Takeaway
- This meta-analysis provides no evidence to support a paradox on beneficial effects of overweight and obesity in older age on incident dementia.
- Long-term follow-up studies are required to explain the association of body weight with the risk of dementia in older age.
Why this matters
- Majority of dementia cases occur in older age, with over 90% of those developing after age >60 years and 32% in those ≥85 years.
- Findings from previous studies have been limited due to the combining of middle- and older-aged adults in the samples for analysis.
Study design
- 16 studies with follow-up periods ranging between 3 and 18 years (38,219 participants and 4479 patients with dementia) met eligibility criteria after a search on Embase, Medline, PubMed, CINAHL, Psych-info and Cochrane library databases.
- Funding: None disclosed.
Key results
- Pooled data from 15 studies (including new data from China) of the relative risk (RR) of dementia in relation to continuous body mass index (BMI) showed a non-significant risk reduction (RR, 0.97; 95% CI, 0.94-1.00; P=.055).
- Further analysis stratified by duration of study follow-up showed that the RR of dementia was 0.95 (95% CI, 0.92-0.97) for <9 years and 1.00 (95% CI, 0.93-1.08) for ≥9 years.
- Compared with combined normal and underweight BMI categories, RR of dementia in older people classified as overweight and obese was 0.98 (95% CI, 0.54-1.77) and 1.17 (95% CI, 0.65-2.10), respectively (n=5 studies).
- No association between increased waist circumference (WC) and reduced risk for dementia was observed (large WC: RR, 1.04; 95% CI, 0.90-1.20 and larger WC: RR, 0.94; 95% CI, 0.80-1.09).
Limitations
- Sex-stratified analysis to examine any gender differences not performed.
References
References