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SUMMARYThis is an overview of epidemiology relevant to mental health problems in old age. We start by reviewing some basic terminology: the definitions of prevalence and incidence; the difference between descriptive and analytical epidemiology; the differences between study designs, including cross-sectional, case–control and cohort studies. We then cover the main epidemiological features of the major psychiatric diseases that affect older people (dementia and its different types, depression, late-onset schizophrenia, bipolar affective disorder, delirium, anxiety-related disorders, eating disorders, alcohol and substance misuse, personality disorders) and suicide.We end with some descriptive statistics regarding quality of life in older people.

It would appear that drugs for metastatic breast or colorectal cancer that extend, by a given amount, the time period between the start of treatment and disease progression (i.e., time to progression) have a strong tendency to extend, by roughly the same amount, the period between the start of treatment and death (i.e., overall survival).

SUMMARYAlzheimer's disease pathology accumulates years before the onset of clinical symptoms and has been termed ‘preclinical dementia’. Biomarkers have been developed to detect this pathology – namely, brain amyloid deposition and markers of neurodegeneration. In this article we describe these biomarkers and review the evidence for their clinical use in predicting risk both in the cognitively ‘normal’ and in those who already have established cognitive decline. We also discuss the limitations and ethical considerations of these tests and consider whether we should start incorporating Alzheimer's disease biomarkers into clinical practice. We find that, because many cognitively healthy people will have Alzheimer's pathology, and it is not clear whether this does help predict future risk of Alzheimer's disease, diagnosing preclinical dementia carries numerous ethical implications and is currently not being advocated outside research settings.LEARNING OBJECTIVES•Understand the concepts of preclinical and prodromal Alzheimer's disease and the use of biomarkers in this context•Analyse the supporting evidence for the use of biomarkers in prodromal and preclinical dementia•Apply this information to everyday clinical practiceDECLARATION OF INTERESTJ. C. H. works in the Research Institute for the Care of Older People (RICE), which undertakes clinical drug trials for drug companies. He is a sub-investigator on a number of trials (some of which involve neuroimaging and biomarkers) and principal investigator and chief investigator on two trials (neither of which involves biomarkers). All of these trials concern Alzheimer's disease or dementia. He does not receive any direct personal payment from the trials: the payment goes to RICE, which does, however, fund almost half of his post. RICE is an independent charity and separate from the University of Bristol.

This is a reflective essay about the time I spent volunteering in mental healthcare in Malawi, prior to commencing my psychiatry training. The burden of illness I saw was enormous and the resources very limited; however, I describe some particular experiences where we were able to deliver excellent care, and which made me reflect about mental health services in low-income countries in general. Details of the patients discussed in this essay have been fully anonymised.