Evolving geriatric anthropometrics- an interplay with lifestyle changes, birth cohort effects, and survival implications. : Results from the general population study, “Good Aging in Skåne,” Sweden

Sammanfattning: There is a rising proportion of aging population worldwide. The high vulnerability of older adults to morbidity and mortality introduces an enormous health and economic burden to themselves and the society. The established leading cause of death among older adults is due to chronic and vascular diseases. These conditions are related to the nutritional status and are preventable with the help of accurate assessment for timely identification and adopting relevant lifestyle changes. Anthropometrics is an efficient and widely accepted method of body composition assessment. Body mass index (BMI), a commonly used measure of body fat has several well-known advantages and limitations. Despite the widespread awareness, very little attention is paid to the consequences of inaccurate BMI classification due to errors in height estimation, particularly among older adults due to aging-related degenerative changes. Consequent under- or false diagnosis of risk groups could seriously affect the designing of optimal health interventions. We need a holistic assessment including valid and accurate body composition estimation and accounting for extrinsic factors related to weight aberrations. The overall aim of this dissertation is to identify and address the methodological issues in anthropometric measurements in Swedish elderly population aged ≥60years and address the role of comorbidities, sociodemographics, lifestyle factors and cohort changes. The four studies in this thesis are based on data from the longitudinal nationally representative population study Good Aging in Skåne. Cross-sectional and follow-up study designs wereapplied. Descriptive statistics, analysis of variance tests and proportional hazard regression methods were adopted. Study I presented the sex- and age-specific normative anthropometric data for Swedish older adults. Comparison of theanthropometric profile in correlation with underlying comorbidities confirmed the association between cardiovascular diseases and adiposity and revealed a potential relationship between diminished functional capacity and inadequatephysical activity. Study II investigated the errors in BMI classification due to inaccurate height estimation among elderly. Age-adjusted and sex-specific BMI prediction equations based on knee-height and demispan estimates were formulated. Comparison between predicted and classic BMI classifications demonstrated a striking underestimation of underweight and overestimation of obesity, particularly alarming at the most vulnerable age of ≥80 years. Knee height predicted BMI on further investigation (study III) on the association with mortality risk identified a paradoxical survival benefit only among overweight older adults aged ≥80 years. Study IV examined the role of the birth cohort effects in waist circumference and its association with education and lifestyle factors of obesity. Older adults aged 60 years and 81 years having birth year 1952/54 and 1932/33 respectively had higher waist circumference and abdominal obesity that those born in 1941/43 and 1920/22 respectively. Waist gain was clearly influenced by higher educational attainment in the 60 year-olds, and by alcohol consumption and inadequate physical activity in 80-year-olds. Smoking prevalence and frequency of complete meal intake declined across the three birth cohorts from 2001─2013. Conclusions: Our study contributes to a holistic approach in the anthropometric assessment of body composition in elderly. It comprises: 1) A thorough description of the anthropometric profile of the population in relation to underlying medical conditions. 2) Application of proxy BMI to addressthe problems of misclassification from measurement errors, in relation to the paradoxical survival benefits of overweight only among the ‘older’ elderly and importantly 3) Account on the extrinsic factors that demonstrated encouraging patterns of educational attainment and diminishing sedentary living and warning signs from inadequate exercises in the ‘young’ elderly and increasing alcohol intake in the ‘old’ elderly. This calls for a broader action.