Interpretation of the prostate-specific antigen history in assessing life-threatening prostate cancer

OBJECTIVE

To present an effective approach to the early detection of lethal prostate cancer using longitudinal data on prostate-specific antigen (PSA) and its rate of change, i.e. PSA velocity (PSAV). This longitudinal approach might also be extendible to other biomarkers.

SUBJECTS AND METHODS

PSAV was calculated using five techniques for 634 subjects with at least three PSA measurements in a longitudinal ageing study, censoring PSA levels of > 10 ng/mL. The efficacy for predicting death from prostate cancer was assessed with concordance indices and by using net reclassification improvement (NRI), which indicated the net increase in sensitivity and specificity when adding a biomarker to a base Cox proportional hazards model. The PSAV techniques were compared for the 5-10 years before the clinical diagnosis of prostate cancer. The most effective technique was then applied at the transition point when each man's PSA history curve transformed from linear to exponentially increasing, and its predictive value was compared to that of concurrent PSA level.

RESULTS

A PSA transition point was found in 522 (82%) of the 634 men, including all 11 who died from prostate cancer. At the transition point, the mean PSA level was 1.4 ng/mL, and PSAV but not PSA level was significantly higher among men who died from prostate cancer than among men who did not (P = 0.021 vs P = 0.112; Wilcoxon two-sample test). At the transition point, adding PSAV to a base model consisting of age and date of diagnosis improved the concordance index by 0.05, and significantly improved the overall sensitivity and specificity (NRI, P = 0.028), while adding PSA level to the same base model resulted in little improvement (concordance index increase < 0.01 and NRI P = 0.275).

CONCLUSION

When the shape of a man's PSA history curve changes from linear to exponential, PSAV might help in the early identification of life-threatening prostate cancer at a time when PSA values are still low in most men.

Comprehensive fine mapping of chr12q12-14 and follow-up replication identify activin receptor 1B (ACVR1B) as a muscle strength gene

Muscle strength is important in functional activities of daily living and the prevention of common pathologies. We describe the two-staged fine mapping of a previously identified linkage peak for knee strength on chr12q12-14. First, 209 tagSNPs in/around 74 prioritized genes were genotyped in 500 Caucasian brothers from the Leuven Genes for Muscular Strength study (LGfMS). Combined linkage and family-based association analyses identified activin receptor 1B (ACVR1B) and inhibin β C (INHBC), part of the transforming growth factor β pathway regulating myostatin - a negative regulator of muscle mass - signaling, for follow-up. Second, 33 SNPs, selected in these genes based on their likelihood to functionally affect gene expression/function, were genotyped in an extended sample of 536 LGfMS siblings. Strong associations between ACVR1B genotypes and knee muscle strength (P-values up to 0.00002) were present. Of particular interest was the association with rs2854464, located in a putative miR-24-binding site, as miR-24 was implicated in the inhibition of skeletal muscle differentiation. Rs2854464 AA individuals were ∼2% stronger than G-allele carriers. The strength increasing effect of the A-allele was also observed in an independent replication sample (n=266) selected from the Baltimore Longitudinal Study of Aging and a Flemish Policy Research Centre Sport, Physical Activity and Health study. However, no genotype-related difference in ACVR1B mRNA expression in quadriceps muscle was observed. In conclusion, we applied a two-stage fine mapping approach, and are the first to identify and partially replicate genetic variants in the ACVR1B gene that account for genetic variation in human muscle strength.

Changes in weight at the end of life: characterizing weight loss by time to death in a cohort study of older men

The purpose of this analysis was to characterize the natural history of weight change in the years prior to death among older persons and to examine how this pattern varies according to longevity and cause of death. Weight trajectories were analyzed by using data from 800 male decedents from the Baltimore Longitudinal Study of Aging (Maryland, 1958-2005) observed beginning an average of 19 years before death. A model including 3 distinct periods of weight change (weight stability/gain, mild weight loss, and accelerated weight loss before death) provided the best fit for all age-at-death groups. Approximately 9 years before death, the rate of weight loss increased to an average of 0.39 kg/year (P < 0.001) for all-cause mortality. For cancer deaths, weight loss accelerated significantly 3 years before death, regardless of age group. For cardiovascular deaths, the best-fitting inflection point increased with age, from 5 years for participants aged 60-69 years to 9-10 years before death for those aged 80 years or older. Results suggest that weight loss in older persons may begin earlier than previously believed. The duration of weight loss for noncancer deaths suggests that even distal changes in energy balance may be linked to risk of death.

Validity of clinically derived cumulative somatosensory impairment index

DESIGN

Prospective cohort study.

SETTING

Population-based cohort.

PARTICIPANTS

InCHIANTI ("Invecchiare in Chianti" or aging in the Chianti area) study participants (N=960; age, 21-91 y, 51.8% women).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The Cumulative Somatosensory Impairment Index was derived from baseline performance on clinical tests of pressure sensitivity, vibration sensitivity, proprioception, and graphesthesia. Global postural control was assessed using Frailty and Injuries Cooperative Studies of Intervention Techniques (FICSIT) balance test, time to complete 5 repeated chair stands, and fast walking speed, at baseline and at 3-year follow-up.

RESULTS

In participants without neurologic conditions (n=799), the Cumulative Somatosensory Impairment Index was significantly different in age groups classified by decades (P<.001). Compared with participants without prevalent conditions, the Cumulative Somatosensory Impairment Index was significantly higher in persons with diabetes (P=.017), peripheral arterial disease (P=.006), and a history of stroke (P<.001). In the overall population (N=960), in the fully adjusted multiple regression models, the Cumulative Somatosensory Impairment Index independently predicted deterioration in FICSIT scores (P=.002), time for 5 repeated chair stands (P<.001), and fast gait speed (P=.003) at 3-year follow-up.

CONCLUSIONS

The Cumulative Somatosensory Impairment Index is a valid measure that detects relevant group differences in lower limb somatosensory impairment and is an independent predictor of decline in postural control over 3 years.

Nonsteroidal anti-inflammatory drugs, aspirin, and cognitive function in the Baltimore longitudinal study of aging

OBJECTIVES

To examine the relations between the use of nonaspirin, nonsteroidal anti-inflammatory drugs (NSAIDs) and aspirin and age-related change in multiple domains of cognitive function in community-dwelling individuals without dementia.

DESIGN

Longitudinal, with measures obtained on one to 18 occasions over up to 45 years.

SETTING

General community.

PARTICIPANTS

A volunteer sample of up to 2,300 participants from the Baltimore Longitudinal Study of Aging free of diagnosed dementia.

MEASUREMENTS

At each visit, reported NSAID or aspirin use (yes/no) and tests of verbal and visual memory, attention, perceptuo-motor speed, confrontation naming, executive function, and mental status.

RESULTS

Mixed-effects regression models revealed that NSAID use was associated with less prospective decline on the Blessed Information-Memory-Concentration (I-M-C) Test, a mental status test weighted for memory and concentration (P<.001), and Part B of the Trail Making Test, a test of perceptuo-motor speed and mental flexibility (P<.05). In contrast, aspirin use was related to greater prospective decline on the Blessed I-M-C Test (P<.05) and the Benton Visual Retention Test, a test of visual memory (P<.001).

CONCLUSION

Consistent with studies of incident dementia, NSAID users without dementia displayed less prospective decline in cognitive function, but on only two cognitive measures. In contrast, aspirin use was associated with greater prospective cognitive decline on select measures, potentially reflecting its common use for vascular disease prophylaxis. Effect sizes were small, calling into question clinical significance, although overall public health significance may be meaningful.

Is longitudinal pulse pressure a better predictor of 24-hour urinary albumin excretion than other indices of blood pressure?

The strong relationship between urinary albumin excretion (UAE) and pulse pressure (PP) in cross-sectional studies suggests that pressure pulsatility may contribute to renal microvascular injury. The longitudinal relationships between UAE and the various indices of blood pressure (BP) are not well studied. We compared the associations of UAE with the longitudinal exposure to PP and systolic, diastolic, and mean BPs. UAE was measured from 24-hour urine collections in 450 community-dwelling subjects (age: 57+/-15 years, 53% women, all with UAE <200 microg/min). For each subject, longitudinal indices of BP were estimated by dividing the area under the curve of serial measurements of BP (median: 5) during 1 to 22 years preceding UAE measurement by the number of follow-up years. Median (interquartile range) UAE was 4.7 microg/min (3.3 to 7.8 microg/min) in women and 5.2 microg/min (3.7 to 9.8 microg/min) in men. In women, UAE was not related to longitudinal indices of BP. In men, in multivariable-adjusted models that included either longitudinal systolic and diastolic BPs or longitudinal PP and mean BP, UAE was independently associated with systolic (standardized regression coefficient [beta]=0.227; P=0.03) but not with diastolic (beta=-0.049; P=0.59) BP and with PP (beta=0.216; P=0.01) but not with mean BP (beta=0.032; P=0.72). Comparisons of these 2 models and stepwise regression analyses both indicated that, of the 4 longitudinal indices of BP, PP was the strongest predictor of UAE in men. The pulsatile component of BP confers the highest risk for BP-induced renal microvascular injury. Future studies should examine whether PP reduction provides additional renoprotection beyond that attained by conventional BP goals alone.

Prosodic changes in aphasic speech: timing

Controversy remains about the impairment of prosody in aphasia, particularly with regard to speech timing. This paper addresses this topic through an analysis of timing in four sets of a common morphological paradigm. The paradigm consisted of a basic form (stem) and two longer derived forms (e.g. zip, zipper, zippering). Normally, vowel durations are shorter in longer derived forms (e.g. zippering) than in the stem (e.g. zip), due to a process called 'initial shortening'. Twelve patients with aphasia (four each Broca, Wernicke, and Anomic), and 11 age-matched healthy adults were assessed. Structural (CT) and functional brain imaging (PET) were available for all patients. While all groups showed initial shortening between the stem and the derived forms, the patients with Broca's aphasia presented an inverse pattern between the two derived forms (longer initial vowel in 'zippering' than 'zipper'), and the patients with Wernicke's aphasia produced significantly longer vowel durations overall than the healthy participants. The results are related to radiological information regarding the location of structural and functional brain damage and relative preservation and loss of prosodic features in cerebral damage.

Bone mineral content and prostate cancer risk: data from the Baltimore Longitudinal Study of Aging

STUDY TYPE

Aetiology (inception cohort) Level of Evidence 2b.

OBJECTIVE

To determine whether there might be differences in bone mineral content (BMC) between men who develop life-threatening prostate cancer and those who do not, as bone is a common site of prostate cancer metastases.

SUBJECTS AND METHODS

From 1973 to 1984, BMC was serially measured in 519 participants (778 observations) as part of a longitudinal study of ageing. We examined the association between serial BMC measurements with the development of overall and high-risk prostate cancer over the next one to three decades. For all prostate cancer cases, BMC was censored at the time of diagnosis.

RESULTS

During a median (range) overall follow-up of 21.1 (0.2-35.0) years after the last BMC measurement, 76 (14.6%) men were later diagnosed with prostate cancer (18 high-risk and 58 not high-risk). BMC declined with age to a greater extent in healthy controls than among men diagnosed with prostate cancer (P = 0.018, likelihood ratio test), and tended to decline less in high-risk than non-high-risk cases.

CONCLUSION

The distribution of BMC was significantly different between men who did and did not develop prostate cancer, over an extended follow-up. Specifically, BMC appeared to decline to a greater extent with age among healthy controls than in men with prostate cancer, especially high-risk disease. The biology underlying the lesser decline in BMC among men with prostate cancer remains unclear, but suggests that host factors in the bony milieu might be associated with prostate cancer development and progression.

Intima-media thickness and regional cerebral blood flow in older adults

BACKGROUND AND PURPOSE

The relationship between the thickness of the carotid intima (IMT) and brain function remains unclear in those without clinical manifestations of cerebrovascular disease. Understanding the neural correlates of this vascular measure is important in view of emerging evidence linking poorer cognitive performance with increased IMT in individuals without clinical cerebrovascular disease.

METHODS

Seventy-three participants in the Baltimore Longitudinal Study of Aging (70.9 years; SD, 7.3) were evaluated with carotid artery ultrasound and resting [(15)O]H(2)O positron emission tomography.

RESULTS

After adjusting for age, gender, and gray and white matter volumes in the regions where IMT is related to regional cerebral blood flow (rCBF), we found that higher IMT was associated with lower rCBF in lingual, inferior occipital, and superior temporal regions. Higher IMT was also associated with higher rCBF in medial frontal gyrus, putamen, and hippocampal-uncal regions (P=0.001). Whereas women had lower IMT (P=0.01) and mean arterial pressure (P=0.05) than men, they showed more robust associations between IMT and rCBF. The relationship between IMT and rCBF was only minimally affected by additional adjustment for mean arterial pressure.

CONCLUSIONS

IMT is related to patterns of resting rCBF in older adults without clinical manifestations of cerebrovascular disease, suggesting that there are regional differences in CBF that are associated with subclinical vascular disease.

Should prostate specific antigen be adjusted for body mass index? Data from the Baltimore Longitudinal Study of Aging

PURPOSE

Obesity may be associated with lower prostate specific antigen through hemodilution. We examined the relationship between body mass index and prostate specific antigen by age in men without prostate cancer in a longitudinal aging study to determine whether prostate specific antigen must be adjusted for body mass index.

MATERIALS AND METHODS

The study population included 994 men (4,937 observations) without prostate cancer in the Baltimore Longitudinal Study of Aging. Mixed effects models were used to examine the relationship between prostate specific antigen and body mass index in kg/m(2) by age. Separate models were explored in men with prostate cancer censored at diagnosis, for percent body fat measurements, for weight changes with time and adjusting for initial prostate size in 483 men (2,523 observations) with pelvic magnetic resonance imaging measurements.

RESULTS

In men without prostate cancer body mass index was not significantly associated with prostate specific antigen after adjusting for age (p = 0.06). A 10-point body mass index increase was associated with a prostate specific antigen difference of -0.03 ng/ml (95% CI -0.40-0.49). Results were similar when men with prostate cancer were included, when percent body fat was substituted for body mass index, and after adjusting for prostate volume. Longitudinal weight changes also had no significant association with prostate specific antigen.

CONCLUSIONS

Consistent with prior studies, we found an inverse relationship between obesity and serum prostate specific antigen. However, the magnitude of the difference was small. Thus, adjusting prostate specific antigen for body mass index does not appear warranted.

Candidate gene polymorphisms for ischemic stroke

BACKGROUND AND PURPOSE

Ischemic stroke (IS) is a multifactorial disorder with strong evidence from twin, family, and animal model studies suggesting a genetic influence on risk and prognosis. Several candidate genes for IS have been proposed, but few have been replicated. We investigated the contribution of 67 candidate genes (369 single nucleotide polymorphisms [SNPs]) on the risk of IS in a North American population of European descent.

METHODS

Two independent studies were performed. In the first, 342 SNPs from 52 candidate genes were genotyped in 307 IS cases and 324 control subjects. The SNPs significantly associated with IS were tested for replication in another cohort of 583 IS cases and 270 control subjects. In the second study, 212 SNPs from 62 candidate genes were analyzed in 710 IS cases with subtyping available and 3751 control subjects.

RESULTS

None of the candidate genes (SNPs) were significantly associated with IS risk independent of known stroke risk factors after correction for multiple hypotheses testing.

CONCLUSIONS

These results are consistent with previous meta-analyses that demonstrate an absence of genetic association of variants in plausible candidate genes with IS risk. Our study suggests that the effect of the investigated SNPs may be weak or restricted to specific populations or IS subtypes.

Sequential use of transcriptional profiling, expression quantitative trait mapping, and gene association implicates MMP20 in human kidney aging

Kidneys age at different rates, such that some people show little or no effects of aging whereas others show rapid functional decline. We sequentially used transcriptional profiling and expression quantitative trait loci (eQTL) mapping to narrow down which genes to test for association with kidney aging. We first performed whole-genome transcriptional profiling to find 630 genes that change expression with age in the kidney. Using two methods to detect eQTLs, we found 101 of these age-regulated genes contain expression-associated SNPs. We tested the eQTLs for association with kidney aging, measured by glomerular filtration rate (GFR) using combined data from the Baltimore Longitudinal Study of Aging (BLSA) and the InCHIANTI study. We found a SNP association (rs1711437 in MMP20) with kidney aging (uncorrected p = 3.6×10⁻⁵, empirical p = 0.01) that explains 1%–2% of the variance in GFR among individuals. The results of this sequential analysis may provide the first evidence for a gene association with kidney aging in humans.

Although family studies have shown that genes play a role in longevity, it has proven difficult to identify the specific genetic variants involved. We developed a sequential transcriptional profiling and eQTL mapping approach to find genes associated with aging in the kidney. First, we used genome-wide transcriptional profiling to determine which genes change expression with age in kidney tissue. Next, we used two methods to determine which of these age-regulated genes contain SNPs that associate with expression level. The allele-specific expression method, which compares the mRNA levels of the two alleles within heterozygous individuals, was more sensitive than the total expression method. We tested the eQTLs for association with kidney aging in two populations. One gene that encodes an extracellular matrix protein, MMP20, significantly associated with kidney aging, providing the first gene association with kidney aging. Our approach of combining both expression and genotype data can be applied to any phenotype of interest to increase the power to find genetic associations.

Relationship between higher estradiol levels and 9-year mortality in older women: the Invecchiare in Chianti study

OBJECTIVES

To investigate the relationship between total estradiol (E2) levels and 9-year mortality in older postmenopausal women not taking hormone replacement therapy (HRT).

DESIGN

Population-based study of persons living in the Chianti geographic area (Tuscany, Italy).

SETTING

Community.

PARTICIPANTS

A representative sample of 509 women aged 65 and older with measures of total E2.

MEASUREMENTS

Serum total E2 was measured at the University of Parma using ultrasensitive radioimmunoassay (RIA).

RESULTS

Women who died (n=135) during 9 years of follow up were older; had higher total E2 levels; and were more likely to have evidence of stroke, hypertension, diabetes mellitus, and congestive heart failure at baseline than survivors. Higher E2 levels were associated with a greater likelihood of death (hazard ratio (HR)=1.03, 95% confidence interval (CI)=1.01-1.06), and the relationship was independent of age, waist:hip ratio, C-reactive protein, education, cognitive function, physical activity, caloric intake, smoking, and chronic disease (HR=1.08 pg/mL, 95% CI=1.03-1.13, P=.003). The excessive risk of death associated with higher total E2 was not attenuated after adjustment for total testosterone (HR=1.12, 95% CI=1.02-1.18, P<.001) and after further adjustment for insulin resistance evaluated using the homeostasis model assessment (HR=1.07, 95% CI=1.03-1.17, P<.001). Total E2 was highly predictive of death after more than 5 years (HR=1.42: CI 1.01-1.91, P=.04) and not predictive of death for less than 5 years (P=.78).

CONCLUSION

Higher total E2 concentration predicts mortality in older women not taking HRT.

Serum testosterone is associated with aggressive prostate cancer in older men: results from the Baltimore Longitudinal Study of Aging

STUDY TYPE

Prognosis (inception cohort).

LEVEL OF EVIDENCE

1b.

OBJECTIVE

To evaluate the relationship between testosterone levels and the development of high-risk prostate cancer, by prospectively examining serum androgen concentrations in a well-studied cohort, as the role of testosterone in prostate cancer progression is debated.

PATIENTS AND METHODS

The study comprised 781 men in the Baltimore Longitudinal Study of Aging who had sex steroid measurements before a diagnosis of prostate cancer, or at their last visit for those without cancer (no cancer, 636; cancer, not high risk, 109; cancer, high risk, 36). High-risk cancer was defined as death from prostate cancer, a prostate specific antigen (PSA) level of > or =20 ng/mL at diagnosis, or a Gleason score of > or =8. The hazard ratio (HR) of high-risk disease was determined using a Cox proportional hazards regression model with simple updating, and risk rates were stratified by age and tercile for androgens of interest based on the proportional hazards analyses.

RESULTS

The likelihood of high-risk prostate cancer doubled per unit (0.1) increase in the free testosterone index (FTI) for patients aged >65 years (HR 2.07, 95% confidence interval, CI, 1.01-4.23; P = 0.047); the likelihood for men aged < or =65 years was inversely related to the FTI (HR 0.96, 95% CI 0.35-2.6; P = 0.9). The risk rate per person-years increased from lowest to highest tercile of FTI for the oldest men (age >70 years) but this trend was not apparent among younger men.

CONCLUSION

Higher levels of serum free testosterone are associated with an increased risk of aggressive prostate cancer among older men. These data highlight the importance of prospective trials to insure the safety of testosterone-replacement therapy.

Gait speed under varied challenges and cognitive decline in older persons: a prospective study

OBJECTIVE

to examine whether usual gait speed, fast gait speed or speed while walking with a cognitive or neuromuscular challenge predicts evolving cognitive decline over 3 years.

DESIGN

prospective study.

SETTING

population-based sample of community-dwelling older persons.

PARTICIPANTS

660 older participants (age > or = 65 years).

MEASUREMENTS

usual gait speed, fastest gait speed, gait speed during 'walking-while-talking', depression, comorbidities, education, smoking and demographics were assessed at baseline. Cognition was evaluated at baseline and follow-up. A decline in MMSE score by > or = 3 points was considered as significant cognitive decline (SCD).

RESULTS

adjusting for confounders, only fast speed was associated with cognitive performance at 3-year follow-up. One hundred thirty-five participants had SCD over 3 years. Participants in the lowest quartile of usual speed or walking-while-talking speed were more likely to develop SCD. Conversely, participants in the third and fourth quartiles of fast speed were more likely to develop SCD. J-test showed that the model including fast speed quartiles as a regressor was significantly more predictive of SCD than the models with usual speed or walking-while-talking speed quartiles.

CONCLUSION

measuring fast gait speed in older persons may assist in identifying those at high risk of cognitive decline.

Prostate volume changes over time: results from the Baltimore Longitudinal Study of Aging

PURPOSE

According to a 1944 publication by Swyer benign prostatic hyperplasia develops in some men after age 45 with further prostatic growth whereas in other men prostate size remains stable or decreases with advancing age. Although there is an abundance of literature describing prostatic enlargement in association with benign prostatic hyperplasia, less is known about the phenomenon of prostate atrophy.

MATERIALS AND METHODS

In the Baltimore Longitudinal Study of Aging serial pelvic magnetic resonance imaging was performed in men without prostate cancer beginning in 1993. From this population we retrospectively identified 278 men with 2 or more magnetic resonance imaging determined prostate volume measurements to examine differential growth rates in a cohort of community men over time.

RESULTS

Median age was 58 years and median prostate size was 28 cc at study entry. At a median followup of 4.3 years prostate size increased in 61.9% and remained stable or decreased in 38.1% of men. The median rate of volume change was 0.6 cc per year (range -9.9 to 62.1), corresponding to a median growth rate of 2.5% per year (range -29.2 to 176.4%). During followup 64.6% of men with an initial prostate size less than 40 cc had prostate growth compared to only 50.9% of men with an initial prostate size of 40 cc or greater.

CONCLUSIONS

These results suggest that changes in prostate size are highly variable among aging men. Although benign prostatic hyperplasia is common, a considerable proportion of aging men have a stable or decreasing prostate size. Further research is needed to identify the underlying mechanism for such differences in prostate growth.

Carotid intimal medial thickness predicts cognitive decline among adults without clinical vascular disease

BACKGROUND AND PURPOSE

Though clinical cardiovascular and cerebrovascular diseases are established risk factors for cognitive decline and dementia, less is known about the relations between vascular health and cognition among individuals without these diseases. Carotid intimal medial thickness (IMT), a measure of subclinical vascular disease, is associated with concurrent decrements in cognitive function, but relatively little research has examined longitudinal relations between carotid IMT and prospective cognitive decline.

METHODS

We examined relations of carotid IMT to prospective trajectories of cognitive function among 538 (aged 20 to 93, 39% male, 66% white) participants in the Baltimore Longitudinal Study of Aging (BLSA) free of known cardiovascular, cerebrovascular, and neurological disease. Participants underwent initial carotid ultrasonography and repeat neuropsychological testing on up to 8 occasions over up to 11 years of follow-up. Mixed-effects regression analyses were adjusted for age, gender, race, education, mean arterial pressure, body mass index, total cholesterol, smoking, depressive symptoms, and cardiovascular medication use.

RESULTS

Individuals with greater carotid IMT displayed accelerated decline in performance over time on multiple tests of verbal and nonverbal memory, as well as a test of semantic association fluency and executive function.

CONCLUSIONS

Carotid IMT predicts accelerated cognitive decline, particularly in the domain of memory, among community-dwelling individuals free of vascular and neurological disease.

Age-associated changes in motor unit physiology: observations from the Baltimore Longitudinal Study of Aging

OBJECTIVE

To examine motor unit characteristics (size and firing rate) associated with aging.

DESIGN

Cross-sectional, observational.

SETTING

Community.

PARTICIPANTS

Baltimore Longitudinal Study of Aging participants (N=102), aged 22.2 to 94.1 years, were studied.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Surface-represented motor unit size and firing rate were collected from the vastus medialis during knee extension at 10%, 20%, 30%, and 50% of each subject's maximum isometric voluntary contraction (MVC).

RESULTS

MVC declined with older age (P<.0001). Adjusting for differences in MVC, both firing rate and motor unit size per newton force generated began to increase in the 6th decade of life. Motor unit size increased per newton force to a greater extent than firing rate. Those over the age of 75 years also activated significantly larger motor units per unit force (P=.04). Relative to force generated, the average firing rate began increasing at 57.8+/-3.4 years and between 50.2 and 56.4 years (+/-4y) for motor unit size.

CONCLUSIONS

The size of motor units and firing rates used to achieve a given force changes with age, particularly after middle age. Whether these changes precede, follow, or occur concurrent to age-related modifications in muscle structure and contractile properties or sarcopenia is not known.

Prostate specific antigen testing among the elderly--when to stop?

PURPOSE

Prostate specific antigen testing is common in the elderly despite evidence that older men without aggressive prostate cancer are unlikely to benefit from diagnosis and treatment. We evaluated the relationship between prostate specific antigen and the risk of aggressive prostate cancer developing in men of various ages.

MATERIALS AND METHODS

This longitudinal cohort study consisted of 849 men (122 with and 727 without prostate cancer) with serial prostate specific antigen measurements participating in the Baltimore Longitudinal Study of Aging. The primary outcome measure was the proportion of men by prostate specific antigen and age who died of prostate cancer or in whom aggressive prostate cancer developed (death from prostate cancer, a prostate specific antigen 20 ng/ml or greater, or Gleason score 8 or greater).

RESULTS

No participants between 75 and 80 years old with a prostate specific antigen less than 3.0 ng/ml died of prostate cancer. In contrast, men of all ages with a prostate specific antigen of 3.0 ng/ml or greater had a continually increasing probability of death from prostate cancer (Fisher's exact test p <0.001). The time to death or diagnosis of aggressive prostate cancer after age 75 years was not significantly different between the prostate specific antigen categories of 3 to 3.9 and 4 to 9.9 ng/ml (p = 0.634), whereas the time to death or diagnosis of high risk prostate cancer was significantly longer for the prostate specific antigen category of less than 3 vs 3 ng/ml or greater (p = 0.019).

CONCLUSIONS

Men 75 to 80 years old with a prostate specific antigen less than 3 ng/ml are unlikely to die of or experience aggressive prostate cancer during their remaining life, suggesting that prostate specific antigen testing might be safely discontinued for these men.