Reader response: Midlife cardiovascular fitness and dementia
MikaKivimäki, Professor, University College London (London, UK)
JaanaPentti, Statistician, University of Helsinki (Helsinki, Finland)
ArchanaSingh-Manoux, Research director, INSERM (Paris, France)
Submitted March 19, 2018
Hörder et al. advanced the hypothesis that midlife cardiovascular fitness protects against old-age dementia. [1] However, the limitations of the data were not fully discussed. The estimated benefit of greater fitness in terms of dementia prevention is overoptimistic. Using data from Tables 3 and 4 in the paper, [1] we calculated a population attributable fraction (PAF) of 78.3%, suggesting that 8 of 10 dementia cases would be avoided if all women had high cardiovascular fitness (see Table). This is more than 2 times greater than the collective PAF for all known modifiable risk factors in the most recent synopsis, [2] which is itself an upper-bound estimate. [3]
Due to the small number of dementia cases, the results reported by Hörder et al. are unlikely to be robust. There were only 2 dementia cases in the high fitness group; 2 additional cases would lead to a PAF < 60% whereas 2 fewer cases would lead to the conclusion that women with high fitness do not develop dementia at all. The finding by Hörder et al. [1] is also unlikely to be an "underestimate" as suggested by the accompanying editorial. [4] Results based on 2 cases could be entirely due to chance.
1. Hörder H, Johansson L, Guo X, et al. Midlife cardiovascular fitness and dementia: A 44-year longitudinal population study in women. Neurology Epub 2018 Mar 14.
2. Livingston G, Sommerlad A, Orgeta V, et al. Dementia prevention, intervention, and care. Lancet 2017;390:2673-734.
3. Kivimäki M, Singh-Manoux A. Prevention of dementia by targeting risk factors. Lancet (in-press 2018).
4. Spartano NL, Ngandu T. Fitness and dementia risk: Further evidence of the heart-brain connection. Neurology Epub 2018 Mar 14.
For disclosures, please contact the editorial office at [email protected].
Hörder et al. advanced the hypothesis that midlife cardiovascular fitness protects against old-age dementia. [1] However, the limitations of the data were not fully discussed. The estimated benefit of greater fitness in terms of dementia prevention is overoptimistic. Using data from Tables 3 and 4 in the paper, [1] we calculated a population attributable fraction (PAF) of 78.3%, suggesting that 8 of 10 dementia cases would be avoided if all women had high cardiovascular fitness (see Table). This is more than 2 times greater than the collective PAF for all known modifiable risk factors in the most recent synopsis, [2] which is itself an upper-bound estimate. [3]
Due to the small number of dementia cases, the results reported by Hörder et al. are unlikely to be robust. There were only 2 dementia cases in the high fitness group; 2 additional cases would lead to a PAF < 60% whereas 2 fewer cases would lead to the conclusion that women with high fitness do not develop dementia at all. The finding by Hörder et al. [1] is also unlikely to be an "underestimate" as suggested by the accompanying editorial. [4] Results based on 2 cases could be entirely due to chance.
1. Hörder H, Johansson L, Guo X, et al. Midlife cardiovascular fitness and dementia: A 44-year longitudinal population study in women. Neurology Epub 2018 Mar 14.
2. Livingston G, Sommerlad A, Orgeta V, et al. Dementia prevention, intervention, and care. Lancet 2017;390:2673-734.
3. Kivimäki M, Singh-Manoux A. Prevention of dementia by targeting risk factors. Lancet (in-press 2018).
4. Spartano NL, Ngandu T. Fitness and dementia risk: Further evidence of the heart-brain connection. Neurology Epub 2018 Mar 14.
For disclosures, please contact the editorial office at [email protected].