| Background and Objective: Globally,the aging process will lead to a significant increase in the number of patients with dementia.As one of the most common chronic diseases among elderly people,dementia will not only seriously reduce the quality of life of elderly patients,but also would bring heavy economic burden and life pressure to patients' families and society.Dementia is incurable till nowadays.It is indicated that drugs commonly used in the treatment of dementia could only improve the symptoms of dementia and delay the progress of the disease to some extent.At the same time a lot of studies have also found that there are a lot of factors are the onset of dementia or induced cognitive function.Studies found that early-life environment related to childhood brain development and cognitive function in later life.However,studies on early-life risk factors for dementia were still controversial.For example,some studies indicated that there is an association between body growth and later risk of dementia while several cross-sectional studies failed to identify this relationship.The purpose of our study is to identify reliable risk factors in early life.Identifying early-life risk factors for dementia is specifically significant for constructing a lifelong framework for preventing dementia or cognitive decline.Although these risk factors are difficult to eliminate completely,moderate improvement can also have a significant impact on the incidence of dementia.Methods: We searched English literature published in PubMed and Cochrane libraries from 1 January 1865 to 1 June 2017,and included prospective studies and retrospective case-control studies on exploring early-life factors for dementia and cognitive impairment.Literatures were included when they met the following criteria simultaneously: 1)the study design is a prospective cohort or retrospective case-control study;and 2)the study objective is to identify the early-life(?18 years old)risk factors for dementia.If it was difficult to determine whether an article should be included,another investigator would help to make the final decision.Pooled effect estimates for each factor was calculated according to the random-effect model.If there were over 10 studies for the same factor,we tend to complete the test of publication bias with STATA software.Results: Thirty-seven studies with 46,727 participants were included.The pooled results indicated significant associations of dementia with food deficiency(OR= 2.05,95% CI= 1.22-3.44),low education level(RR= 1.80,95% CI= 1.60-2.02),and shorter leg length(OR= 1.19,95% CI= 1.07-1.32).Other potential risk factors for dementia in later life identified in the systematic review include adverse family-related factors,history of head trauma,poor intelligence and learning ability.Adverse family-related factors include rural residence,the characteristics of father‘s job,number of siblings(?5),early parental death or re-marriage.Conclusion: Early-life risk factors for dementia include low education level,food deficiency,shorter leg length,history of head trauma,adverse family-related factors,poor intelligence and learning ability.Those factors might were associated with the cognitive and brain reserve to increase the risk of dementia in later life.Further high-quality longitudinal studies needed to verify the causality between early-life risk factors and dementia and cognitive impairment. |
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