris Disability Questionnaire (RDQ) was used to assess disability in daily life due to LBP. At baseline, 270 nursery school workers (60.5%) suffered from LBP. The estimated prevalence of persistent LBP was 84.6% (80.3-88.9%), 82.2% (77.7-86.8%), and 82.0% (77.4-86.5%) at 1, 3, and 5 years after the initial study, respectively. NRS scores of 5 or greater predicted the persistence of LBP at 1 and 3 years after the initial survey (adjusted odds ratios: 4.01 (1.27-12.6) and 8.51 (1.87-38.7), respectively), while RDQ scores did not. In conclusion, LBP highly persisted for a long time and pain intensity predicted persistent LBP among nursery school workers in Japan.

Psychosocial work characteristics and low back pain in daycare (nursery) workers in Japan: a prospective cohort study.

BACKGROUND: Low back pain (LBP) is one of the most common musculoskeletal problems affecting daycare (nursery) workers. We aimed to identify the psychosocial factors influencing LBP in daycare workers. METHODS: We conducted a prospective cohort study with a one-year observation period. The baseline sample was a convenience sample of 444 daycare workers from 34 daycare facilities in Nagoya, Japan, and its suburbs. All the data were collected through a questionnaire survey. The question "Where are you currently feeling LBP?" was used to determine whether the subjects suffered from LBP. We examined the prospective relationships of the psychosocial work characteristics, i.e., high job strain, low social support, effort-reward imbalance, and overcommitment, at baseline and LBP after one year. We used multiple logistic regression analyses to calculate the odds ratios of psychosocial work characteristics for the persistence and onset of LBP, adjusted for age, sex, body mass index, smoking, employment status, occupation, and working schedule. RESULTS: At baseline, 270 (60.8%) subjects suffered from LBP. Of 208 who also gave information on LBP one year later, 176 (84.6%) suffered from the persistence of LBP. Low social support at baseline was significantly related to persistent LBP one year later. The incidence of persistent LBP was 89.9% and 80.0% among those with and without low social support at baseline, respectively. The adjusted odds ratio (95% confidence interval) of low social support at baseline for the persistence of LBP was 2.43 (1.01-5.87). Of 150 who were without LBP at baseline and provided information on LBP one year later, 45 (30.0%) suffered from the onset of LBP. None of the psychosocial work characteristics showed significant relationships with the onset of LBP one year later. CONCLUSION: Low social support was related to the persistence, but not to the onset of LBP in a prospective cohort analysis among daycare workers in Japan. High job strain, ERI, or overcommitment did not show a significant prospective effect on LBP.

Activation of adiponectin receptors has negative impact on muscle mass in C2C12 myotubes and fast-type mouse skeletal muscle.

This study investigated the effects of AdipoRon, which is an agonist for adiponectin receptor 1 (AdipoR1) and AdipoR2, on the protein content, myotube diameter, and number of nuclei per myotube of C2C12 cells and skeletal muscle mass in C57BL/6J mice. AdipoRon suppressed the protein content, myotube diameter, and number of nuclei per myotube of C2C12 cells of C2C12 myotubes in a dose-dependent manner. Adiponectin-associated decline of protein content, diameter, and number of nuclei per myotube in C2C12 myotubes was partially rescued by knockdown of AdipoR1 and/or AdipoR2. Phosphorylation level of AMPK showed a trend to be increased by AdipoRon. A significant increase in phosphorylation level of AMPK was observed at 20 µM AdipoRon. Knockdown of AdipoR1 and/or AdipoR2 rescued AdipoRon-associated decrease in protein content of C2C12 myotubes. AdipoRon-associated increase in phosphorylation level of AMPK in C2C12 myotubes was suppressed by knockdown of AdipoR1 and/or AdipoR2. Successive intravenous injections of AdipoRon into mice caused a decrease in the wet weight of plantaris muscle (PLA), but not in soleus muscle (SOL). Mean fiber cross-sectional area of PLA, but not of SOL, was significantly decreased by AdipoRon administration. On the one hand, the expression level of phosphorylated AMPK and ubiquitinated protein in SOL and PLA muscles was upregulated by AdipoRon administration. On the other hand, AdipoRon administration induced no changes in the expression level of puromycin-labeled proteins in both SOL and PLA muscles. Expression level of adiponectin in extensor digitorum longus (EDL) muscle was increased by aging, but not in SOL muscle. Aging had no effect on the expression level of AdipoR1 and AdipoR2 in both muscles. Phosphorylation level of AMPK in EDL was increased by aging, but not SOL muscle. Results from this study suggest that high level of circulating adiponectin may induce skeletal muscle atrophy, especially fast-type muscle.

Nuclear Accumulation of HSP70 in Mouse Skeletal Muscles in Response to Heat Stress, Aging, and Unloading With or Without Reloading.

The purpose of this study was to investigate the nuclear accumulation of heat shock protein 70 (HSP70), a molecular chaperonin in mouse skeletal muscle in response to aging, heat stress, and hindlimb unloading with or without reloading. Profiles of HSP70-specific nuclear transporter Hikeshi in skeletal muscles were also evaluated. Heat stress-associated nuclear accumulation of HSP70 was observed in slow soleus (SOL) and fast plantaris (PLA) muscles of young (10-week-old) mice. Mean nuclear expression level of HSP70 in slow medial gastrocnemius (MGAS) and PLA muscles of aged (100-week-old) mice increased ~4.8 and ~1.7 times, compared to that of young (10-week-old) mice. Reloading following 2-week hindlimb unloading caused accumulation of HSP70 in myonuclei in MGAS and PLA of young mice ( p < 0.05). However, reloading-associated nuclear accumulation of HSP70 was not observed in both types of muscles of aged mice. On the other hand, 2-week hindlimb unloading had no impact on the nuclear accumulation of HSP70 in both muscles of young and aged mice. Nuclear expression level of Hikeshi in both MGAS and PLA in mice was suppressed by aging. No significant changes in the nuclear Hikeshi in both muscles were induced by unloading with or without reloading. Results of this study indicate that the nuclear accumulation of HSP70 might show a protective response against cellular stresses in skeletal muscle and that the protective response may be suppressed by aging. Protective response to aging might depend on muscle fiber types.