Cohort profile: The Vitality 90+ Study-a cohort study on health and living conditions of the oldest old in Tampere, Finland.

PURPOSE: Vitality 90+ is an ongoing population-based study with repeated cross-sectional data collections. The study was designed to examine trends in health, functioning, living conditions, quality of life and care needs among the oldest old in Finland. PARTICIPANTS: Nine mailed surveys have been conducted in the city of Tampere between 1995 and 2018. The first three surveys in 1995, 1996 and 1998 included all community-dwelling individuals aged 90 years or older; and the following six surveys in 2001, 2003, 2007, 2010, 2014 and 2018 covered all individuals in Tampere regardless of their living arrangements. In total, the surveys have included 5935 participants (8840 observations). Around 80% of the participants have been women. The participants' age range has been between 90 and 107 years. FINDINGS TO DATE: The surveys have consistently asked the same questions over time, covering basic sociodemographic factors, morbidity, functioning, self-rated health (SRH), living arrangements, social relations, quality of life, care needs and providers of care. Survey data have been linked with national register data on health and social service use, mortality and medication. The main findings regarding the time trends show an increase in the proportion of people independent in activities of daily living and mobility. Along with improved functioning, the number of chronic conditions has increased, and SRH has shown a tendency to decline. In addition, we have found increasing occupational class inequalities in functioning and SRH over time. FUTURE PLANS: The next round of data collection will be completed by the end of 2022. The Vitality 90+ Study welcomes research collaborations that fall within the general aims of the project. The research data 1995-2014 are archived at the Finnish Social Science Data Archive and the data for years 2018 and 2022 will be archived in 2023.

A Polygenic Risk Score for Hand Grip Strength Predicts Muscle Strength and Proximal and Distal Functional Outcomes among Older Women.

PURPOSE: Hand grip strength (HGS) is a widely used indicator of overall muscle strength and general health. We computed a polygenic risk score (PRS) for HGS and examined whether it predicted muscle strength, functional capacity, and disability outcomes. METHODS: Genomewide association study summary statistics for HGS from the Pan-UK Biobank was used. PRS were calculated in the Finnish Twin Study on Aging ( N = 429 women, 63-76 yr). Strength tests included HGS, isometric knee extension, and ankle plantarflexion strength. Functional capacity was examined with the Timed Up and Go, 6-min and 10-m walk tests, and dual-task tests. Disabilities in the basic activities of daily living (ADL) and instrumental ADL (IADL) were investigated with questionnaires. The proportion of variation in outcomes accounted for by PRS HGS was examined using linear mixed models and extended logistic regression. RESULTS: The measured HGS increased linearly over increasing PRS ( ß = 4.8, SE = 0.93, P < 0.001). PRS HGS independently accounted for 6.1% of the variation in the measured HGS ( ß = 14.2, SE = 3.1, P < 0.001), 5.4% of the variation in knee extension strength ( ß = 19.6, SE = 4.7, P < 0.001), 1.2% of the variation in ankle plantarflexion strength ( ß = 9.4, SE = 4.2, P = 0.027), and 0.1%-1.5% of the variation in functional capacity tests ( P = 0.016-0.133). Further, participants with higher PRS HGS were less likely to have ADL/IADL disabilities (odds ratio = 0.74-0.76). CONCLUSIONS: Older women with genetic risk for low muscle strength were significantly weaker than those with genetic susceptibility for high muscle strength. PRS HGS was also systematically associated with overall muscle strength and proximal and distal functional outcomes that require muscle strength.

Type 2 Diabetes as a Predictor of Muscle Strength Decline over 11 years among Men and Women Aged 55 Years and Older.

BACKGROUND: Long-term associations between type 2 diabetes, prediabetes, and muscle strength are obscure in older adults. The aim of this study was to examine type 2 diabetes as a predictor of handgrip strength decline during an 11-year follow-up among men and women aged 55 years. METHODS: We used Finnish population-based Health 2000 Survey and its follow-up measurements in 2011. The study population consisted of 1,200 individuals, aged 55-86 years at baseline. Baseline fasting glucose level or use of diabetes medication was used to categorize the participants into diabetes (≥7.0 mmol/L), prediabetes (≥6.1 mmol/L but <7.0 mmol/L), and nondiabetes (<6.1 mmol/L) groups. Handgrip strength was measured at baseline and during 11-year follow-up. RESULTS: Mean handgrip strength at baseline did not differ between diabetes groups in men or women. Among men during the 11-year follow-up, decline in muscle strength was significantly greater among diabetes group (-131.5 Newtons [N], 95% confidence interval (CI) -182.7 to -80.4) than nondiabetes group (-98.9 N, 95% CI -139.5 to -58.3) after adjusting for age, education, lifestyle factors, chronic conditions, and diabetes status at follow-up. Among women, muscle strength decline did not differ between diabetes, prediabetes, or nondiabetes groups after adjusting for all potential covariates, the results being -45.0 N (95% CI -73.2 to -16.7), -29.4 N (95% CI -59.7 to 0.9), and -42.3 N (95% CI -70.5 to -14.1), respectively. CONCLUSIONS: The presence of type 2 diabetes was associated with greater muscle strength decline among older men but not among older women.

Trends of Physical Functioning, Morbidity, and Disability-Free Life Expectancy Among the Oldest Old: Six Repeated Cross-Sectional Surveys Between 2001 and 2018 in the Vitality 90+ Study.

BACKGROUND: It remains unclear whether increasing longevity is accompanied by a compression or expansion of poor health and disability. We examined trends of physical functioning and morbidity in a population aged 90 and older, and disease- and disability-free life expectancy (LE) at age 90 between 2001 and 2018 in Finland's third most populated city. METHODS: We used survey data from the Vitality 90+ Study, which comprises a series of six repeated mailed surveys (7,590 observations). Information on mortality came from Statistics Finland. We examined trends of functioning (activities of daily living [ADL] and mobility) and cardiovascular and dementia morbidity using age-adjusted generalized estimating equation models stratified by sex. In addition, age-, sex-, and period-specific health expectancies were calculated using Sullivan's method. RESULTS: Over time, functioning improved, especially, in women, and morbidity increased in men. From 2001 to 2018, LE at age 90 increased by 5.3 months for men and 6.4 months for women. LE without ADL disability increased by 5.0 months for men and 8.4 months for women, and LE without mobility disability by 6.0 months for men and 4.4 months for women. LE without cardiovascular and dementia morbidity decreased for men (2.6 months) and increased for women (1.9 months). CONCLUSIONS: In relative terms, we found a compression of disability for both sexes and an expansion of morbidity for men. Although the trends overall are rather positive, the increase in absolute morbidity and, to some extent, in disability will inevitably mean increasing care needs with population aging.

Educational Differences in Decline in Maximum Gait Speed in Older Adults Over an 11-Year Follow-up.

BACKGROUND: This study examined educational differences in decline in maximum gait speed over an 11-year follow-up in the general Finnish population aged 55 years and older and assessed the contribution of lifestyle factors, body mass index, physical workload, and chronic conditions on the association. METHOD: Data from the nationally representative Health 2000 Survey and its 11-year follow-up were used. Participants aged 55 years and older with maximum gait speed measured at both time points were included (n = 1128). Information on education, age, sex, lifestyle factors, body mass index, physical workload, and chronic conditions was collected at baseline. General linear model was used to examine differences in decline in maximum gait speed between education groups. Mediation analyses using the product method was conducted to partition the total effect of education on decline in maximum gait speed into direct effect and indirect effect acting through mediators. RESULTS: Decline in maximum gait speed was greater in low and intermediate education groups in comparison to the high education group (0.24 m/s [95% confidence interval 0.21-0.26], 0.24 m/s [0.21-0.28], 0.10 m/s [0.07-0.14], respectively]. The most important mediators were higher body mass index and lifetime exposure to physical workload among the less educated, accounting for 10% and 11% of the total effect, respectively. CONCLUSIONS: Education-based disparities in objectively measured mobility increase with age as lower education is associated with greater decline in gait speed. Higher body mass index and physical workload among less educated contributed most to the educational disparities in age-related decline in maximum gait speed.

Longitudinal change in physical functioning and dropout due to death among the oldest old: a comparison of three methods of analysis.

Longitudinal studies examining changes in physical functioning with advancing age among very old people are plagued by high death rates, which can lead to biased estimates. This study was conducted to analyse changes in physical functioning among the oldest old with three distinct methods which differ in how they handle dropout due to death. The sample consisted of 3992 persons aged 90 or over in the Vitality 90+ Study who were followed up on average for 2.5 years (range 0-13 years). A generalized estimating equation (GEE) with independent 'working' correlation, a linear mixed-effects (LME) model and a joint model consisting of longitudinal and survival submodels were used to estimate the effect of age on physical functioning over 13 years of follow-up. We observed significant age-related decline in physical functioning, which furthermore accelerated significantly with age. The average rate of decline differed markedly between the models: the GEE-based estimate for linear decline among survivors was about one-third of the average individual decline in the joint model and half the decline indicated by the LME model. In conclusion, the three methods yield substantially different views on decline in physical functioning: the GEE model may be useful for considering the effect of intervention measures on the outcome among living people, whereas the LME model is biased regarding studying outcomes associated with death. The joint model may be valuable for predicting the future characteristics of the oldest old and planning elderly care as life expectancy continues gradually to rise.

Body Mass Index and Waist Circumference as Predictors of Disability in Nonagenarians: The Vitality 90+ Study.

BACKGROUND: Only scarce data exist on the association between obesity and disability in the oldest old. The purpose of this prospective study is to examine if body mass index and waist circumference (WC) are associated with incident mobility and activities of daily living (ADL) disability in nonagenarians. METHODS: We used longitudinal data from the Vitality 90+ Study, which is a population-based study conducted at the area of Tampere, Finland. Altogether 291 women and 134 men, aged 90-91 years, had measured data on body mass index and/or WC and did not have self-reported mobility or ADL disability at baseline. Incident mobility and ADL disability was followed-up on median 3.6 years (range 0.6-7.8 years). Mortality was also followed-up. Multinomial logistic regression models were used for the analyses, as death was treated as an alternative outcome. The follow-up time was taken into account in the analyses. RESULTS: Neither low or high body mass index, nor low or high WC, were associated with incident mobility disability. In women, the lowest WC tertile (<82 cm) was associated with an increased probability of incident ADL disability when compared to the middle WC tertile (odds ratio 3.98, 95% CI 1.35-11.77). CONCLUSIONS: Obesity is not associated with incident mobility or ADL disability in nonagenarians. Instead, low WC is associated with an increased risk of developing ADL disability in nonagenarian women.

Longitudinal changes in mobility among nonagenarians: the Vitality 90+ Study.

BACKGROUND: Several studies have focused on predictors of mobility limitations and disabilities. Yet little is known about the pace and patterns of mobility changes among very old people. This study examined changes in functional mobility among individuals aged 90 years and older during a 2-9-year follow-up. In addition, we were interested in the patterns of mobility changes. METHODS: Data were collected through a mailed questionnaire in the years 2001, 2003, 2007 and 2010. The study population (n = 948) consisted of individuals from three cohorts (2001, 2003, 2007) who participated in at least two survey rounds and answered the mobility questions. The length of the follow-up varied from 2-9 years between individuals as well as according to how many times an individual took part in the survey. Multilevel ordinal logistic regression analysis was used to evaluate the effects of time, age, gender, cohort and chronic conditions on changes in mobility. RESULTS: At the baseline, "younger" old people, men and individuals in the cohorts for 2003 and 2007 had significantly better mobility compared with women, older individuals and individuals in the 2001 cohort. In addition, individuals with fewer chronic conditions had better mobility than those with more diseases. Mobility declined for most of the participants during the follow-up. The difference in the change in mobility over time for gender, age or chronic conditions was not statistically significant. The analyses were performed with a subgroup of participants aged 90-91 years at the baseline, and results did not differ substantially from the results for the entire study sample. However, the effect of chronic conditions on the change in mobility was statistically significant among participants aged 90-91years. CONCLUSIONS: No differences were observed in the rate of mobility decline over time between age or gender. The effect of chronic conditions on the change in mobility was significant only among individuals aged 90-91 years. The prevention efforts are important and should focus even more, also among the oldest-old, on additional modifiable risk factors such as maintaining muscle strength.

Association of Body Mass Index and Waist Circumference With Physical Functioning: The Vitality 90+ Study.

BACKGROUND: Both obesity and underweight are associated with impaired physical functioning, but related information on the oldest old population is scarce. Our purpose was to examine whether body mass index, waist circumference (WC), and their combination are associated with physical performance and activities of daily living (ADL) disability in 90-year-old women and men. METHODS: Data are from the Vitality 90+ Study, which is a population-based study of persons with age ≥90 years living in the area of Tampere, Finland. Altogether 416 women and 153 men, aged 90-91 years, provided data on body mass index, WC, chair stand, and Barthel Index. Comorbidity, physical exercise, smoking history, living residence, and sample year were used as covariates in multinomial logistic and logistic regression models. RESULTS: Women in the highest WC tertile had lower physical performance and were more likely unable to perform the chair stand than women in the lowest WC tertile. Women in the highest WC tertile were also more likely to have ADL disability, compared to the lowest WC tertile. In women, overweight and obesity were associated with ADL disability, but not when WC was included in the model. Men with body mass index ≥25 kg/m(2) and WC < sex-specific median were less likely to have ADL disability. Similarly classified women were less likely to have low performance or unable to perform chair stand (marginally significant). CONCLUSIONS: High WC in the oldest old women, but not in men, is associated with both poor physical performance and ADL disability.

Predictors of mortality in men and women aged 90 and older: a nine-year follow-up study in the Vitality 90+ study.

BACKGROUND: information about the predictors of mortality among the oldest-old is limited. Also possible gender differences are poorly known. OBJECTIVE: to examine the predictors of mortality among individuals aged 90 and older, focusing on differences between men and women. We also analysed gender differences in survival at different levels of mobility and activities in daily living (ADL). DESIGN: this 9-year follow-up study is part of the Vitality 90+ study, a population-based study of people aged 90 and older. SUBJECTS: all inhabitants aged 90 and older in the area of Tampere, Finland were contacted, irrespective of health or dwelling place. The study population consisted of 171 men and 717 women. METHODS: data were collected with a mailed questionnaire asking questions concerning ADL and mobility, self-rated health, chronic conditions and socio-economic factors. The participation rate was 79%. Cox regression enter models were used for the analysis. RESULTS: older age, male gender, disability in ADL and mobility, poor self-rated health and institutionalisation increased the risk of mortality in the total study group. In age-adjusted Cox regression models, ADL and mobility were stronger predictors in men than in women (gender interactions, P < 0.001). Among those who were partly but not totally dependent in ADL or mobility women survived longer than men. CONCLUSION: the same health indicators that are important at younger old age also predict mortality in the oldest-old. Disability increases the likelihood of death more in men than women. At a very old age, women survive longer with moderate disability than do men.

Inflammation, adiposity, and mortality in the oldest old.

BACKGROUND: Increased proinflammatory status is associated with both increased adiposity and higher mortality risk. Thus, it is paradoxical that mild obesity does not predict increased mortality in older adults. We investigated the association of inflammatory markers with body mass index (BMI), waist circumference (WC), and waist-to-hip ratio (WHR) in nonagenarians, and the combined effects of BMI, WC, WHR, and inflammatory status on mortality. METHODS: This study was based on a prospective population-based study, Vitality 90+, carried out in Tampere, Finland. Altogether, 157 women and 53 men aged 90 years were subjected to anthropometric measurements, blood samples, and a 4-year mortality follow-up. Inflammatory status was based on sex-specific median levels of interleukin-1 receptor antagonist (IL-1RA), interleukin-6 (IL-6), C-reactive protein (CRP), and tumor necrosis factor-α (TNF-α). RESULTS: In the unadjusted linear regression analyses, IL-1RA, CRP, and TNF-α were positively associated with BMI and WC in women, whereas in men IL-1RA was positively associated with BMI and IL-6 positively with WC. In the models adjusted for diseases, functional status, and smoking, IL-1RA and CRP were positively associated with BMI and WC in women. Low WC and WHR combined with low inflammation protected from mortality in women and high BMI and WC regardless of inflammation protected from mortality in men in the adjusted Cox regression analysis. CONCLUSIONS: In the oldest old, the effect of adiposity in combination with inflammatory status on mortality differs between men and women. More research is needed to disentangle the role of adiposity among the oldest old.

Long-term determinants of muscle strength decline: prospective evidence from the 22-year mini-Finland follow-up survey.

OBJECTIVES: To examine long-term changes in handgrip strength and the factors predicting handgrip strength decline. DESIGN: Longitudinal cohort study with 22 years of follow-up. SETTING: Population-based Mini-Finland Health Examination Survey in Finland. PARTICIPANTS: Nine hundred sixty-three men and women aged 30 to 73 at baseline. MEASUREMENTS: Handgrip strength was measured using a handheld dynamometer at baseline and follow-up. Information on potential risk factors, namely lifestyle and chronic conditions, and their changes throughout the follow-up were based on health interviews. RESULTS: Based on linear mixed-effect models, midlife physically strenuous work, excess body weight, smoking, cardiovascular disease, hypertension, diabetes mellitus, and asthma predicted muscle strength decline over 22 years of follow-up (P < .05 for all). In addition, pronounced weight loss, becoming physically sedentary, persistent smoking, incident coronary heart disease, other cardiovascular disease, diabetes mellitus, chronic bronchitis, chronic back syndrome, long-lasting cardiovascular disease, hypertension, and asthma were associated with accelerated handgrip strength decline (P < .05 for all). CONCLUSION: Lifestyle and physical health earlier in life determine rate of muscle strength decline in old age. Efforts should be made to recognize persons at risk in a timely manner and target early interventions to middle-aged persons to slow down muscle strength decline and prevent future functional limitations and disability.

Associations between inflammatory markers, candidate polymorphisms and physical performance in older Danish twins.

Inflammation may play an essential role in the decline of physical performance. In this study we investigated the associations between inflammatory markers, candidate polymorphisms and physical performance in elderly people. Plasma levels of TNF-α, IL-6, CRP, fibrinogen, sICAM-1 and candidate polymorphisms were measured in 600 twin individuals aged 73 years and older participating in the Longitudinal Study of Aging Danish Twins. Physical performance was assessed using a self-reported measure. The inclusion of twins allowed both traditional and within-twin-pair analysis which permitted control for shared environment and genetic factors. Higher levels of inflammatory markers were generally associated with a lower level of physical performance. The TNFα-238G/A polymorphism was significantly associated with physical performance in men, with A allele carriers having significantly better performance than GG homozygotes. However, this gene variation seems to have only a minor role in explaining the associations between the levels of inflammatory markers and physical performance. When using twin pair analysis to test whether genetic factors in general account for this association, results showed that the association between the level of fibrinogen and physical performance could be caused by genetic factors. Also the association between the level of TNF-α and physical performance in males could be caused by genetic factors. However, other gene variations than the candidate gene polymorphisms studied here seem to explain the major part of the genetic proportion of this association.

Vision in relation to lower extremity deficit in older women: cross-sectional and longitudinal study.

BACKGROUND AND AIMS: Vision problems are common experiences within the older population. This study aimed to examine the association between vision and lower extremity impairment. METHODS: 434 women aged 63-75 participated in visual acuity (VA) measurements at baseline and 313 persons at three-year follow-up. Measurements of lower extremity function included maximal isometric knee extension strength, leg extension power, maximal walking speed and standing balance. RESULTS: At baseline, knee extension strength was lower among participants with visual impairment (VI) (273.2±6.4 N) compared to those with good vision (306.5±5.9 N, p<0.001) as well as leg extension power (95.2±2.7 W vs 104.2±2.6 W, p=0.009) and maximal walking speed (1.6±0.02 m/s vs 1.8±0.03 m/s, p<0.001). Higher velocity moment among persons with VI (53.5±2.7 mm²/s vs 42.7±1.4 mm²/s, p<0.001) indicated that persons with VI had poorer balance compared to persons with good vision. Decreased isometric knee extension strength (OR 1.26, 95% CI 1.09-1.45), poorer standing balance (OR 1.16, 95% CI 1.00-1.35) as well as lower maximal walking speed (OR 1.34, 95% CI 1.13-1.59) were associated with VI in the logistic regression models. Additionally, the association between poorer leg extension power and VI (OR 1.14, 95% CI 0.99-1.31) was of borderline statistical significance. In longitudinal analyses, VI did not predict decline in lower extremity function. CONCLUSIONS: Lower extremity impairment was associated with VI among relatively healthy older women. However, change in lower extremity function was quite similar between the vision groups. It is possible that decreased VA may be a marker of underlying systemic factors or the aging process, which lead to poorer functional capacity, or there may be shared background factors, which lead to decreased vision and lower extremity impairment.

Body mass index, waist circumference, and waist-to-hip ratio as predictors of mortality in nonagenarians: the Vitality 90+ Study.

BACKGROUND: The associations of body mass index (BMI) and abdominal obesity with mortality among very old people are poorly known. The purpose of this study was to investigate the association of BMI, waist circumference (WC), and waist-to-hip ratio with mortality in nonagenarians. METHODS: This study is part of a prospective population-based study, Vitality 90+, including both community-dwelling and institutionalized persons from Tampere, Finland. Altogether 192 women and 65 men aged 90 years were subjected to anthropometric measurements, a baseline interview, and a 4-year mortality follow-up. Cox proportional hazards models were used in the statistical analyses. RESULTS: In men, normal weight indicated a three times higher mortality risk (hazard ratio [HR] 3.09, 95% confidence interval [CI] 1.35-7.06) compared with overweight, and WC was inversely associated with mortality (HR 0.96, 95% CI 0.93-1.00) after adjustment for covariates. In women, the univariate waist-to-hip ratio (HR 1.43, 95% CI 1.06-1.92) and BMI-adjusted waist-to-hip ratio (HR 1.45, 95% CI 1.07-1.97) were positively associated with mortality. Also, overweight women whose WC was <86 cm had lower mortality than normal weight women with similar WC (HR 0.34, 95% CI 0.12-0.97). CONCLUSIONS: In nonagenarian men, low BMI and low WC predict increased mortality. In nonagenarian women, waist-to-hip ratio alone and adjusted for BMI is positively associated with mortality. The potential positive effects of overweight combined with WC warrant more detailed analyses in larger data. In all, future studies are needed to better understand the health and functional consequences of body composition among the oldest old.

Inflammatory markers and physical performance among nonagenarians.

BACKGROUND: Recent studies have suggested that inflammation may play an important role in aging and the development of disabilities, but knowledge about its importance in the development of muscle weakness and functional disabilities in very old people is limited. This study examined associations between inflammatory markers and physical performance among nonagenarians. METHODS: The population-based sample consisted of 197 women and 65 men aged 90 years. Physical performance was assessed according to the Barthel Index, the chair stand, and handgrip strength. Plasma levels of interleukin-6 (IL-6), interleukin-1 receptor antagonist (IL-1Ra), and C-reactive protein (CRP) were determined. RESULTS: A gender-adjusted linear regression model showed that high levels of CRP, IL-6, and IL-1Ra were significantly associated with poor handgrip strength (p = .041, p = .023, p < .001, respectively). After adjustment for diseases, smoking and physical exercise high levels of IL-6 and IL-1Ra were still significantly associated with poor hand grip strength (p = .048, p = .004, respectively). In the gender-adjusted model, high levels of CRP, IL-6, and IL-1Ra were significantly associated with a worse Barthel Index (p = .009, p = .004, p = .004, respectively). High levels of CRP and IL-6 were still significantly associated with a worse Barthel Index after adjusted for diseases, smoking and physical exercise (p = .034, p = .041, respectively). In the chair stand, no significant association with inflammatory markers was found. CONCLUSIONS: Associations between high levels of inflammatory markers and worse handgrip strength as well as a worse Barthel Index result were evident among nonagenarians. However, the association with the chair stand was not significant.

Genetic and environmental effects on isometric muscle strength and leg extensor power followed up for three years among older female twins.

The purpose of this study was to examine changes in the contribution of genetic and environmental effects to isometric knee extensor strength and leg extensor power among 63- to 76-year-old female twins over a 3-yr follow-up. At baseline in 2000 the sample comprised 206 monozygotic (MZ) and 228 dizygotic (DZ) twin individuals, and at follow-up in 2003 the sample comprised 149 MZ and 164 DZ twin individuals. Genetic modeling showed that genetic effects explained 58% (95% CI: 46-68%) of the variance in muscle strength at baseline and 56% (95% CI: 41-68%) at follow-up, with no occasion-specific genetic effect. Nonshared environmental effects accounted for 42% (95% CI: 32-54%) of the variation at baseline and 15% (95% CI: 7-26%) at follow-up. In addition, new nonshared environmental effects explained the remaining variance, 29% (95% CI: 22-37%) of muscle strength at follow-up. For muscle power, the same genetic effects accounted for 67% (95% CI: 57-74%) of the variation at baseline and 48% (95% CI: 34-61%) at follow-up. Nonshared environmental effects in common at both measurement points explained 33% (95% CI: 25-43%) of the total variation at baseline and 11% (95% CI: 5-21%) at follow-up. The remaining variance of muscle power at follow-up was accounted for by time-specific environmental effects. Results indicated that the contribution of genetic effects to isometric muscle strength was stable, whereas for leg extensor power the proportion of genetic effects decreased during the follow-up. We observed new specific environmental effects underlying follow-up muscle strength and power, which effects could be due to the onset of new disease processes or changes in lifestyle.

Muscle cross-sectional area and structural bone strength share genetic and environmental effects in older women.

The purpose of this study was to estimate to what extent muscle cross-sectional area of the lower leg (mCSA) and tibial structural strength are influenced by common and trait-specific genetic and environmental factors. pQCT scans were obtained from both members of 102 monozygotic (MZ) and 113 dizygotic (DZ) 63- to 76-yr-old female twin pairs to estimate the mCSA of the lower leg, structural bending strength of the tibial shaft (BSIbend), and compressive strength of the distal tibia (BSIcomp). Quantitative genetic models were used to decompose the phenotypic variances into common and trait-specific additive genetic (A), shared environmental (C), and individual environmental (E) effects. The age-adjusted trivariate independent pathway model showed that the total relative contributions of A, C, and E were, respectively, 75%, 0%, and 25% for mCSA, 55%, 20%, and 25% for BSIbend, and 40%, 37%, and 23% for BSIcomp. In addition, the model showed that all three traits shared genetic and individual environmental factors. BSIbend and BSIcomp had common shared environmental factors and were also influenced by trait-specific genetic factors. In conclusion, the association between muscle cross-sectional area and structural bone strength has its origins in both genetic and environmental effects in older women. These results suggest that in older women the same genetic and environmental factors may predispose to or, conversely, protect from both sarcopenia and bone fragility.

Genetics of maximal walking speed and skeletal muscle characteristics in older women.

The aim of this study was to examine whether maximal walking speed, maximal isometric muscle strength, leg extensor power and lower leg muscle cross-sectional area (CSA) shared a genetic effect in common. In addition, we wanted to identify the chromosomal areas linked to maximal walking speed and these muscle characteristics and also investigate whether maximal walking speed and these three skeletal muscle characteristics are regulated by the same chromosomal areas. We studied 217 monozygotic (MZ) and dizygotic (DZ) female twin pairs aged 66 to 75 years in the Finnish Twin Study on Aging study. The DZ pairs (94) were genotyped for 397 microsatellite markers in 22 autosomes and X-chromosome. Genetic modeling showed that, muscle CSA, strength, power and walking speed shared a genetic effect in common which accounted for 7% of the variation in CSA, 51% in strength, 37% in power and 35% in walking speed. The results of an explorative multipoint linkage analysis suggested that the highest LOD score found for each phenotype was 2.41 for walking speed on chromosome 13q22.1, 2.14 for strength on chromosome 15q14, 2.84 for power on chromosome 8q24.23, and 2.93 for muscle CSA on chromosome 20q13.31. Also a suggestive LOD score, 2.68, for muscle CSA was found on chromosome 9q34.3. The chromosomal areas of a suggestive linkage for strength and power partly overlapped LOD scores higher than 1.0 being seen for these phenotypes on chromosome 15. The present study was the first genome-wide linkage analysis to be conducted for these multifactorial and clinically important phenotypes underlying functional independence in older women.

Catechol-o-methyltransferase gene polymorphism is associated with skeletal muscle properties in older women alone and together with physical activity.

BACKGROUND: Muscle strength declines on average by one percent annually from midlife on. In postmenopausal women this decrement coincides with a rapid decline in estrogen production. The genetics underlying the effects of estrogen on skeletal muscle remains unclear. In the present study, we examined whether polymorphisms within COMT and ESR1 are associated with muscle properties and assessed their interaction and their combined effects with physical activity. METHODOLOGY/PRINCIPAL FINDINGS: A cross-sectional data analysis was conducted with 434 63-76-year-old women from the population-based Finnish Twin Study on Aging. Body anthropometry, muscle cross-sectional area (mCSA), isometric hand grip and knee extension strengths, and leg extension power were measured. COMT Val158Met and ESR1 PvuII genotypes were determined by the RFLP method. mCSA differed by COMT genotypes (p = 0.014) being significantly larger in LL than HL individuals in unadjusted (p = 0.001) and age- and height-adjusted model (p = 0.004). When physical activity and age were entered into GEE model, COMT genotype had a significant main effect (p = 0.038) on mCSA. Furthermore, sedentary individuals with the HH genotype had lower muscle mass, strength and power, but they also appeared to benefit the most from physical activity. No association of ESR1 PvuII polymorphism with any of the muscle outcomes was observed. CONCLUSIONS/SIGNIFICANCE: The present study suggests that the COMT polymorphism, affecting the activity of the enzyme, is associated with muscle mass. Furthermore, sedentary individuals with potential high enzyme activity were the weakest group, but they may potentially benefit the most from physical activity. This observation elucidates the importance of both environmental and genetic factors in muscle properties.