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Body mass index, cognitive ability, and dementia: prospective associations and methodological issues in late life
Jönköping University, School of Health and Welfare, HHJ, Institute of Gerontology. Jönköping University, School of Health and Welfare, HHJ. Ageing - living conditions and health.
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aims of the present study were to investigate the association between overweight and cognitive ability and dementia, and to evaluate the usefulness of self-reported body mass index (BMI) in late life and various data sources commonly used in epidemiological studies to identify persons with dementia. Data were drawn from three population-based studies: the Swedish Adoption/Twin Study of Aging (SATSA), Aging in Women and Men: A Longitudinal Study of Gender Differences in Health Behaviour and Health among Elderly (the Gender Study), and the Finnish Lieto Study. In Study I, the agreement between self-reported and measured BMI over time was evaluated among 774 men and women, ages 40 to 88 years at baseline (mean age 63.9) participating in both the questionnaire phase and in-person testing of SATSA. Latent growth curve (LGC) modeling showed a small but significant increase between self-reported and measured BMI (0.02 kg/m2/y) over time, which would probably not affect the results if self-reported BMI were used as a continuous variable in longitudinal research. In Study II, the agreement between dementia diagnoses from various sources and dementia diagnoses set at a consensus conference was evaluated. Among the 498 elderly people ages 70 to 81 at baseline (mean age 74.5) enrolled in the Gender Study, 87 were diagnosed with dementia during an eight-year period. Review of medical records and nurse evaluations yielded the highest sensitivity (0.83 and 0.80, respectively) and a high specificity (0.98 and 0.96), indicating that these sources might be good proxies of dementia, while data extraction from the Swedish Inpatient Discharge Registry underestimated the prevalence of dementia (sensitivity 0.26). In Study III, the association between being overweight in midlife and cognitive ability in late life was examined in SATSA. The 781 participants ages 25 to 63 at baseline (mean age 41.6) in 1963 or 1973 self-reported their height and weight. From 1986 until 2002, they were assessed five times using a cognitive test battery. LGC models showed that people with higher midlife BMI scores had significantly lower cognitive ability and a significantly steeper decline than their thinner counterparts, an association that persisted when those who developed dementia during the study period were excluded from the analysis. This finding indicates that being overweight might affect cognitive ability independently of dementia. In Study IV, the association between BMI and dementia risk in older persons was described among 605 persons without dementia and ages 65 to 92 at baseline (mean age 70.8) in the Lieto Study. Among these, 86 persons were diagnosed with dementia during eight years of follow-up. Cox regression analyses indicated that for each unit increase in BMI score, the risk of dementia decreased 8% (hazard ratio = 0.92, 95% confidence interval = 0.87–0.97) and the association remained significant when individuals who developed dementia during the first four years of follow-up were excluded from the analyses. This result suggests that low BMI scores are present almost a decade before clinical dementia onset.

Place, publisher, year, edition, pages
Jönköping: Intellecta infolog , 2009. , p. 92
Series
Hälsohögskolans avhandlingsserie, ISSN 1654-3602 ; 7
Keywords [en]
aging, body mass index, cognition, dementia, epidemiology, longitudinal, population-based, prospective
National Category
Other Social Sciences not elsewhere specified
Identifiers
URN: urn:nbn:se:hj:diva-10283ISBN: 978-91-85835-06-5 (print)OAI: oai:DiVA.org:hj-10283DiVA, id: diva2:233987
Public defence
Forum Humanum, Hälsohögskolan, Barnarpsgatan 39, Jönköping (Swedish)
Opponent
Supervisors
Available from: 2009-09-04 Created: 2009-09-03 Last updated: 2016-09-12Bibliographically approved
List of papers
1. Identification of dementia in epidemiological research: A study on the usefulness of various data sources
Open this publication in new window or tab >>Identification of dementia in epidemiological research: A study on the usefulness of various data sources
2007 (English)In: Aging Clinical and Experimental Research, ISSN 1594-0667, E-ISSN 1720-8319, Vol. 19, no 5, p. 381-389Article in journal (Refereed) Published
Abstract [en]

Background and aims: Prevalence and incidence ratios of dementia in epidemiological studies vary according to the data source used. Medical records, cognitive tests, and registry information are sources frequently used to differentiate dementia from normal aging. The aim of the present study was to compare the identification of dementia from these different sources with that from consensus diagnosis. 

Methods: 498 elderly people (age range 70–81 at baseline) enrolled in a Swedish population-based longitudinal twin study (Gender) were evaluated on physical and mental health and interviewed for their socio-demographic background three times during an eight-year period. Reviews of medical records and the Swedish Discharge Registry (DR) were conducted. The 10th percentile was used to differentiate between dementia and non-dementia in all cognitive tests. Scores of 24 or below on the Mini-Mental State Examination (MMSE) (range 1–30) indicated dementia. A consensus conference diagnosed dementia on the basis of total information. The consensus diagnosis was used as the gold standard. 

Results: MMSE scores (sensitivity 64%, specificity 96%, kappa 0.65) and the review of medical records (sensitivity 57%, specificity 99%, kappa 0.65) were good sources for dementia identification. The precision of medical records increased when recordings of cognitive impairment were included (sensitivity 83%, specificity 98%, kappa 0.84). The discharge registry had low sensitivity (26%) and kappa coefficient (0.31). 

Conclusions: The present study shows that both review of medical records and MMSE scores are good although not perfect identifiers of dementia. The discharge registry is an uncertain source of dementia identification.

Place, publisher, year, edition, pages
Springer, 2007
Keywords
Cognitive tests; consensus; dementia; diagnosis; medical records
National Category
Other Social Sciences not elsewhere specified
Identifiers
urn:nbn:se:hj:diva-4280 (URN)10.1007/BF03324718 (DOI)000251732600007 ()18007116 (PubMedID)2-s2.0-37349072462 (Scopus ID)
Available from: 2007-11-02 Created: 2007-11-02 Last updated: 2019-04-09Bibliographically approved
2. Being overweight in midlife is associated with lower cognitive ability and steeper cognitive decline in late life
Open this publication in new window or tab >>Being overweight in midlife is associated with lower cognitive ability and steeper cognitive decline in late life
Show others...
2010 (English)In: The journals of gerontology. Series A, Biological sciences and medical sciences, ISSN 1079-5006, E-ISSN 1758-535X, Vol. 65A, no 1, p. 57-62Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Although an increasing body of evidence links being overweight in midlife with an increased risk for dementia in late life, no studies have examined the association between being overweight in midlife and cognitive ability in late life. Our aim was to examine the association between being overweight in midlife as measured by body mass index (BMI) and cognitive ability assessed over time. METHODS: Participants in the Swedish Adoption/Twin Study Aging were derived from a population-based sample. The participants completed baseline surveys in 1963 or 1973 (mean age 41.6 years, range 25-63 years). The surveys included questions about height, weight, diseases, and lifestyle factors. Beginning in 1986, the same individuals were assessed on neuropsychological tests every 3 years (except in 1995) until 2002. During the study period, 781 individuals who were 50 years and older (60% women) had at least one complete neuropsychological assessment. A composite score of general cognitive ability was derived from the cognitive test battery for each measurement occasion. RESULTS: Latent growth curve models adjusted for twinness showed that persons with higher midlife BMI scores had significantly lower general cognitive ability and significantly steeper longitudinal decline than their thinner counterparts. The association did not change substantially when persons who developed dementia during the study period were excluded from the analysis. CONCLUSIONS: Higher midlife BMI scores precede lower general cognitive ability and steeper cognitive decline in both men and women. The association does not seem to be mediated by an increased risk for dementia

Place, publisher, year, edition, pages
Oxford University Press, 2010
Keywords
cognition, old age, body mass index, epidemiology
National Category
Other Social Sciences not elsewhere specified
Identifiers
urn:nbn:se:hj:diva-8571 (URN)10.1093/Gerona/glp035 (DOI)000273115300008 ()19349594 (PubMedID)2-s2.0-74049088946 (Scopus ID)
Available from: 2009-04-22 Created: 2009-04-22 Last updated: 2019-04-09Bibliographically approved
3. Overweight and obesity in old age are not associated with greater dementia risk
Open this publication in new window or tab >>Overweight and obesity in old age are not associated with greater dementia risk
Show others...
2008 (English)In: Journal of The American Geriatrics Society, ISSN 0002-8614, E-ISSN 1532-5415, Vol. 56, no 12, p. 2261-2266Article in journal (Refereed) Published
Abstract [en]

OBJECTIVES: To describe the association between body mass index (BMI) and dementia risk in older persons.

DESIGN: Prospective population‐based study, with 8 years of follow‐up.

SETTING: The municipality of Lieto, Finland, 1990/91 and 1998/99.

PARTICIPANTS: Six hundred five men and women without dementia aged 65 to 92 at baseline (mean age 70.8).

MEASUREMENTS: Weight and height were measured at baseline and at the 8‐year follow‐up. Dementia was clinically assessed according to Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, criteria.

RESULTS: Eighty‐six persons were diagnosed with dementia. Cox regression analyses, adjusted for age, sex, education, cardiovascular diseases, smoking, and alcohol use, indicated that, for each unit increase in BMI score, the risk of dementia decreased 8% (hazard ratio (HR)=0.92, 95% confidence interval (CI)=0.87–0.97). This association remained significant when individuals who developed dementia early during the first 4 years of follow‐up were excluded from the analyses (HR=0.93, 95% CI=0.86–0.99). Women with high BMI scores had a lower dementia risk (HR=0.90, 95% CI=0.84–0.96). Men with high BMI scores also tended to have a lower dementia risk, although the association did not reach significance (HR=0.95, 95% CI=0.84–1.07).

CONCLUSION: Older persons with higher BMI scores have less dementia risk than their counterparts with lower BMI scores. High BMI scores in late life should not necessarily be considered to be a risk factor for dementia.

Place, publisher, year, edition, pages
John Wiley & Sons, 2008
Keywords
dementia; body mass index; population-based study; elderly
National Category
Geriatrics
Identifiers
urn:nbn:se:hj:diva-6617 (URN)10.1111/j.1532-5415.2008.01958.x (DOI)000261364100012 ()19093925 (PubMedID)2-s2.0-57149142096 (Scopus ID)
Available from: 2008-10-23 Created: 2008-10-23 Last updated: 2019-04-09Bibliographically approved

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