Early life adversity and late life dementia in the Harmonised Cognitive Assessment Protocol network (U.S., China, England and Europe).

Social progress and medical advances since the last century have raised uneven global challenges. The Lancet commission on dementia released a recent estimate and projection of dementia: more than 57 million older adults today and nearly triple that number in 25 years, mostly in developing nations. Its life course frame is expansive on modifiable risk factors in mid and late life but restrained on early life. MATERIALS AND

methodsWe rectify this omission, assembling harmonised cognitive assessments from wealthy and developing nations (HCAP network) matched with retrospective childhood information obtained from 12,862 adults aged 69 years on average and 52% female. Error-laced recollection of early life adversity was analysed using latent construction and its association with cognitive status (normal, mild cognitive impairment/MCI and dementia) was estimated using multinomial logistic regression. Extensive sensitivity analyses were conducted. We plotted marginal probabilities of MCI and dementia for various groups. RESULTS AND DISCUSSION: Harmonised prevalence rates of MCI and dementia vary considerably. Early life adversity is found to be associated with late life MCI and dementia in England and Europe. Not so in China and U.S. where selective mortality throughout the life course in largely private health care systems may have played a prominent role. In England and Europe the relative risks of early life adversity on MCI are 1.50 (95% confidence interval 1.16 - 1.92) and on dementia 1.52 (1.12 - 2.06).These results uncover another manifestation of the life course shaping of health around the world, evidence made possible by harmonised methodologies which emerge as handy allies in global initiatives such as the UN Decade of Healthy Ageing. The analysis demonstrates that it is never too early to invest in healthy ageing.