Environmental risk factors for dementia are poorly understood. Aluminium and fluorine in drinking water have been linked with dementia but uncertainties remain about this relationship.

In the largest longitudinal study in this context, we set out to explore the individual effect of aluminium and fluoride in drinking water on dementia risk and, as fluorine can increase absorption of aluminium, we also examine any synergistic influence on dementia.

We used Cox models to investigate the association between mean aluminium and fluoride levels in drinking water at their residential location (collected 2005–2012 by the Drinking Water Quality Regulator for Scotland) with dementia in members of the Scottish Mental Survey 1932 cohort who were alive in 2005.

A total of 1972 out of 6990 individuals developed dementia by the linkage date in 2012. Dementia risk was raised with increasing mean aluminium levels in women (hazard ratio per s.d. increase 1.09, 95% CI 1.03–1.15, P < 0.001) and men (1.12, 95% CI 1.03–1.21, P = 0.004). A dose-response pattern of association was observed between mean fluoride levels and dementia in women (1.34, 95% CI 1.28–1.41, P < 0.001) and men (1.30, 95% CI 1.22–1.39, P < 0.001), with dementia risk more than doubled in the highest quartile compared with the lowest. There was no statistical interaction between aluminium and fluoride levels in relation with dementia.

Higher levels of aluminium and fluoride were related to dementia risk in a population of men and women who consumed relatively low drinking-water levels of both.

The relationship between the duration of depressive symptoms and mortality remains poorly understood.

To examine whether the duration of depressive symptoms is associated with mortality risk.

Data (n = 9560) came from the English Longitudinal Study of Ageing (ELSA). We assessed depressive symptom duration as the sum of examinations with an eight-item Center for Epidemiologic Studies Depression Scale score of ⩾3; we ascertained mortality from linking our data to a national register.

Relative to those participants who never reported symptoms, the age- and gender-adjusted hazard ratios for elevated depressive symptoms over 1, 2, 3 and 4 examinations were 1.41 (95% CI 1.15–1.74), 1.80 (95% CI 1.44–2.26), 1.97 (95% CI 1.57–2.47) and 2.48 (95% CI 1.90–3.23), respectively (P for trend <0.001). This graded association can be explained largely by differences in physical activity, cognitive function, functional impairments and physical illness.

In this cohort of older adults, the duration of depressive symptoms was associated with mortality in a dose–response manner.

That risk factors measured in middle age may not fully explain future dementia risk implicates exposures acting earlier in life. Height may capture early-life illness, adversity, nutrition and psychosocial stress.

To investigate the little-explored association between height and dementia death.

Individual participant meta-analysis using 18 prospective general population cohort studies with identical methodologies (1994–2008; n = 181 800).

Mean follow-up of 9.8 years gave rise to 426 and 667 dementia deaths in men and women respectively. The mean heights were 174.4cm (s.d. = 7.3) for men and 161.0cm (s.d. = 6.8) for women. In analyses taking into account multiple covariates, increasing height was related to lower rates of death from dementia in a dose–response pattern (P⩽0.01 for trend). There was evidence of a differential effect by gender (P = 0.016 for interaction). Thus, the association observed in men (hazard ratio per s.d. decrease in height 1.24, 95% CI 1.11–1.39) was markedly stronger than that apparent in women (HR = 1.13, 95% CI 1.03–1.24).

Early-life circumstances, indexed by adult height, may influence later dementia risk.

Life-course socioeconomic factors may have a role in dementia aetiology but there is a current paucity of studies. Meta-analyses of individual participant data would considerably strengthen this evidence base.

To examine the association between socioeconomic status in early life and adulthood with later dementia death.

Individual participant meta-analysis of 11 prospective cohort studies (1994–2004, n = 86508).

Leaving full-time education at an earlier age was associated with an increased risk of dementia death in women (fully adjusted hazard ratio (HR) for age ⩽14 v. age ⩾16: HR = 1.76, 95% Cl 1.23–2.53) but not men. Occupational social class was not statistically significantly associated with dementia death in men or women.

Lower educational attainment in women was associated with an increased risk of dementia-related death independently of common risk behaviours and comorbidities.

Inequality in health and treatment of disease across socioeconomic status groups is a major public health issue.

To examine differences in socioeconomic status in common mental disorders and use of psychotherapy provided by the public and private sector in the UK between 1991 and 2009.

During these years, 28 054 men and women responded to annual surveys by the nationally representative, population-based British Household Panel Survey (on average 7 measurements per participant; 207 545 person-observations). In each year, common mental disorders were assessed with the self-reported 12-item General Health Questionnaire and socioeconomic status was assessed on the basis of household income, occupational status and education.

Higher socioeconomic status was associated with lower odds of common mental disorder (highest v. lowest household income quintile odds ratio (OR) 0.88, 95% CI 0.82–0.94) and of being treated by publicly provided psychotherapy (OR = 0.43, 95% CI 0.34–0.55), but higher odds of being a client of private psychotherapy (OR = 3.33, 95% CI 2.36–4.71). The status difference in publicly provided psychotherapy treatment was more pronounced at the end of follow-up (OR = 0.36, 95% CI 0.23–0.56, in 2005–2009) than at the beginning of the follow-up period (OR =0.96, 95% CI 0.66–1.39, in 1991–1994; time interaction P<0.001). The findings for occupational status and education were similar to those for household income.

The use of publicly provided psychotherapy has improved between 1991 and 2009 among those with low socioeconomic status, although social inequalities in common mental disorders remain.

Patient overcrowding and violent assaults by patients are two major problems in psychiatric healthcare. However, evidence of an association between overcrowding and aggressive behaviour among patients is mixed and limited to small-scale studies.

This study examined the association between ward overcrowding and violent physical assaults in acute-care psychiatric in-patient hospital wards.

Longitudinal study using ward-level monthly records of bed occupancy and staff reports of the timing of violent acts during a 5-month period in 90 in-patient wards in 13 acute psychiatric hospitals in Finland. In total 1098 employees (physicians, ward head nurses, registered nurses, licensed practical nurses) participated in the study. The outcome measure was staff reports of the timing of physical assaults on both themselves and ward property.

We found that 46% of hospital staff were working in overcrowded wards, as indicated by >10 percentage units of excess bed occupancy, whereas only 30% of hospital personnel were working in a ward with no excess occupancy. An excess bed occupancy rate of >10 percentage units at the time of an event was associated with violent assaults towards employees (odds ratio (OR) = 1.72, 95% CI 1.05–2.80; OR = 3.04, 95% CI 1.51–6.13 in adult wards) after adjustment for confounding factors. No association was found with assaults on ward property (OR = 1.06, 95% CI 0.75–1.50).

These findings suggest that patient overcrowding is highly prevalent in psychiatric hospitals and, importantly, may increase the risk of violence directed at staff.

Prospective data on the association between common mental disorders and obesity are scarce, and the impact of ageing on this association is poorly understood.

To examine the association between common mental disorders and obesity (body mass index 30 kg/m2) across the adult life course.

The participants, 6820 men and 3346 women, aged 35–55 were screened four times during a 19-year follow-up (the Whitehall II study). Each screening included measurements of mental disorders (the General Health Questionnaire), weight and height.

The excess risk of obesity in the presence of mental disorders increased with age (P = 0.004). The estimated proportion of people who were obese was 5.7% at age 40 both in the presence and absence of mental disorders, but the corresponding figures were 34.6% and 27.1% at age 70. The excess risk did not vary by gender or according to ethnic group or socioeconomic position.

The association between common mental disorders and obesity becomes stronger at older ages.

Risk factors for homicide are emerging; however, the predictive value of IQ, for which there is a strong prima facie case, has yet to be examined.

To examine the association between IQ and risk of death by homicide.

A cohort of 968 846 men, aged 18–19 years, were administered an IQ test battery at military conscription and then followed for mortality experience over two decades.

There were 191 deaths due to homicide during follow-up. In age-adjusted analyses, a high total IQ test score was associated with a reduced rate of homicide (hazard ratio (HR) per standard deviation increase in IQ score=0.49, 95% CI 0.42–0.57). A step-wise gradient was apparent across the three IQ groups (P-value for trend 50.001). After adjustment for indicators of socio-economic position and illness at conscription, this gradient was marginally attenuated (HR=0.57, 95% CI 0.49–0.67).

High IQ test scores in early adulthood were associated with a reduced risk of death by homicide.