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- Mitnitski, Arnold, et al.
(författare)
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A cross-national study of transitions in deficit counts in two birth cohorts: implications for modeling ageing.
- 2007
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Ingår i: Experimental gerontology. - : Elsevier BV. - 0531-5565. ; 42:3, s. 241-6
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Tidskriftsartikel (refereegranskat)abstract
- Generally, health does not improve with age, and many physical and physiological functions are known to decline. These changes do not occur uniformly, however; for many reasons, some people experience significant improvement in their health over non-trivial time intervals. Earlier, we showed that 5-year transitions in health status in elderly people (age 65+ years) can be modeled as a stochastic process, using a modified Poisson distribution with four readily interpretable parameters. The original description was based on follow-up of a single cross-sectional study, thus mixing age and cohort effects. Here, we again used a multistate Markov chain to model 5-year deficit accumulation in relation to frailty in both a Swedish birth cohort (aged 70 years at inception) and, from the original cross-sectional study, a Canadian birth cohort, aged 69-71. In both datasets, we found again that a modified Poisson describes the transition in health status with high precision. The parameters of the model though different, are close to each other, even though the cohorts are from different countries, were assembled 20 years apart, and counted different deficits. The model suggests that all health transitions, including health improvement, worsening, and death, can be summarized in a unified stochastic model with a few interpretable parameters.
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| 4. |
- Tajar, Abdelouahid, et al.
(författare)
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Frailty in Relation to Variations in Hormone Levels of the Hypothalamic-Pituitary-Testicular Axis in Older Men: Results From the European Male Aging Study.
- 2011
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Ingår i: Journal of the American Geriatrics Society. - : Wiley. - 0002-8614. ; 59:5, s. 814-821
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To explore the associations between frailty and reproductive axis hormones (as an important regulatory system) in middle aged and older men. DESIGN: Cross-sectional. SETTING: The European Male Aging Study. PARTICIPANTS: Three thousand two hundred nineteen community-dwelling European men aged 40 to 79. MEASUREMENTS: Interviewer-assisted questionnaires to assess physical activity, health status, and mood were administered. Testosterone (T), luteinizing hormone (LH), follicle-stimulating hormone (FSH), dehydroepiandrosterone sulfate (DHEAS), and sex hormone-binding globulin (SHBG) were measured in a fasting morning blood sample. Frailty was assessed as an index (FI) according to the number (out of 43 possible) of health deficits (symptoms, signs, and functional impairments). Relationships between FI and hormone levels (as outcomes) were explored using regression models. RESULTS: Mean FI was 0.12 ± 0.11 (range 0-0.67) was highest in the oldest group. After adjustment for confounders, higher levels of FI were significantly associated with lower levels of total T, free T, and DHEAS and higher levels of gonadotropins and SHBG; a 1-standard deviation cross-sectional increase in FI was associated with a regression coefficient of -0.30 nmol/L (95% confidence interval (CI)=-0.53 to -0.07) decrease in total T and 0.66 U/L (95% CI=0.48-0.83) increase in LH. CONCLUSIONS: The associations between high FI, high gonadotropins, and well-maintained circulating T suggest that these changes are markers of aging-related disruptions of multiple physiological regulation, of which alterations in pituitary-testicular function represent a sensitive marker rather than an underlying pathogenic mechanism for frailty.
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