Objectives Detection of dementia is essential for improving the lives of patients but the extent of underdetection worldwide and its causes are not known. This study aimed to quantify the prevalence of undetected dementia and to examine its correlates. Methods/setting/participants A systematic search was conducted until October 2016 for studies reporting the proportion of undetected dementia and/or its determinants in either the community or in residential care settings worldwide. Random-effects models calculated the pooled rate of undetected dementia and subgroup analyses were conducted to identify determinants of the variation. Primary and secondary outcome measures The outcome measures of interest were the prevalence and determinants of undetected dementia. Results 23 studies were eligible for inclusion in this review. The pooled rate of undetected dementia was 61.7% (95% CI 55.0% to 68.0%). The rate of underdetection was higher in China and India (vs Europe and North America), in the community setting (vs residential/nursing care), age of <70 years, male gender and diagnosis by general practitioner. However, it was lower in the studies using Mini-Mental State Examination (MMSE) diagnosis criteria. Conclusions The prevalence of undetected dementia is high globally. Wide variations in detecting dementia need to be urgently examined, particularly in populations with low socioeconomic status. Efforts are required to reduce diagnostic inequality and to improve early diagnosis in the community.

Global risks of suicidal behaviours (SB) and being bullied as well as their association among adolescents have been poorly understood. We aimed to determine the risks of suicidal ideation (SI), suicide planning (SP), suicide attempt (SA) and being bullied in adolescents and their related associations across gender, countries and different WHO regions. We examined data from the Global School-based Health Survey (GSHS), which recorded health behaviours among adolescents aged 12 to 15 years from 83 countries. We computed prevalence rates of SB and being bullied and their 95% confidence intervals (CIs). Multilevel models were employed to examine the association of being bullied with risks of SI, SP and SA. The overall prevalence of SI was 16·5%, SP 16·5%, SA 16·4%, and being bullied 35·3%. The highest risks of SB and being bullied were in Africa (SI 19·9%, SP 23·2%, SA 20·8%, being bullied 48·0%). Compared to boys, girls had an increased risk for SI (18·2%) and SP (17·3%) but similar risk for SA (16·7%) and being bullied (33·3%). Being bullied was associated with SA (adjusted odds ratio ‒ aOR 2·14, 95%CI 2·06-2·23), more strongly than SI (1·83, 1·78-1·89) and SP (1·70, 1·65-1·76). The strongest association with SA was in the Western Pacific (2·68, 2·45-2·92) and with SI (2·04, 1·74-2·39) and SP (1·81, 1·68-1·95) were in Southeast Asia. There were no gender differences in aOR for SI and SP, but the aOR for SA among boys (2·28, 2·14-2·42) was significantly greater than among girls (2·04, 1·93-2·15), ratio of two odds ratios was 1.12 (P = 0.008). SB and being bullied were common among adolescents worldwide. The findings of gender differences in SB, being bullied and their association could inform the design of prevention programmes to reduce the risks of SI, SP and SA in adolescents worldwide.

Background: It is unclear whether overweight and obesity in older age reduces or increases the risk of incident dementia. Objective: To assess the impacts of overweight and obesity in older age on incident dementia. Methods: We searched cohort studies reporting body weight measured in older age and dementia through PubMed, Embase, Medline, PyschInfo, and Cochrane library until July 2016. Sixteen articles were identified for the review. We pooled data from them and a new unpublished study from China, to calculate relative risk (RR) of incident dementia in relation to body mass index (BMI) and waist circumference (WC). Results: All 16 cohort studies were undertaken in high income countries, with follow-up periods ranging between 3 to 18 years. Thirteen studies showed an inverse association between BMI and dementia, and three studies demonstrated a positive association. Pooled RR of dementia in relation to continuous BMI from 14 studied populations, including the new Chinese data, was 0.97 (95% CI 0.95–1.00); in those followed up <9 years it was 0.95 (0.93–0.96) while in ≥9 years follow-up it was 1.03 (0.96–1.11). In five studied populations examining categorical BMI, RR of dementia in older people classified as overweight and obese was 0.98 (0.54–1.77) and 1.17 (0.65–2.10) respectively, in comparison with other weights. The pooled WC data showed no association between increased WC and reduced risk of dementia. Conclusion: The current evidence did not support a paradox on beneficial impacts of overweight and obesity in older age on incident dementia. More studies with long term follow up are needed to clarify the association of body weight in older age with dementia risk.