Aging, androgens, and the metabolic syndrome in a longitudinal study of aging

BACKGROUND

Based on Adult Treatment Panel III criteria, we previously reported that the prevalence of the metabolic syndrome (MS) increased with aging; was higher if elevated 2-h plasma postglucose challenge values were included as a criterion; and was greater in men, compared with women. The aim of this study was to evaluate the relationship between the MS and circulating androgen levels in a cohort of men in the Baltimore Longitudinal Study of Aging.

METHODS AND RESULTS

Study participants were Caucasian community-dwelling adult men in the Baltimore Longitudinal Study of Aging, who underwent a fasting 2-h oral glucose tolerance test and had serum concentrations of total testosterone (T), dehydroepiandrosterone sulfate, and SHBG levels measured. The prevalence of the MS was 4, 21, 21, and 18% for men between the ages of 20 and 39, 40 and 59, 60 and 79, and 80 and 94 yr, respectively. Total T and SHBG were inversely related to the development of the MS over a mean follow-up period of 5.8 yr (range 1.5-14.0 yr), whereas the free T index and body mass index were positively related to the incidence of the MS. Age alone did not predict the development of the MS, nor did the inclusion of abnormal 2-h plasma postglucose challenge levels in the classification of the MS. Stepwise proportional hazards regression analyses showed that among the various measurements, SHBG levels exerted the greatest influence on development of the MS.

CONCLUSION

The prevalence of the MS increased with aging, and this was associated with lower androgen levels. Lower total T and SHBG predicted a higher incidence of the MS.

Changes in leisure time physical activity and risk of all-cause mortality in men and women: the Baltimore Longitudinal Study of Aging

BACKGROUND

Higher levels of leisure time physical activity (LTPA) are associated with reduced mortality. However it is unclear how changes in LTPA over time impact all-cause mortality in men and women.

METHODS

From 1958 to 1996 for men (n=1316) and 1978 to 1996 for women (n=776), participants aged 19-90+ years from the Baltimore Longitudinal Study of Aging (Baltimore, MD) were assessed for LTPA at baseline and at approximately 2-year intervals over a mean follow-up of 21.2+/-9.4 years for men and 10.2+/-5.6 years for women. Death occurred in 538 men and 90 women. LTPA was derived from self-reports of time spent in 97 activities converted into MET-min per 24 h and was further grouped into high-, moderate- and low-intensity LTPA. The longitudinal data was analyzed using mixed effects models to determine the rate of change in LTPA at each assessment. Proportional hazard models were used to assess the associations between LTPA at baseline and rate of change in LTPA with all-cause mortality.

RESULTS

In younger (<70 years) men, those who reported increases or negligible declines in total and high-intensity LTPA had lower all-cause mortality compared to those with greater declines in LTPA. In older (>or=70 years) men, the association between rate of change in high-intensity LTPA and mortality was similar to that seen in younger men. For women, longitudinal analyses showed neither rates of change in total, high-, moderate- nor low-intensity LTPA were predictive of mortality.

CONCLUSIONS

In this health-conscious population, greater longitudinal declines in total and high-intensity LTPA are independent predictors of all-cause mortality in men.

White blood cell count and mortality in the Baltimore Longitudinal Study of Aging

OBJECTIVES

We investigated the secular trend in white blood cell (WBC) count and the relationship between WBC count and mortality between 1958 and 2002.

BACKGROUND

The WBC count is a clinical marker of inflammation and a strong predictor of mortality. Limited data exist on the WBC count secular trend and the relationship between WBC and mortality.

METHODS

One thousand eighty-three women and 1,720 men were evaluated longitudinally in the Baltimore Longitudinal Study of Aging. Blood samples and medical information were collected at the study entry and every 2 years during follow-up visits. The WBC count and all-cause, cardiovascular, and cancer mortality were assessed.

RESULTS

A downward trend in WBC count was observed from 1958 to 2002. The secular downward trend was independent of age, gender, race, smoking, body mass index, and physical activity. The WBC count was nonlinearly associated with all-cause mortality and almost linearly associated with cardiovascular mortality. Participants with baseline WBC <3,500 cells/mm3 and WBC >6,000 cells/mm3 had higher mortality than those with 3,500 to 6,000 WBC/mm3. Within each WBC group, age-adjusted mortality rates declined in successive cohorts from the 1960s to the 1990s. Participants who died had higher WBC than those who survived, and the difference was statistically significant within 5 years before death.

CONCLUSIONS

Our study provides evidence for a secular downward trend in WBC count over the period from 1958 to 2002. Higher WBC counts are associated with higher mortality in successive cohorts. We found no evidence that the decline of age-specific mortality rates that occurred from 1960 to 2000 was attributable to a secular downward trend in WBC.

Activin-type II receptor B (ACVR2B) and follistatin haplotype associations with muscle mass and strength in humans

Genetic variation in myostatin, a negative regulator of skeletal muscle, in cattle has shown remarkable influence on skeletal muscle, resulting in a double-muscled phenotype in certain breeds; however, DNA sequence variation within this gene in humans has not been consistently associated with skeletal muscle mass or strength. Follistatin and activin-type II receptor B (ACVR2B) are two myostatin-related genes involved in the regulation and signaling of myostatin. We sought to identify associations between genetic variation and haplotype structure in both follistatin and ACVR2B with skeletal muscle-related phenotypes. Three hundred fifteen men and 278 women aged 19-90 yr from the Baltimore Longitudinal Study of Aging were genotyped to determine respective haplotype groupings (Hap Groups) based on HapMap data. Whole body soft tissue composition was measured by dual-energy X-ray absorptiometry. Quadriceps peak torque (strength) was measured using an isokinetic dynamometer. Women carriers of ACVR2B Hap Group 1 exhibited significantly less quadriceps muscle strength (shortening phase) than women homozygous for Hap Group 2 (109.2+/-1.9 vs. 118.6+/-4.1 N.m, 30 degrees/s, respectively, P=0.036). No significant association was observed in men. Male carriers of follistatin Hap Group 3 exhibited significantly less total leg fat-free mass than noncarriers (16.6+/-0.3 vs. 17.5+/-0.2 kg, respectively, P=0.012). No significant associations between these haplotype groups were observed in women. These results indicate that haplotype structure at the ACVR2B and follistatin loci may contribute to interindividual variation in skeletal muscle mass and strength, although these data indicate sex-specific relationships.

Association between hormones and metabolic syndrome in older Italian men

OBJECTIVES

To determine whether low levels of testosterone, sex hormone binding globulin (SHBG), insulin-like growth factor-1 (IGF-1), and dehydroepiandrosterone sulfate (DHEAS) and high levels of cortisol and leptin would be associated with metabolic syndrome (MS).

DESIGN

Cross-sectional.

SETTING

Population-based sample of older Italian men.

PARTICIPANTS

Four hundred fifty-two men aged 65 and older enrolled in the Invecchiare in Chianti (InCHIANTI) study.

MEASUREMENTS

Complete data on testosterone, cortisol, DHEAS, SHBG, fasting insulin, IGF-1 and leptin. MS was defined according to Adult Treatment Panel III criteria.

RESULTS

MS was present in 73 men (15.8% of the sample). After adjusting for confounders, total testosterone (P < .05) and log (SHBG) (P < .001) were inversely associated, whereas log (leptin) was positively associated with MS (P < .001). Independent of age, log (SHBG) was positively associated with high-density lipoprotein cholesterol (P < .05) and negatively associated with abdominal obesity (P < .001) and triglycerides (P < .001). Log (leptin) was significantly associated with each component of MS. Cortisol, DHEAS, free and bioavailable testosterone, and IGF-1 were not associated with MS. Having three or more hormones in the lower (for hormones lower in MS) or the upper (for hormones higher in MS) quartile was associated with three times the risk of being affected by MS (odds ratio = 2.8, 95% confidence interval = 1.3-6.9) (P = .005), compared with not having this condition.

CONCLUSION

Total testosterone and SHBG are negatively and leptin is positively associated with MS in older men. Whether specific patterns of hormonal dysregulation predict the development of MS should be tested in longitudinal studies.

Age associated differences in postural equilibrium control: a comparison between EQscore and minimum time to contact (TTC(min))

Increased postural instability and the subsequent elevation in fall incidence with increasing age are important contributors for hip fractures and developing frailty. When testing for such instability, most studies characterize balance in terms of center-of-mass (COM) deviation from a finite point, the "equilibrium point", located at the center of a subject's stance. For example, the clinically accepted equilibrium score (EQscore) represents instability as the maximum peak-to-peak sway about the "equilibrium point". An alternative theory views balance as being controlled within a "stability margin" in which all corrective actions are based on the time to contact (TTC) of the body's COM with that margin. This study examines the differences offered by evaluating balance control using the EQscore and TTC approach across several age groups and sessions. Consenting subjects from the Baltimore Longitudinal Study of Aging were recruited (N=155) from each age decade (20s-80s) who were generally healthy and free from neurological diagnoses. Results showed TTC tests detected significant variations in eyes open versus eyes closed testing that were unpredictable by EQscore. Further, TTC produced differences in age-related stability threats not seen using EQscore. The TTC data also provided a discriminating difference between subjects who fell in the difficult tests and those who maintained posture. Overall, these data suggest EQscore might not sufficiently account for dynamic control components the body may be using to maintain balance. TTC may offer a more accurate estimate of postural stability (functional ability) than EQscore based on its inclusion of a velocity component to detect dynamic changes.

Association of hormonal dysregulation with metabolic syndrome in older women: data from the InCHIANTI study

Metabolic syndrome (MetS) is a strong risk factor for type 2 diabetes and cardiovascular disease. Conditions associated with hyperandrogenism are often associated with glucose intolerance and other features of MetS in young women. As the prevalence of MetS increases with age and is probably multifactorial, it is reasonable to hypothesize that age-related changes in androgens and other hormones might contribute to the development of MetS in older persons. However, this hypothesis has never been tested in older women. We hypothesized that high levels of testosterone, dehydroepiandrosterone sulfate (DHEA-S), and cortisol and low levels of sex hormone-binding globulin (SHBG) and IGF-I would be associated with MetS in a representative cohort of older Italian women independently of confounders (including inflammatory markers). After exclusion of participants on hormone replacement therapy and those with a history of bilateral oophorectomy, 512 women (>/=65 yr) had complete data on testosterone, cortisol, DHEA-S, SHBG, fasting insulin, total and free IGF-I, IL-6, and C-reactive protein (CRP). MetS was defined according to ATP-III criteria. Insulin resistance was calculated according to HOMA. MetS was found in 145 women (28.3%). Participants with vs. those without MetS had higher age-adjusted levels of bioavailable testosterone (P < 0.001), IL-6 (P < 0.001), CRP (P < 0.001), and HOMA (P < 0.001) and lower levels of SHBG (P < 0.001). After adjustment for potential confounders, participants with decreased SHBG had an increased risk of MetS (P < 0.0001) vs. those with low SHBG. In a further model including all hormones and confounders, log SHBG was the only independent factor associated with MetS (OR: 0.44, 95% CI 0.21-0.91, P = 0.027). In older women, SHBG is negatively associated with MetS independently of confounders, including inflammatory markers and insulin resistance. Further studies are needed to support the notion that raising SHBG is a potential therapeutic target for prevention and treatment of MetS.

Sarcopenic obesity and inflammation in the InCHIANTI study

The aging process is often paralleled by decreases in muscle and increases in fat mass. At the extreme these two processes lead to a condition known as "sarcopenic obesity" (Roubenoff R. Ann NY Acad Sci 904: 553-557, 2000). Research suggests that inflammatory cytokines produced by adipose tissue, especially visceral fat, accelerate muscle catabolism and thus contribute to the vicious cycle that initiates and sustains sarcopenic obesity. We tested the hypothesis that obesity and poor muscle strength, hallmarks of sarcopenic obesity, are associated with high circulating levels of proinflammatory cytokines in a random sample of the residents of two municipalities in the Chianti geographic area (Tuscany, Italy). The study sample consisted of 378 men and 493 women 65 yr and older with complete data on anthropometrics, handgrip strength, and inflammatory markers. Participants were cross-classified according to sex-specific tertiles of waist circumference and grip strength and according to a cut point for obesity of body mass index > or =30 kg/m(2). After adjusting for age, sex, education, smoking history, physical activity, and history of comorbid diseases, components of sarcopenic obesity were associated with elevated levels of IL-6, C-reactive protein, IL-1 receptor antagonist, and soluble IL-6 receptor (P < 0.05). Our findings suggest that global obesity and, to a greater extent, central obesity directly affect inflammation, which in turn negatively affects muscle strength, contributing to the development and progression of sarcopenic obesity. These results suggest that proinflammatory cytokines may be critical in both the development and progression of sarcopenic obesity.

Inflammatory factors in age-related muscle wasting

PURPOSE OF REVIEW

This review focuses on recent evidence pointing to the importance of inflammatory factors in the onset and progression of age-related muscle wasting, also known as sarcopenia, and discusses critical areas of uncertainty within the literature that require further development in order to identify novel therapeutics.

RECENT FINDINGS

The research performed in recent years has only strengthened the evidence that inflammatory factors are important in the progression of a catabolic state in muscle wasting. Interactions among various inflammatory cytokines and anabolic factors have been observed, with the balance skewed in favor of catabolism in sarcopenia. Adiposity appears to play an important role in the inflammatory process and possibly the onset of sarcopenia. Inflammatory factors are likely to play an important role in the increased activity of the ubiquitin proteasome, which we argue should be a primary target for the development of molecular therapeutics.

SUMMARY

Future research will need to delve into the molecular interactions that link inflammatory factors and the imbalance between muscle anabolism and catabolism that develops with aging. Identification of specific pathways of importance to sarcopenia will have relevance to a wide range of wasting disorders.

Suppressed anger is associated with increased carotid arterial stiffness in older adults

BACKGROUND

Anger and hostility have been implicated in the pathogenesis of heart disease, but the extent to which the large conduit arteries play an intermediate role in this relationship remains to be clarified. The present study investigated associations of anger frequency and expression style with carotid artery intima-media thickness (IMT) and stiffness in healthy adults older than 50 years.

METHODS

Two hundred participants (95 men) in the Baltimore Longitudinal Study of Aging completed the Spielberger Anger Expression Inventory, which assesses anger frequency (trait anger), anger expression (anger-out), and anger suppression (anger-in). The carotid artery IMT was assessed by ultrasonography. Carotid stiffness was determined from the log of systolic over diastolic blood pressure (BP) as a function of carotid distensibility.

RESULTS

In univariate correlational analysis, a significant positive association of anger-in with stiffness was observed (P < .01), together with a less significant association of anger-in with carotid artery IMT (P < .05). Neither anger-out nor trait anger was significantly associated with carotid artery IMT or stiffness. Moreover, none of the anger measures was significantly associated with resting BP in this normotensive sample. As expected, carotid artery IMT, stiffness, and systolic BP were all positively associated. In multivariate analysis, anger-in remained a determinant of stiffness independent of BP, and a marginally significant determinant of carotid artery IMT.

CONCLUSIONS

This is the first known finding that high anger-in is a significant independent determinant of carotid artery stiffness. These results suggest that high anger-in can potentiate the effects of age on stiffening of the central arteries.

Detection of life-threatening prostate cancer with prostate-specific antigen velocity during a window of curability

BACKGROUND

Prostate-specific antigen (PSA) level is typically used as a dichotomous test for prostate cancer, resulting in overdiagnosis for a substantial number of men. The rate at which serum PSA levels change (PSA velocity) may be an important indicator of the presence of life-threatening disease.

METHODS

PSA velocity was determined in 980 men (856 without prostate cancer, 104 with prostate cancer who were alive or died of another cause, and 20 who died of prostate cancer) who were participants in the Baltimore Longitudinal Study of Aging for up to 39 years. The relative risks (RRs) of prostate cancer death and prostate cancer-specific survival stratified by PSA velocity were evaluated in the three groups of men by Cox regression and Kaplan-Meier analyses. Statistical tests were two-sided.

RESULTS

PSA velocity measured 10-15 years before diagnosis (when most men had PSA levels below 4.0 ng/mL) was associated with cancer-specific survival 25 years later; survival was 92% (95% confidence interval [CI] = 84% to 96%) among men with PSA velocity of 0.35 ng/mL per year or less and 54% (95% CI = 15% to 82%) among men with PSA velocity above 0.35 ng/mL per year (P<.001). Furthermore, men with PSA velocity above 0.35 ng/mL per year had a higher relative risk of prostate cancer death than men with PSA velocity of 0.35 ng/mL per year or less (RR = 4.7, 95% CI = 1.3 to 16.5; P = .02); the rates per 100,000 person-years were 1240 for men with a PSA velocity above 0.35 ng/mL per year and 140 for men with a PSA velocity of 0.35 ng/mL per year or less.

CONCLUSIONS

PSA velocity may help identify men with life-threatening prostate cancer during a period when their PSA levels are associated with the presence of curable disease.

Metabolic factors associated with benign prostatic hyperplasia

CONTEXT

Benign prostatic hyperplasia poses a significant public health problem, but its etiology remains unclear. Obesity and associated abnormalities in glucose homeostasis may play a role in benign prostatic hyperplasia development by influencing prostate growth.

OBJECTIVE

The objective of this study was to determine whether obesity, fasting plasma glucose concentration, and diabetes are associated with radiologically determined prostate enlargement, an objective measure of benign prostatic hyperplasia.

DESIGN

This study was a cross-sectional analysis with robust variance estimates to account for multiple measures over time in the same individuals.

SETTING

This prospective cohort study was composed of community volunteers.

PATIENTS

Patients studied were 422 adult men enrolled in The Baltimore Longitudinal Study of Aging.

MAIN OUTCOME MEASUREMENTS

Total prostate volume as determined by pelvic magnetic resonance imaging was measured.

RESULTS

Among 422 participants, 91 (21.6%) had prostate enlargement (defined as total prostate volume >/= 40 cc) at first visit. Compared with men of normal weight [body mass index (BMI) < 25 kg/m(2)], the age-adjusted odds ratio (OR) for prostate enlargement for overweight men (BMI, 25-29.9 kg/m(2)) was 1.41 (95% CI, 0.84-2.37), for obese men (BMI, 30-34 kg/m(2)) was 1.27 (95% CI, 0.68-2.39), and for severely obese men (BMI >/= 35 kg/m(2)) was 3.52 (95% CI, 1.45-8.56) (P = 0.01). Men with elevated fasting glucose (>110 mg/dl) were more likely to have an enlarged prostate than men with normal fasting glucose (

CONCLUSIONS

Obesity, elevated fasting plasma glucose, and diabetes are risk factors for benign prostatic hyperplasia.

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Key Words Collapse

MESH Headings

• Adult
• Aged
• Aged, 80 and over
• Black People
• Blood Glucose/analysis
• Body Mass Index
• Cohort Studies
• Cross-Sectional Studies
• Diabetes Complications
• Ethnicity
• Humans
• Longitudinal Studies
• Male
• Middle Aged
• Obesity/complications
• Odds Ratio
• Prospective Studies
• Prostate/pathology
• Prostatic Hyperplasia/etiology
• Prostatic Hyperplasia/metabolism
• Prostatic Hyperplasia/pathology
• Testosterone/blood
• Urologic Diseases/etiology
• Waist-Hip Ratio
• White People

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Grants

• Z01 AG000015-49 Intramural NIH HHS

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Circulating inflammatory cytokine expression in men with prostate cancer undergoing androgen deprivation therapy

Prostate cancer (PCa) is one of the most common cancers in men. Androgen deprivation therapy (ADT) is employed in the treatment of patients with metastatic or recurrent PCa, resulting in castrate levels of testosterone. Recent studies have shown that male hypogonadism is associated with increased levels of proinflammatory and diminished concentrations of anti-inflammatory cytokines, which normalize upon testosterone treatment. Furthermore, an inflammatory state is associated with osteoporosis, sarcopenia and metabolic abnormalities. We examined 3 groups of men: 1) 20 men with PCa undergoing ADT for at least 12 months prior to the onset of the study (ADT group); 2) 18 age-matched men with non-metastatic PCa who had undergone local surgery and/or radiotherapy and had not yet received ADT and were eugonadal (non-ADT group); and 3) 20 age-matched healthy eugonadal men (control group). None of the subjects were suffering from any acute or chronic inflammatory conditions. Mean age was similar in the 3 groups (P = .41). Men in the ADT and non-ADT groups had higher BMI compared to the control group (P = .0005 and P = .01, respectively). Men in the ADT group had significantly lower mean serum total (P < .0001) and free (P < .0001) testosterone and estradiol (P < .0001) levels compared to the other 2 groups. No significant differences in serum levels of pro-inflammatory or anti-inflammatory cytokines were observed between the 3 groups. These data suggest that men with PCa undergoing long-term ADT do not have elevated levels of pro-inflammatory cytokines compared to age and disease matched controls. Prospective studies are needed to evaluate for any acute changes in these inflammatory markers that might occur after the initiation of ADT.

Relationship between androgenic hormones and arterial stiffness, based on longitudinal hormone measurements

Circulating testosterone levels (T) decrease with age in men. Low T has been associated with coronary disease and with risk factors for atherosclerosis. This study examines the relationship in men between androgenic hormones and arterial stiffness, a major risk factor for cardiovascular events. T, sex hormone-binding globulin (SHBG), and dehydroepiandrosterone sulfate (DHEAS) were measured longitudinally over 33 yr (follow-up 11.8 +/- 8.3 yr) in 901 men from the Baltimore Longitudinal Study of Aging, of whom 206 (68.1 +/- 13.7 yr) underwent carotid duplex ultrasonography. The 901 men were used to characterize age-associated hormone levels by means of mixed-effects models. Hormone values were estimated for the 206 men at the time of ultrasonography. Free T index (FTI) was calculated by dividing T by SHBG. The arterial stiffness index was calculated from peak systolic and end diastolic diameters of the common carotid artery and simultaneous brachial artery blood pressure. T, FTI, and DHEAS were correlated negatively with age, pulse pressure (PP), and stiffness index (each P < 0.01), whereas SHBG was correlated positively with age and stiffness index (P < 0.01). However, T was the only hormone that predicted the stiffness index after adjustment for age, PP, fasting plasma glucose, body mass index, and total cholesterol. T values 5-10 yr before the carotid study also predicted the stiffness index (P < 0.05). Thus the adverse influence of low T on the cardiovascular system in men may be mediated in part via the effects of T on vascular structure and function.

Age and sex affect human muscle fibre adaptations to heavy-resistance strength training

This study assessed age and sex effects on muscle fibre adaptations to heavy-resistance strength training (ST). Twenty-two young men and women (20-30 years old) and 18 older men and women (65-75 years old) completed 9 weeks of heavy-resistance knee extension exercises with the dominant leg 3 days week(-1); the non-dominant leg served as a within-subject, untrained control. Bilateral vastus lateralis muscle biopsies were obtained before and after ST for analysis of type I, IIa and IIx muscle fibre cross-sectional area (CSA) and fibre type distribution. One-repetition maximum (1-RM) strength was also assessed before and after ST. ST resulted in increased CSA of type I, IIa and IIx muscle fibres in the trained leg of young men, type I and IIa fibres in young women, type IIa fibres in older men, and type IIx fibres in older women (all P<0.05). Analysis of fibre type distribution revealed a significant increase in the percentage of type I fibres (P<0.05) along with a decrease in type IIx fibres (P=0.054) after ST only in young women. There were no significant changes in muscle fibre CSA or fibre type distribution in the untrained leg for any group. All groups displayed significant increases in 1-RM (27-39%; all P<0.01). In summary, ST led to significant increases in 1-RM and type II fibre CSA in all groups; however, age and sex influence specific muscle fibre subtype responses to ST.

Serum testosterone and the risk of prostate cancer: potential implications for testosterone therapy

OBJECTIVE

A potential risk of testosterone replacement therapy is an increase in the incidence of prostate cancer, but it is unclear whether higher levels of serum testosterone are associated with a higher risk of prostate cancer. We prospectively evaluated serum androgen concentrations and prostate cancer risk.

METHOD

Included were 794 members of the Baltimore Longitudinal Study of Aging. We estimated the rate ratio (RR) of prostate cancer by entering serial measures of serum total testosterone, dehydroepiandrosterone sulfate, sex hormone binding globulin, calculated free testosterone, and free testosterone index (FTI) into a Cox proportional hazards regression model with simple updating.

RESULTS

Higher calculated free testosterone was associated with an increased age-adjusted risk of prostate cancer {RRs by quartile: 1.00, 1.52 [95% confidence interval (95% CI), 0.93-2.50], 1.16 (95% CI, 0.61-2.20), 2.59 (95% CI, 1.28-5.25); P(trend) = 0.03}, which persisted after excluding measures in men <45 years of age [RRs by quartile: 1.00, 1.33 (95% CI, 0.78-2.25), 1.26 (95% CI, 0.68-2.33), 1.89 (95% CI, 0.99-3.61); P(trend) = 0.03]. Compared to men with eugonadal FTI (> or = 0.153), men with hypogonadal FTI had a decreased risk of prostate cancer (RR, 0.51; 95% CI, 0.31-0.82).

CONCLUSION

Higher levels of calculated serum free testosterone are associated with an increased risk of prostate cancer. These findings suggest that men receiving testosterone therapy should be regularly monitored for prostate cancer and underscore the need for prospective trials of testosterone therapy incorporating incidence of prostate cancer as a primary safety end point.

The relationship between ciliary neurotrophic factor (CNTF) genotype and motor unit physiology: preliminary studies

Background

Ciliary neurotrophic factor (CNTF) is important for neuronal and muscle development, and genetic variation in the CNTF gene has been associated with muscle strength. The effect of CNTF on nerve development suggests that CNTF genotype may be associated with force production via its influence on motor unit size and firing patterns. The purpose of this study is to examine whether CNTF genotype differentially affects motor unit activation in the vastus medialis with increasing isometric force during knee extension.

Results

Sixty-nine healthy subjects were genotyped for the presence of the G and A (null) alleles in the CNTF gene (n = 57 G/G, 12 G/A). They were tested using a dynamometer during submaximal isometric knee extension contractions that were from 10–50% of their maximal strength. During the contractions, the vastus medialis was studied using surface and intramuscular electromyography with spiked triggered averaging to assess surface-detected motor unit potential (SMUP) area and mean firing rates (mFR) from identified motor units. CNTF genotyping was performed using standard PCR techniques from DNA obtained from leucocytes of whole blood samples. The CNTF G/A genotype was associated with smaller SMUP area motor units and lower mFR at higher force levels, and fewer but larger units at lower force levels than G/G homozygotes. The two groups used motor units with different size and activation characteristics with increasing force generation. While G/G subjects tended to utilize larger motor units with increasing force, G/A subjects showed relatively less increase in size by using relatively larger units at lower force levels. At higher force levels, G/A subjects were able to generate more force per motor unit size suggesting more efficient motor unit function with increasing muscle force.

Conclusion

Differential motor unit responses were observed between CNTF genotypes at force levels utilized in daily activities.

Evaluation of movement speed and reaction time as predictors of all-cause mortality in men

Muscle power is associated with mortality independent of strength, suggesting that movement speed and coordination convey health-related information. We hypothesized that movement speed is a marker of longevity. Our participants included 1196 men who performed a tapping and/or auditory simple (respond to a sound) and disjunctive (respond to a higher pitched sound) reaction-time tasks while participating in the Baltimore Longitudinal Study of Aging. Mortality was assessed over 40 years. Tapping time was associated with mortality (relative risk [RR] = 1.34 per minute, 95% confidence interval [CI], 1.05-1.70) adjusted for age, and persisted with adjustments for arm strength and power. Simple (RR = 1.17 per 100 ms, 95% CI, 1.03-1.32) and disjunctive (RR = 1.14 per 100 ms, 95% CI, 1.03-1.27) reaction times but not their difference (RR = 1.04 per 100 ms, 95% CI, 0.92-1.19) were associated with mortality after adjustments for age, neurological/psychiatric and neck/arm pain histories. Age-associated impairments in motor control systems but not the decision to move affects longevity.