Inequality in physical activity, sedentary behaviour, sleep duration and risk of obesity in children: a 12-country study

OBJECTIVE

Studies examining associations between movement behaviours (i.e. physical activity, sedentary behaviour and sleep duration) and obesity focus on average values of these movement behaviours, despite important within-country and between-country variability. A better understanding of movement behaviour inequalities is important for developing public health policies and behaviour-change interventions. The objective of this ecologic analysis at the country level was to determine if inequality in movement behaviours is a better correlate of obesity than average movement behaviour volume in children from all inhabited continents of the world.

METHODS

This multinational, cross-sectional study included 6,128 children 9-11 years of age. Moderate-to-vigorous physical activity (MVPA), total sedentary time (SED) and sleep period time were monitored over 7 consecutive days using waist-worn accelerometry. Screen time was self-reported. Inequality in movement behaviours was determined using Gini coefficients (ranging from 0 [complete equality] to 1 [complete inequality]).

RESULTS

The largest inequality in movement behaviours was observed for screen time (Gini of 0.32; medium inequality), followed by MVPA (Gini of 0.21; low inequality), SED (Gini of 0.07; low inequality) and sleep period time (Gini of 0.05; low inequality). Average MVPA (h d-1) was a better correlate of obesity than MVPA inequality (r = -0.77 vs. r = 0.00, p = 0.03). Average SED (h d-1) was also a better correlate of obesity than SED inequality (r = 0.52 vs. r = -0.32, p = 0.05). Differences in associations for screen time and sleep period time were not statistically significant. MVPA in girls was found to be disproportionally lower in countries with more MVPA inequality.

CONCLUSIONS

Findings from this study show that average MVPA and SED should continue to be used in population health studies of children as they are better correlates of obesity than inequality in these behaviours. Moreover, the findings suggest that MVPA inequality could be greatly reduced through increases in girls' MVPA alone.

Enhancement of resistance in Mycobacterium lepraemurium infected C3H mice by treatment with sonicated M. lepraemurium or splenectomy

C3H mice were first infected in a hind footpad with 10(7) freshly harvested Mycobacterium lepraemurium bacilli. Four weeks later, when a granulomatous reaction was detected at the inoculation site, the animals were treated with two doses of a whole sonicated preparation of M. lepraemurium administered 2 weeks apart in the contralateral footpad. Such treatment was found to prolong the survival time of infected mice by 55-60 days. To study the involvement of the spleen in the immunomodulation of resistance to M. lepraemurium infection, splenectomy was performed in mice prior to infection via two different routes. Splenectomy significantly prolonged the mean survival time of mice infected in the footpad but did not affect survival of those infected intraperitoneally. Treatment of splenectomized footpad infected mice with sonicated bacilli abrogated almost completely the beneficial effect of splenectomy.

Role of adherent cells in graft-versus-host-induced suppression of the humoral immune response

Experiments were performed to investigate the role of adherent (A) cells in graft-versus-host (GVH)-induced immunosuppression. GVH reactions (GVHR) were induced in adult F1 hybrid mice by intravenous injections of parental lymphoid cells. Spleen cells (SC) from mice experiencing a GVHR (GVH mice) were stimulated with phytohaemagglutinin (PHA), concanavalin (Con A), and lipopolysaccharide (LPS). SC taken in the early phase of the GVHR (early GVHR) responded normally to LPS but did not respond to PHA and Con A. SC taken in an advanced phase of the GVHR (advanced GVHR) did not respond to PHA, Con A, or LPS. The influence of A cells from GVH mice (GVH-A cells) on the response of normal non-adherent cells to sheep erythrocytes (SRBC), PHA, and LPS was investigated. A cells from early GVHR, used in appropriate numbers, stimulated the responses to SRBC and to PHA; in excess they inhibited both responses. They had no effect on the response to LPS. A cells from advanced GVHR, even in low numbers, suppressed the responses to SRBC, PHA and LPS. The lymphoregulatory activities of GVH-A cells seemed to be mediated by soluble factors. The results indicate that the GVHR evokes complex non-specific regulatory interactions between A cells and lymphocytes.

[Role of adherent cells in GVH induced immunosuppression]

Two different mechanisms seem to be involved. In early GVH there is apparently an amplification of a normal inhibitory function of a cells. In more advanced GVH immunosuppression seem to be caused by a GVH induced suppressive activity of A cells. Both activities seem to be mediated by soluble factors.