BMJ  2005;331:454-455 (20 August), doi:10.1136/bmj.331.7514.454-b

Letter

Obesity in middle age and future risk of dementia

Dietary fat and sugar may hold the clue

EDITOR—Whitmer et al report further evidence supporting the association between obesity and dementia.¹ Although the mechanism is still far from being understood, the authors alluded to the involvement of adiposity with inflammation and its markers.

One possible mechanism linking obesity with dementia is oxidative stress resulting from an increased intake of processed sugars and fats, which is the hall-mark of the modern diet. Rats maintained on a diet high in refined sugar and fat generated higher concentrations of free radicals.^{2 3} In contrast, caloric restriction in animals leads to reduced production of free radicals by mitochondria and increased longevity.⁴

Whitmer et al acknowledge that the lack of nutritional assessment was a limitation of their study. If such data had been available they would have shed light specifically on a possible relation between fat and sugar intake and risk of dementia, especially as a diet rich in these substances is linked to obesity. We recently showed that patients with dementia eating a diet high in fat and carbohydrates have an increased blood activity of glutathione peroxidase, an endogenous antioxidant, which may be a compensatory response to an increased oxidative stress in dementia.⁵

Whitmer et al say that all cause dementia diagnoses included dementia, Alzheimer's disease, and vascular dementia.¹ However, their data did not include differentiation between these subsets, especially between Alzheimer's disease and vascular dementia. Whether obesity was preferentially associated with either vascular dementia or Alzheimer's disease, or both, would be interesting, especially as the neuropathological aetiology of these two disorders is different.

Postgraduate Medical School, Faculty of Health, University of Brighton, Brighton BN1 9PH n.t.tabet{at}brighton.ac.uk

---

Competing interests: None declared.

References

1. Whitmer RA, Gunderson EP, Barrett-Connor E, Quesenberry CP, Yaffe K. Obesity in middle age and future risk of dementia: a 27 year longitudinal population based study. BMJ 2005;330: 1360-2. (11 June.)[Abstract/Free Full Text]
2. Hennig B, Slim R, Toborek M, Malecki A, Robertson LW. Effects of lipids and antioxidants on PCB-mediated dysfunction of vascular endothelial cells (EC). Central Eur J Public Health 2000;8: S18-9.
3. Kashiwagi A, Shinozaki K, Nishio Y, Okamura T, Toda N, Kikkawa R. Free radical production in endothelial cells as a pathogenetic factor vascular dysfunction in the insulin resistance state. Diabetes Res Clin Pract 1999;45: 199-203.[CrossRef][ISI][Medline]
4. Gredilla R, Barja G. The role of oxidative stress in relation to caloric restriction and longevity. Endocrinology 2005;26: Epub1-20.
5. Tabet N, Mantle D, Walker Z, Orrell M. Higher fat and carbohydrate intake in dementia patients is associated with increased blood glutathione peroxidase activity. Int Psychogeriatr 2005;17: 91-8.[Medline]

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

Relevant Article

Obesity in middle age and future risk of dementia: a 27 year longitudinal population based study

Rachel A Whitmer, Erica P Gunderson, Elizabeth Barrett-Connor, Charles P Quesenberry, Jr, and Kristine Yaffe
BMJ 2005 330: 1360. [Abstract] [Full Text] [PDF]