Is maintaining or improving fitness key for dementia prevention?
Authors: Jari A Laukkanen, Setor K Kunutsor
Journal: The Lancet Public Health (2019)

Physical activity is associated with reduced risk of vascular and non-vascular outcomes and all-cause mortality.1Lee DC Pate RR Lavie CJ Sui X Church TS Blair SN Leisure-time running reduces all-cause and cardiovascular mortality risk.J Am Coll Cardiol. 2014; 64: 472-481Crossref PubMed Scopus (520) Google Scholar Objectively measured cardiorespiratory fitness, an index of physical activity, is an important marker of functional ability and cardiovascular health. Although cardiorespiratory fitness can be potentially comparable with smoking, hypertension, type 2 diabetes, and high cholesterol in predicting vascular disease and all-cause mortality outcomes,2Kodama S Saito K Tanaka S et al.Cardiorespiratory fitness as a quantitative predictor of all-cause mortality and cardiovascular events in healthy men and women: a meta-analysis.JAMA. 2009; 301: 2024-2035Crossref PubMed Scopus (2021) Google Scholar it is a risk factor that is not routinely measured in clinical settings.3Ross R Blair SN Arena R et al.Importance of assessing cardiorespiratory fitness in clinical practice: a case for fitness as a clinical vital sign. A scientific statement from the American Heart Association.Circulation. 2016; 134: e653-e699Crossref PubMed Scopus (1105) Google Scholar Accumulating evidence suggests that baseline levels of cardiorespiratory fitness are linked to a reduced risk of dementia. We present in the appendix studies showing association between cardiorespiratory fitness and risk of dementia. Owing to errors in measurements, lifestyle changes, chronic disease, and ageing, assessments using baseline measurements of an exposure could underestimate the true strength of an association between an exposure and disease outcome due to regression dilution bias. Our reproducibility substudies of cardiorespiratory fitness measurements within the Kuopio Ischemic Heart Disease prospective cohort study showed a within-person variability in cardiorespiratory fitness levels measured many years apart (regression dilution ratio 0·58).4Laukkanen JA Lavie CJ Khan H Kurl S Kunutsor SK Cardiorespiratory fitness and the risk of serious ventricular arrhythmias: a prospective cohort study.Mayo Clin Proc. 2019; 94: 833-841Summary Full Text Full Text PDF PubMed Scopus (21) Google Scholar This finding suggests that analyses using only single baseline measurements of cardiorespiratory fitness will underestimate associations with disease outcomes. Despite mounting evidence on the association between baseline levels of cardiorespiratory fitness and dementia risk, whether changes in cardiorespiratory fitness affect dementia risk is uncertain. In The Lancet Public Health, Atefe R Tari and colleagues5Tari AR Nauman J Zisko N et al.Temporal changes in cardiorespiratory fitness and risk of dementia incidence and mortality: a population-based prospective cohort study.Lancet Public Health. 2019; 4: e565-e574Summary Full Text Full Text PDF PubMed Scopus (40) Google Scholar report new evidence on temporal changes in estimated cardiorespiratory fitness and its association with dementia incidence and mortality, time of onset of dementia, and longevity after diagnosis in apparently healthy men and women at baseline. By use of the large-scale Norwegian Nord-Trøndelag Health Study (HUNT) cohort of 30 695 participants with repeat assessments of estimated cardiorespiratory fitness done 10 years after the baseline measurements, the authors show that participants who maintained or improved their estimated cardiorespiratory fitness values over time had substantially reduced risk of dementia incidence or mortality than did persistently unfit participants. Furthermore, participants who increased their estimated cardiorespiratory fitness over time gained 2·2 dementia-free years and 2·7 years of life. We applaud the authors for this new study which accounts for changes in estimated cardiorespiratory fitness over time, given its high within-person variability and robust study methods, and large sample size. A drawback of their study was their assessment of cardiorespiratory fitness, which was not based on the gold standard measure; ie, cardiopulmonary exercise testing with maximal oxygen uptake (VO2max) measured by ventilatory expired gas analysis.6Balady GJ Arena R Sietsema K et al.Clinician's guide to cardiopulmonary exercise testing in adults: a scientific statement from the American Heart Association.Circulation. 2010; 122: 191-225Crossref PubMed Scopus (1293) Google Scholar The authors used a non-exercise algorithm for estimating cardiorespiratory fitness, based on readily available clinical variables. Several of these non-exercise-based algorithms exist and can conveniently estimate cardiorespiratory fitness in a rapid, inexpensive, and reasonably accurate way when used for large population settings.3Ross R Blair SN Arena R et al.Importance of assessing cardiorespiratory fitness in clinical practice: a case for fitness as a clinical vital sign. A scientific statement from the American Heart Association.Circulation. 2016; 134: e653-e699Crossref PubMed Scopus (1105) Google Scholar The limitations of these non-exercise-based equations include underestimation and overestimation of cardiorespiratory fitness at the top and bottom ends of the distribution, respectively.3Ross R Blair SN Arena R et al.Importance of assessing cardiorespiratory fitness in clinical practice: a case for fitness as a clinical vital sign. A scientific statement from the American Heart Association.Circulation. 2016; 134: e653-e699Crossref PubMed Scopus (1105) Google Scholar and variability in assessment methodologies of the variables (eg, heart rate and physical activity) used to estimate cardiorespiratory fitness. Hence, not all equations are suitable for particular populations. A uniform definition of estimated cardiorespiratory fitness needs to be developed and validated so that results between studies are comparable. Although the use of cardiopulmonary exercise testing for defining cardiorespiratory fitness involves skills, equipment, and high costs (especially for large-scale settings), this method allows for the most accurate and standardised quantification of cardiorespiratory fitness.3Ross R Blair SN Arena R et al.Importance of assessing cardiorespiratory fitness in clinical practice: a case for fitness as a clinical vital sign. A scientific statement from the American Heart Association.Circulation. 2016; 134: e653-e699Crossref PubMed Scopus (1105) Google Scholar Finally, the authors' conclusions on the importance of assessing cardiorespiratory fitness in health risk assessment need to be interpreted with caution because no formal risk assessment analyses were done. The findings reported by Tari and colleagues5Tari AR Nauman J Zisko N et al.Temporal changes in cardiorespiratory fitness and risk of dementia incidence and mortality: a population-based prospective cohort study.Lancet Public Health. 2019; 4: e565-e574Summary Full Text Full Text PDF PubMed Scopus (40) Google Scholar are important and timely because they show that dementia risk could be decreased by maintaining or achieving a high age-relative estimated cardiorespiratory fitness, even after midlife. Dementia is a major public health burden especially with an ageing population.7Berr C Wancata J Ritchie K Prevalence of dementia in the elderly in Europe.Eur Neuropsychopharmacol. 2005; 15: 463-471Crossref PubMed Scopus (180) Google Scholar Although its pathogenesis is not fully understood, lifestyle factors, such as physical inactivity, smoking, unhealthy diet, and excessive alcohol, seem to play a part in its development. A physically active lifestyle promotes good cardiorespiratory fitness levels. However, most populations do not achieve levels recommended by established guidelines, which are 150–300 min per week of moderate intensity or 75–150 min per week of vigorous intensity aerobic physical activity or exercise for adults.8Piercy KL Troiano RP Ballard RM et al.The physical activity guidelines for Americans.JAMA. 2018; 320: 2020-2028Crossref PubMed Scopus (2244) Google Scholar Various strategies for promoting physical activity have been recommended, such as individual level-interventions, community-wide and school-based physical activity programmes, policy and environmental changes that improve access to physical activity, and information and communication technology, but levels are still low. Physical activity, exercise, or sports that are attractive to and feasible for the wider population, need to be identified to promote regular physical activity. Health professionals should use all opportunities to encourage their patients to be physically active. We declare no competing interests. Download .pdf (.22 MB) Help with pdf files Supplementary appendix Temporal changes in cardiorespiratory fitness and risk of dementia incidence and mortality: a population-based prospective cohort studyChange in estimated cardiorespiratory fitness is an independent risk factor for incidence dementia and dementia mortality. Maintaining or improving cardiorespiratory fitness over time may be a target to reduce risk of dementia incidence and mortality, delay onset, and increase longevity after diagnosis. Our data highlight the importance of assessing cardiorespiratory fitness in health risk assessment for people at risk of dementia. Full-Text PDF Open Access