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Physical inactivity, cardiometabolic disease, and risk of dementia: an individual-participant meta-analysis

BMJ 2019; 365 doi: (Published 17 April 2019) Cite this as: BMJ 2019;365:l1495

Linked BMJ Opinion

Reflections on null findings: the case of physical activity and risk of dementia

Dementia and zinc, magnesium and B vitamin deficiencies Re: Physical inactivity, cardiometabolic disease, and risk of dementia: an individual-participant meta-analysis

The IPD-Work consortium did not find that dementia related to physical activity. 1 However excessive physical activity can cause magnesium deficiency in red blood cells and muscle damage although serum magnesium levels can be normal. 2 Dementia is most commonly related to zinc, magnesium and B vitamin deficiencies as the number of references in PubMed for dementia and separate nutritional deficiencies are:

3143 references for zinc deficiency
2530 for vitamin B12 deficiency
1638 for vitamin B6 deficiency
1449 for folic acid deficiency
1245 for magnesium deficiency
1177 for vitamin D deficiency
193 PUFA deficiencies

Monitored repletion of essential nutrient deficiencies should be more widely available, especially zinc levels in white blood cells and functional tests for B vitamin deficiencies. It is safer and more physiological to supplement B12 deficiency with methylcobalamin rather than cyanocobalamin.

There is also at least moderate evidence implicating increases in environmental risk factors: air pollution, aluminium, silicon, selenium, pesticides and electric and magnetic fields, as risk factors for dementia. 3

In 1989 we reported in the BMJ that all of the dyslexic children tested were zinc deficient in their sweat (measured to parts per billion) although their serum zinc levels were in the normal range. Age and sex matched control children had sweat and serum zinc levels in the normal range. 4,5

It is important that dementia and learning difficulties are most commonly related to zinc and B vitamin deficiencies.

1 Kivimäki M, Singh-Manoux A, Pentti J, Sabia S, Nyberg ST, Alfredsson L, Goldberg M, Knutsson A, Koskenvuo M, Koskinen A, Kouvonen A, Nordin M, Oksanen T, Strandberg T, Suominen SB, Theorell T, Vahtera J, Väänänen A, Virtanen M, Westerholm P, Westerlund H, Zins M, Seshadri S, Batty GD, Sipilä PN, Shipley MJ, Lindbohm JV, Ferrie JE, Jokela M; IPD-Work consortium. Physical inactivity, cardiometabolic disease, and risk of dementia: an individual-participant meta-analysis. BMJ 2019; 365: l1495.

2 Howard J. Muscle Action, Trace Elements and Related Nutrients: The Myothermogram. In: Chazot G, Abdulla M, Arnaud P, eds. Current Trends in Trace Element Research: Proceedings of International Symposium on Trace Elements. Paris, 1987, Smith-Gordon, London,1989, pp79-85.

3 Killin LOJ. Starr JM, Shiue IJ, RussTC, Environmental risk factors for dementia: a systematic review. BMC Geriatr. 2016; 16: 175. Published online 2016 Oct 12. doi: 10.1186/s12877-016-0342-y

4 Grant ECG, Howard JM, Davies S, Chasty H, Hornsby B, Galbraith J. Zinc deficiency in children with dyslexia: concentrations of zinc and other minerals in sweat and hair. BMJ 1989;296:607-609.

5 Howard JMH. Serum, Leucocyte, Sweat and Hair Zinc Levels - a correlational Study. J.Nutr.Med. 1990;1:119-126.

Competing interests: No competing interests

24 April 2019
Ellen CG Grant
Physician and medical gynaecologist
Kingston-upon-Thames, KT2 7JU