Association between Sedentary Time and Cardiovascular Risk Factors in Korean Adults.

BACKGROUND: Sedentary behavior has been shown to have deleterious effects on cardiovascular outcomes. This study aimed to examine the association between sedentary time and cardiovascular risk factors in Korean adults. METHODS: A cross-sectional study was performed using data from adults aged 19 years and above in the 2013 Korean National Health and Nutrition Examination Survey. Sedentary time was self-reported and categorized into quintiles. Cardiovascular risk factors, including blood pressure (BP), total cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides, low-density lipoprotein cholesterol, and fasting glucose levels, were categorized into dichotomous variables according to the Adult Treatment Panel III criteria. Multivariate logistic regression was performed with adjustment for various demographic and lifestyle variables, body mass index (BMI), waist circumference (WC), and moderate-to-vigorous physical activity. Complex sampling design was used, and survey weights and sample design variables were applied in analyses. RESULTS: A total of 3,301 individuals were included in the analyses, and mean sedentary time was 6.1 h/d. Prolonged sedentary time was significantly associated with high diastolic BP (top vs. bottom quintile: adjusted odds ratio [OR], 1.71; 95% confidence interval [CI], 1.09-2.68; Ptrend=0.03) and low HDL cholesterol level (top vs. bottom quintile: adjusted OR, 1.42; 95% CI, 1.02-1.98; Ptrend=0.02) after adjustment for BMI, WC, moderate-to-vigorous physical activity, and other variables. No significant associations were found between sedentary time and other cardiovascular risk factors. CONCLUSION: Prolonged sedentary time was significantly associated with high diastolic BP and low HDL cholesterol level in Korean adults. The associations were independent of general and abdominal obesity and moderate-to-vigorous physical activities.

Silicon Diphosphide: A Si-Based Three-Dimensional Crystalline Framework as a High-Performance Li-Ion Battery Anode.

The development of an electrode material for rechargeable Li-ion batteries (LIBs) and the understanding of its reaction mechanism play key roles in enhancing the electrochemical characteristics of LIBs for use in various portable electronics and electric vehicles. Here, we report a three-dimensional (3D) crystalline-framework-structured silicon diphosphide (SiP2) and its interesting electrochemical behaviors for superior LIBs. During Li insertion in the SiP2, a three-step electrochemical reaction mechanism, sequentially comprised of a topotactic transition (0.55-2 V), an amorphization (0.25-2 V), and a conversion (0-2 V), was thoroughly analyzed. On the basis of the three-step electrochemical reaction mechanism, excellent electrochemical properties, such as high initial capacities, high initial Coulombic efficiencies, stable cycle behaviors, and fast-rate capabilities, were attained from the preparation of a nanostructured SiP2/C composite. This 3D crystalline-framework-structured SiP2 compound will be a promising alternative anode material in the realization and mass production of excellent, rechargeable LIBs.

Design and baseline characteristics of participants in the Enhancing Physical Activity and Reducing Obesity through Smartcare and Financial Incentives (EPAROSFI): A pilot randomized controlled trial.

BACKGROUND: An activity tracker combined with a smartphone application (smartcare) may help people track and receive feedback on their own activities. However, activity trackers themselves generally fail to drive long-term sustained engagement for a majority of users. One potential strategy for increasing the effectiveness of smartcare is through the use of incentives. The purpose of this pilot randomized trial is to test the feasibility of our intervention and to assess the extent to which smartcare with or without financial incentives can increase physical activity levels and reduce weight over a 12-week period. METHODS/DESIGN: This study employs a three-arm, open-label randomized controlled trial design: control (standard basic education), smartcare, and smartcare plus financial incentives. Male university students with body mass index ≥ 27 are enrolled. Our primary and secondary endpoints are the amount of weight loss and the level of physical activity respectively. The weight loss goal is 3% of baseline at week 4, 5% at week 8, and 7% at week 12. The daily physical activity goal was individualized according to the participants' weight. Process incentives are accumulated when participants met daily physical activity goals, and outcome incentives are provided when they met weight reduction goals. DISCUSSION: Given the global increase in physical inactivity and obesity, there is a growing need for effective, scalable, and affordable health promotion strategies. Our proof-of-concept study will provide the evidence for the combination of rising health promotion technology of activity trackers and smartphone applications with the modern concept of behavioral economics using financial incentives.

Dietary Fat Intake and the Risk of Metabolic Syndrome in Korean Adults.

BACKGROUND: The effect of dietary fat intake on the risk of cardiovascular disease remains unclear. We investigated the association between dietary fat and specific types of fat intake and the risk of metabolic syndrome. METHODS: The study population included 1,662 healthy adults who were 50.2 years of age and had no known hypertension, diabetes, hyperlipidemia, or metabolic syndrome at the initial visit. Dietary intake was obtained from a 1-day food record. During 20.7 months of follow-up, we documented 147 cases of metabolic syndrome confirmed by self-report, anthropometric data, and blood test results. The intakes of total fat, vegetable fat, animal fat, saturated fatty acid (SFA), polyunsaturated fatty acid (PUFA), monounsaturated fatty acid (MUFA), and cholesterol level divided by quintile. Multivariate analyses included age, sex, body mass index, smoking status, alcohol intake, physical activity, total calorie, and protein intake. RESULTS: Vegetable fat intake was inversely associated with metabolic syndrome risk (odds ratio for the highest vs. the lowest quintile, 0.33; 95% confidence interval, 0.14 to 0.76). Total fat, animal fat, SFA, PUFA, MUFA, and cholesterol intakes showed no association with metabolic syndrome. Vegetable fat intake was inversely associated with the risk of hypertriglyceridemia among the components of metabolic syndrome. CONCLUSION: These data support an inverse association between vegetable fat and the risk of metabolic syndrome.

Increased bone mineral density according to increase of skeletal muscle mass in 534 Korean women: A retrospective cohort study conducted over 2.7 years.

OBJECTIVE: To determine the impact of the changes in the amount of abdominal fat, directly measured by computed tomography, body composition, and the metabolic syndrome (MetS) risk factors on the bone mineral density (BMD) of Korean women. METHODS: A retrospective cohort study involving 534 Korean women aged 29 to 78 years, who had undergone both dual-energy X-ray absorptiometry and abdominal adipose tissue analysis by computed tomography scan more than twice between January 2004 and December 2010. The changes in the BMD values were examined in association with the changes in fat amount, body composition parameters, and risk factors of MetS. RESULTS: On cross sectional analysis, there was a significant positive correlation between femoral BMD and total abdominal fat amount at the initial visit. However, the correlation disappeared when the impact of change of the fat amount on the change in BMD was analyzed over the study period. When the MetS and body composition parameters were analyzed, a significantly positive correlation was found between skeletal muscle mass and BMD. There was no significant relationship between the MetS risk factors or other body composition parameters and BMD throughout the study period after adjusting for age (time interval). CONCLUSION: Among body composition parameters, only increased skeletal muscle mass had a positive correlation with increased BMD over the study period of 2.7 years.

Association between metabolic syndrome and Helicobacter pylori infection diagnosed by histologic status and serological status.

GOALS: We aimed to simultaneously evaluate the association between metabolic syndrome and Helicobacter pylori (HP) infection diagnosed histologically and serologically in a large number of healthy Korean adults. BACKGROUND: Serological positivity for HP does not necessarily indicate current infection. No study to date has compared the association between metabolic syndrome and HP infection diagnosed by histologic and serological status. STUDY: HP status was ascertained histologically and serologically in healthy Korean adults who underwent comprehensive health screening in a private health screening center in Korea. Metabolic syndrome was defined according to the International Diabetes Federation definition. Multivariate logistic analyses were performed, after adjusting for potential confounders, including age, sex, smoking, alcohol consumption, and income level. RESULTS: A total of 5889 subjects were included in the analysis. The metabolic syndrome was more strongly associated with histologic positivity for HP [adjusted odds ratio (aOR)=1.26; 95% confidence interval (CI), 1.08-1.48] than serologic positivity (aOR=1.12, 95% CI, 0.95-1.32), after adjusting for age, sex, smoking status, alcohol consumption, and economic status. CONCLUSIONS: The stronger association between metabolic syndrome and histologic positivity than serological positivity suggests that the effects of HP infection on the pathogenesis of cardiometabolic outcomes may be reversible. Further prospective studies are needed.

Lack of Association between Self-reported Saltiness of Eating and Actual Salt Intake.

BACKGROUND: Reducing salt intake is known to be an important factor for lowering blood pressure and preventing cardiovascular disease. Estimating amount of salt intake is a necessary step towards salt intake reduction. Self-reported saltiness of diet is a method most easily used to measure a patient's salt intake. The purpose of this study was to examine the value of self-reported saltiness of diet in measuring salt intake. METHODS: We used data from 681 participants who visited a health center at a university hospital between August 2003 and November 2005. A self-administered questionnaire was used to collect information on self-reported saltiness of diet, other dietary habits and lifestyle factors. Salt intake was estimated on the basis of 24-hour dietary recall with a computer-aided nutritional analysis program (CAN-Pro 2.0, Korean Nutrition Society). RESULTS: There was no statistically significant difference between the mean salt intake of the self-reported salty diet group (13.7 ± 4.8 g/d) and the self-reported unsalty diet group (13.3 ± 4.4 g/d). If we assume calculated salt intake as the gold standard, the sensitivity and specificity of self-reported saltiness were 39.5% and 63.6%, respectively. Salt intake was increased with higher calorie intake, frequency of eating breakfast (≥5 times/wk) and being satiated with usual diet in men, but it was increased only with higher calorie intake in women. Regardless of actual salt intake, the group satiated with a usual diet tended to be in the group of self-reported salty diet. CONCLUSION: Self-reported saltiness of diet was not associated with actual salt intake. Further studies will be needed on the simpler and more objective tools to estimate salt intake.

Associations of smoking and smoking cessation with CT-measured visceral obesity in 4656 Korean men.

OBJECTIVES: Although obesity is shown to be less common among current smokers than never smokers, the association between visceral obesity and smoking remains uncertain. METHODS: For this cross-sectional analysis, we recruited 4656 Korean men of 19 to 79 years who received a regular checkup at a health examination center between 2008 and 2010. Computed tomography was performed to measure the area of visceral and subcutaneous adipose tissue (VAT and SAT). We compared the mean VAT by multiple regression analysis across smoking status after adjusting for confounders. RESULTS: Both current and former smokers had more mean VAT than never smokers. Current smokers who consumed more than 20 cigarettes per day had 11% higher mean VAT than never smokers (P<0.01). Longer smoking duration, higher daily cigarette consumption before quitting, and shorter abstinence duration among ex-smokers were associated with increasing mean VAT (all P for trend<0.01). The mean VAT in former smokers was highest within 2 years of abstinence. There was no significant difference of mean VAT between ex-smokers with >20 years of abstinence duration and never smokers. CONCLUSION: Both current and former smoking is associated with increased VAT. The risk of visceral obesity is proportional to the degree of exposure to cigarette smoking.

No significant association of aspirin use with cerebral microbleeds in the asymptomatic elderly.

BACKGROUND AND PURPOSE: Cerebral microbleeds (CMBs) may predict future risk for intracerebral hemorrhage (ICH). ICH is one of the most important complications of aspirin use. The association between aspirin use and CMBs is still controversial. In this context, we sought to investigate whether aspirin use is associated with CMBs in subjects without previous history of stroke. METHODS: Asymptomatic elderly subjects (n=1452; age ≥ 65 years) who visited for routine health check-ups were included in this study. CMBs were evaluated through T2*-weighted gradient-recalled echo MRI. Information about aspirin or warfarin use was obtained using a structured questionnaire. RESULTS: A total of 138 subjects (9.5%) were found to have CMBs. In the group of aspirin use, 43 subjects (11.2%) had CMBs; among them 9 (2.3%) had strictly lobar microbleeds and 34 (8.9%) had deep or infratentorial microbleeds. Compared with the non-use group, the risk for CMBs did not increase in the group of aspirin use (adjusted odds ratio, 1.10; 95% confidence interval, 0.73-1.66). For the group of aspirin use above 5 years, the proportion of CMBs (11.1%) did not increase compared with the group of short-term use (≤ 5 years, 9.5%, p=0.99) and non-use group (8.9%, p=0.66). CONCLUSIONS: We found that the prevalence of CMBs did not increase in the group of aspirin use, and the presence of CMBs was not associated with the duration of aspirin use in asymptomatic elderly subjects without a history of stroke or transient ischemic attack.

Association of obesity with cerebral microbleeds in neurologically asymptomatic elderly subjects.

Obesity is associated with an increased risk of cardiovascular disease, but few studies have investigated the effects of obesity on subclinical cerebrovascular disease. Cerebral microbleeds (CMBs) are radiological markers of cerebral small vessel disease and reflect underlying vasculopathy. In this context, we assessed whether obesity was related to CMBs and to CMB subtypes categorized by location. Neurologically asymptomatic elderly subjects (n = 1,251; age ≥ 65 years) who visited for routine health check-ups were included in this study. Cerebral microbleeds were evaluated through T2*-weighted gradient-recalled echo MRI. The subjects were categorized into two groups depending on CMB location: strictly lobar and deep or infratentorial microbleeds. Body mass index was calculated, and obesity was defined using the World Health Organization Western Pacific Regional Office criteria. A total of 120 (9.6 %) subjects were found to have CMBs. As the severity of obesity increased, the prevalence of CMBs increased. Compared with the normal weight group and after controlling possible confounders, the risk of deep or infratentorial microbleeds was significantly increased in the overweight group [odds ratio (OR) 2.32, 95 % confidence interval (CI) 1.19-4.53], and the obese group (OR 2.17, 95 % CI 1.14-4.13). However, the ORs for the strictly lobar microbleeds were not increased in either the overweight or obese groups. Obesity was associated with deep or infratentorial microbleeds. This finding suggests that obesity affects cerebral small vessels through arteriosclerotic vasculopathy. Based on our findings, we postulate that obesity is associated with the presence of subclinical and bleeding-prone cerebrovascular disease in the elderly.

Effect of central obesity on prostate specific antigen measured by computerized tomography: related markers and prostate volume.

PURPOSE: We assessed the effects of central adiposity represented by visceral adipose tissue on prostate volume, prostate specific antigen, and prostate specific antigen mass and mass ratio. MATERIALS AND METHODS: This cross-sectional study included 6,389 Asian men 30 to 79 years old. Prostate volume was estimated by transrectal ultrasound. Visceral and subcutaneous adipose tissue was measured by computerized tomography. Multivariate linear regression analysis was done between prostate specific antigen related variables and obesity indexes such as body mass index, waist circumference, and visceral and subcutaneous adipose tissue after adjusting for age. RESULTS: Body mass index, waist circumference and subcutaneous adipose tissue were inversely associated with prostate specific antigen (p for trend <0.001) but visceral adipose tissue showed no associations with prostate specific antigen (p for trend = 0.740). Waist circumference, and visceral and subcutaneous adipose tissue were positively associated with prostate specific antigen mass (p for trend = 0.014, <0.001 and 0.036, respectively). However, body mass index did not show this association (p for trend = 0.372). Body mass index, waist circumference and subcutaneous adipose tissue negatively affected the prostate specific antigen mass ratio (each p for trend <0.05) but there was no such significant correlation for visceral adipose tissue (p for trend = 0.187). When adjusted for visceral adipose tissue body mass index was not associated with prostate volume (p for trend = 0.152) but visceral adipose tissue remained positively associated with prostate volume even after adjusting for body mass index (p for trend = 0.005). CONCLUSIONS: Visceral adiposity is the main determining factor of the prostate volume increase and prostate specific antigen production.

Impact of visceral adiposity measured by abdominal computed tomography on pulmonary function.

Although an inverse relationship between abdominal adiposity and pulmonary function has been suggested, direct measurement of abdominal adipose tissue has rarely been attempted. Our object is to determine the impact of abdominal adiposity on pulmonary function by directly measuring abdominal adipose tissue with abdominal computed tomography (CT). In this cross-sectional study, we included never-smokers between the ages of 18 and 85 yr, who had undergone spirometry and abdominal adipose tissue analysis with CT scans during November 1, 2005 to October 31, 2009 as part of the comprehensive health examination. Among a total of 3,469 participants, 890 (25.7%) were male. The mean body mass index and waist circumference among males and females were 24.6 kg/m(2) and 87.8 cm and 23.0 kg/m(2) and 83.0 cm, respectively. Although total adipose tissue (TAT) of the abdomen in males (269.1 cm(2)) was similar to that in females (273.6 cm(2)), the ratio of visceral adipose tissue (VAT)/subcutaneous adipose tissue (SAT) was different; 0.99 in males and 0.50 in females. In males, TAT, SAT, and VAT were inversely associated with the absolute value of forced vital capacity (FVC), and TAT and VAT were inversely associated with forced expiratory volume in one second (FEV(1)). However, in females, TAT and VAT, but not SAT, were inversely associated with absolute FVC and FEV(1) values. In conclusion, the amount of abdominal adipose tissue directly measured using CT is inversely associated with lung function.

Metabolic syndrome and accompanying hyperinsulinemia have favorable effects on lower urinary tract symptoms in a generally healthy screened population.

PURPOSE: We assessed the association of metabolic syndrome, insulin resistance and lower urinary tract symptoms in a large, screened adult population. MATERIALS AND METHODS: We analyzed 33,841 Korean men 30 years old or older who underwent routine health assessments from October 2003 to February 2010. Metabolic syndrome was defined according to the modified Adult Treatment Panel III guidelines. Lower urinary tract symptoms were assessed using the International Prostate Symptom Score. Blood samples were drawn in the morning after patients had fasted at least 12 hours. RESULTS: Lower urinary tract symptoms had a marginally negative association with metabolic syndrome after adjusting for age (p = 0.045). This negative association became more significant as the number of metabolic syndrome components increased (p trend <0.01), especially voiding symptoms (p trend <0.01). Increasing the level of fasting insulin and the severity of insulin resistance were associated with a lower age adjusted OR for lower urinary tract symptoms (p <0.01 and 0.03, respectively). However, the diabetes group with high HbA1c (8.0% or greater) had a higher age adjusted OR for lower urinary tract symptoms, especially storage symptoms. The group with metabolic syndrome plus insulin resistance had lower total International Prostate Symptom Score, voiding symptoms, storage symptoms and quality of life scores than those without metabolic syndrome and/or insulin resistance (p <0.01, 0.01, 0.047 and 0.03, respectively). CONCLUSIONS: Metabolic syndrome, insulin resistance and the accompanying hyperinsulinemia may have favorable effects on lower urinary tract symptoms in the early compensatory stage, especially voiding symptoms. However, advanced diabetes may have unfavorable effects on lower urinary tract symptoms, especially storage symptoms. Hyperinsulinemia in patients with metabolic syndrome or insulin resistance may be a key factor in this phenomenon.

The illusion of prostate-specific antigen decline in patients with metabolic syndrome and insulin resistance.

UNLABELLED: What's known on the subject? and What does the study add? Studies have shown that PSA is negatively associated with obesity as a result of hemodilution or metabolic effect. Hemodilution could be the main reason for low PSA levels in obese men. However, the intrinsic metabolic effects such as insulin resistance (IR) or metabolic syndrome (MS) on PSA level have not been clearly evaluated although obesity is closely tied to MS and IR. We regarded MS and IR as the pathophysiological cornerstone of metabolic disorder in obesity and analyzed the relationships among MS, IR, and PSA levels, and plasma volume by using the concept of PSA mass, the total circulating PSA protein. PSA mass did not change depending on the severity of the obesity, MS or IR. Even the group with both MS and IR, which could be the most metabolically disturbed in this study, did not have different PSA mass, comparing with the group without any MS or IR. Thus, the decline in PSA level in men with MS or IR can be also explained by increased plasma volume other than any intrinsic metabolic effects. OBJECTIVE: • To investigate the detailed mechanism of prostate-specific antigen (PSA) decline in metabolic syndrome (MS) and insulin resistance (IR), which lowers the predictive value of the PSA test, we examined the effect of haemodilution and the possibility of an intrinsic metabolic effect. PATIENTS AND METHODS: • We analysed 28,315 men who underwent routine check-ups. We compared the age-adjusted mean PSA levels in subjects with and without MS before and after adjusting or stratifying the plasma volume. We analysed changes in PSA level, plasma volume and PSA mass according to obesity grade, number of MS components, IR severity and diagnosis of MS, IR or both using an analysis of covariance. RESULTS: • The PSA levels were lower in the group with MS than in the group without MS (P= 0.001), but this difference disappeared after adjusting or stratifying the plasma volume (P > 0.05 for all). The PSA levels decreased, plasma volume increased, and PSA mass did not change as the number of MS components increased (P= 0.002, P < 0.001, P= 0.55, respectively) or the IR severity increased (P= 0.001, P < 0.001, P= 0.34, respectively). • Similarly, PSA levels were lower, plasma volumes were higher and PSA masses were the same in subjects with MS (P= 0.002, P < 0.001, P= 0.10, respectively), IR (P= 0.018, P < 0.001, P= 0.94, respectively), or both (P= 0.003, P < 0.001, P= 0.86, respectively) than in subjects without those conditions. CONCLUSION: • The PSA decline in MS and IR may result simply from a haemodilution effect and be unrelated to intrinsic metabolic disturbances. For this reason, PSA levels could be underestimated in patients with MS or IR because of haemodilution.

Milk intake and its association with metabolic syndrome in Korean: analysis of the third Korea National Health and Nutrition Examination Survey (KNHANES III).

Although previous studies have shown that milk intake has some protective effects on metabolic syndrome (MS), there are few data on the relation between MS and milk consumption in Korean. To evaluate the association between milk intake frequency and MS, 4,890 subjects (2,052 men and 2,838 women) were included in the analysis, based on the national data from representative random sample of the third Korea National Health and Nutrition Examination Survey (KNHANES III) in 2005. We conducted both univariate and multivariate logistic regression analysis with adjustment for confounding factors associated with MS. Mean (±SD) age of subjects was 47.1±15.5 yr. In univariate analysis, the risk of MS was inversely associated with the frequency of milk intake, but this relation was attenuated in multivariate regression. In the individuals with BMI ≥23 kg/m(2), those with highest quartile of milk consumption (once daily or more) had significantly lower risk of MS (OR [95% CI] 0.72 [0.57-0.92] compared with lowest quartile [those rarely consumed]) after adjustment, but not among leaner individuals (BMI <23 kg/m(2)). Korean overweight adults who drink milk more frequently may be protected against MS. But it seems that this relation is somewhat different among MS components.

Prostate specific antigen mass ratio potential as a prostate cancer screening tool.

PURPOSE: Studies suggest lowering the threshold of the prostate specific antigen test in obese men due to the hemodilution effect but prostate specific antigen may be affected by prostate volume and insulin resistance, which also increase with obesity. Thus, we examined the combined effect of these factors on prostate specific antigen. MATERIALS AND METHODS: We analyzed 3,461 Korean men 30 to 80 years old with prostate volume data available who underwent routine evaluation. We examined the effect of plasma volume, homeostatic model assessment index, prostate volume and body mass index on prostate specific antigen, and prostate specific antigen mass and mass ratio (total circulating prostate specific antigen protein per prostate volume) by the trend test and/or ANOVA after adjusting for age and/or prostate volume. RESULTS: Body mass index had positive associations with plasma volume, the homeostatic model assessment index and prostate volume (p for trend <0.01). Prostate specific antigen had a positive association with prostate volume and a negative association with plasma volume (p for trend <0.01) but not with homeostatic model assessment index. The adjusted R(2) of prostate volume vs prostate specific antigen was greater than for plasma volume vs prostate specific antigen while for body mass index vs prostate volume it was less than for body mass index vs plasma volume (0.0892, 0.0235, 0.1346 and 0.3360, respectively). Prostate specific antigen mass was not associated with plasma volume or body mass index but it was still associated with prostate volume after adjusting for plasma volume or body mass index (p for trend <0.01). Mean prostate specific antigen mass ratio did not change significantly across body mass index, plasma volume or prostate volume quartiles in men older than 55 years. CONCLUSIONS: It is not logical to lower the prostate specific antigen threshold based on only the hemodilution effect since body mass index related prostate volume enlargement can increase prostate specific antigen in obese men. Another tool is needed and prostate specific antigen mass ratio may be an option.

Effect of body mass index and waist circumference on prostate specific antigen and prostate volume in a generally healthy Korean population.

PURPOSE: We examined the influences of age, body mass index and waist circumference on prostate specific antigen before and after adjusting for prostate volume. We also examined associations among age, body mass index, waist circumference and prostate volume. MATERIALS AND METHODS: We analyzed 38,380 Korean men 30 to 79 years old who received regular checkups at our health examination center. We had prostate volume data for 3,593 of them. We divided the subjects into 5 groups by age, 4 groups by body mass index and waist circumference (using Asia-Pacific obesity reference values), and quartiles for prostate volume. We compared prostate specific antigen and prostate volume by multivariate regression analysis across body mass index and waist circumference after adjusting for age and/or prostate volume. RESULTS: Increasing body mass index or waist circumference was associated with decreasing prostate specific antigen (with or without prostate volume adjustment) and increasing prostate volume (p for trend <0.01). When we stratified prostate volume by quartile, age was not associated with prostate specific antigen except in quartile 4 (p for trend by quartile 0.402, 0.639, 0.056 and <0.01). Mean prostate specific antigen of the group with a body mass index less than 23 in prostate volume quartile 4 was approximately 3 times that of the group with a body mass index greater than 30 in prostate volume quartile 1 (1.42 vs 0.55). CONCLUSIONS: Obesity had a negative association with prostate specific antigen regardless of prostate volume, and a positive association with prostate volume. Age was not associated with prostate specific antigen after prostate volume adjustment. Obese men, especially those with a small prostate volume, may have lower baseline prostate specific antigen and, thus, be at higher risk for having prostate cancer undetected in a prostate specific antigen screening test.