Date Published: May 1, 2018
Publisher: Elsevier, Inc
Author(s): Mika Kivimäki, Ritva Luukkonen, G. David Batty, Jane E. Ferrie, Jaana Pentti, Solja T. Nyberg, Martin J. Shipley, Lars Alfredsson, Eleonor I. Fransson, Marcel Goldberg, Anders Knutsson, Markku Koskenvuo, Eeva Kuosma, Maria Nordin, Sakari B. Suominen, Töres Theorell, Eero Vuoksimaa, Peter Westerholm, Hugo Westerlund, Marie Zins, Miia Kivipelto, Jussi Vahtera, Jaakko Kaprio, Archana Singh-Manoux, Markus Jokela.
•Data from 1.3 million adults from 39 prospective cohort studies were pooled for the analyses.•Higher BMI was associated with increased risk of dementia when the follow-up was long.•When follow-up was short, lower BMI was linked to increased dementia risk probably due to reverse causation.
The costs of dementia are enormous and increasing globally . Current clinical guidelines for dementia prevention view obesity as one of the modifiable risk factors , , but the evidence is based on a relatively limited number of observational studies and the findings are mixed , , , , , , , , . The most recent meta-analysis, including 4 studies and 16,282 participants, suggested a 1.4-fold increased risk of dementia in the obese . The largest study in the field, published after the inclusion date for the meta-analysis, found no increase in dementia incidence among the obese . On the contrary, higher body mass index (BMI) was linked to lower dementia risk.
Descriptive characteristics for each cohort study are provided in Appendix 1. The weighted mean follow-up across studies was 16.1 years and ranged from 4.3 to 37.7 years. Over the 21,798,141 person-years at risk in 1,349,857 participants, 6894 incident dementia cases were recorded. Overall, we observed an inverse association between BMI and dementia. The age-, sex-, and ethnicity-adjusted hazard ratio per 5-unit increase in BMI was 0.87 (95% CI = 0.82–0.93). An I2 statistic of 65.9% indicated significant heterogeneity in the study-specific hazard ratios (P < .0001). To further examine this association, we undertook four sets of analyses. In this collaborative study of over 1.3 million adults from Europe, the United States, and Asia, higher BMI was associated with increased dementia risk when weight was measured >20 years before dementia diagnosis, but this association was reversed when BMI was assessed <10 years before dementia diagnosis. Source: http://doi.org/10.1016/j.jalz.2017.09.016