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Alzheimers Dement. 2018 May;14(5):601-609. doi: 10.1016/j.jalz.2017.09.016. Epub 2017 Nov 21.

Body mass index and risk of dementia: Analysis of individual-level data from 1.3 million individuals.

Author information

1
Department of Epidemiology and Public Health, University College London, London, UK; Clinicum, Department of Public Health, Faculty of Medicine, University of Helsinki, Helsinki, Finland; Finnish Institute of Occupational Health, Helsinki and Turku, Finland. Electronic address: m.kivimaki@ucl.ac.uk.
2
Clinicum, Department of Public Health, Faculty of Medicine, University of Helsinki, Helsinki, Finland.
3
Department of Epidemiology and Public Health, University College London, London, UK; Centre for Cognitive Ageing and Cognitive Epidemiology, Alzheimer Scotland Dementia Research Centre, University of Edinburgh, Edinburgh, UK.
4
School of Social and Community Medicine, University of Bristol, Bristol, UK.
5
Clinicum, Department of Public Health, Faculty of Medicine, University of Helsinki, Helsinki, Finland; Finnish Institute of Occupational Health, Helsinki and Turku, Finland.
6
Department of Epidemiology and Public Health, University College London, London, UK.
7
Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden; Centre for Occupational and Environmental Medicine, Stockholm County Council, Stockholm, Sweden.
8
Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden; School of Health Sciences and Welfare, Jönköping University, Jönköping, Sweden; Division of Epidemiology, Stress Research Institute, Stockholm University, Stockholm, Sweden.
9
Population-based Epidemiologic Cohort Unit, UMS 011, Inserm, Villejuif, France.
10
Department of Health Sciences, Mid Sweden University, Sundsvall, Sweden.
11
Division of Epidemiology, Stress Research Institute, Stockholm University, Stockholm, Sweden; Department of Psychology, Umeå University, Umeå, Sweden.
12
Folkhälsan Research Center, Folkhälsan, Helsinki, Finland; School of Health and Education, University of Skövde, Skövde, Sweden; Turku University Hospital, Turku, Finland.
13
Division of Epidemiology, Stress Research Institute, Stockholm University, Stockholm, Sweden.
14
Clinicum, Department of Public Health, Faculty of Medicine, University of Helsinki, Helsinki, Finland; Institute for Molecular Medicine (FIMM), University of Helsinki, Helsinki, Finland.
15
Occupational and Environmental Medicine, Uppsala University, Uppsala, Sweden.
16
Department of Neurobiology, Karolinska Institute, Stockholm, Sweden; National Institute for Health and Welfare, Helsinki, Finland.
17
Turku University Hospital, Turku, Finland; University of Turku, Turku, Finland.
18
Department of Epidemiology and Public Health, University College London, London, UK; Population-based Epidemiologic Cohort Unit, UMS 011, Inserm, Villejuif, France.
19
Institute of Behavioral Sciences, University of Helsinki, Helsinki, Finland.

Abstract

INTRODUCTION:

Higher midlife body mass index (BMI) is suggested to increase the risk of dementia, but weight loss during the preclinical dementia phase may mask such effects.

METHODS:

We examined this hypothesis in 1,349,857 dementia-free participants from 39 cohort studies. BMI was assessed at baseline. Dementia was ascertained at follow-up using linkage to electronic health records (N = 6894). We assumed BMI is little affected by preclinical dementia when assessed decades before dementia onset and much affected when assessed nearer diagnosis.

RESULTS:

Hazard ratios per 5-kg/m2 increase in BMI for dementia were 0.71 (95% confidence interval = 0.66-0.77), 0.94 (0.89-0.99), and 1.16 (1.05-1.27) when BMI was assessed 10 years, 10-20 years, and >20 years before dementia diagnosis.

CONCLUSIONS:

The association between BMI and dementia is likely to be attributable to two different processes: a harmful effect of higher BMI, which is observable in long follow-up, and a reverse-causation effect that makes a higher BMI to appear protective when the follow-up is short.

KEYWORDS:

Bias; Body mass index; Cohort study; Dementia; Obesity

PMID:
29169013
PMCID:
PMC5948099
DOI:
10.1016/j.jalz.2017.09.016
[Indexed for MEDLINE]
Free PMC Article

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