Marginal structural models for case-cohort study designs to estimate the association of antiretroviral therapy initiation with incident AIDS or death

To estimate the association of antiretroviral therapy initiation with incident acquired immunodeficiency syndrome (AIDS) or death while accounting for time-varying confounding in a cost-efficient manner, the authors combined a case-cohort study design with inverse probability-weighted estimation of a marginal structural Cox proportional hazards model. A total of 950 adults who were positive for human immunodeficiency virus type 1 were followed in 2 US cohort studies between 1995 and 2007. In the full cohort, 211 AIDS cases or deaths occurred during 4,456 person-years. In an illustrative 20% random subcohort of 190 participants, 41 AIDS cases or deaths occurred during 861 person-years. Accounting for measured confounders and determinants of dropout by inverse probability weighting, the full cohort hazard ratio was 0.41 (95% confidence interval: 0.26, 0.65) and the case-cohort hazard ratio was 0.47 (95% confidence interval: 0.26, 0.83). Standard multivariable-adjusted hazard ratios were closer to the null, regardless of study design. The precision lost with the case-cohort design was modest given the cost savings. Results from Monte Carlo simulations demonstrated that the proposed approach yields approximately unbiased estimates of the hazard ratio with appropriate confidence interval coverage. Marginal structural model analysis of case-cohort study designs provides a cost-efficient design coupled with an accurate analytic method for research settings in which there is time-varying confounding.     

Effect of tuberculosis on the survival of women infected with human immunodeficiency virus

Evidence regarding the effect of tuberculosis (TB) disease on progression of human immunodeficiency virus (HIV) disease is inconclusive. The authors estimated the effect of time-varying incident TB on time to acquired immunodeficiency syndrome (AIDS)-related mortality using a joint marginal structural Cox model. Between 1995 and 2002, 1,412 HIV type 1 (HIV-1)-infected women enrolled in the Women's Interagency HIV Study were followed for a median of 6 years. Twenty-nine women incurred incident TB, and 222 died of AIDS-related causes. Accounting for age, CD4 cell count, HIV-1 RNA level, serum albumin level, and non-TB AIDS at study entry, as well as for time-varying CD4 cell count, CD4 cell count nadir, HIV-1 RNA level, peak HIV-1 RNA level, serum albumin level, HIV-related symptoms, non-TB AIDS, anti-Pneumocystis jiroveci prophylaxis, antiretroviral therapy, and household income, the hazard ratio for AIDS-related death comparing time after incident TB with time before incident TB was 4.0 (95% confidence interval (CI): 1.2, 14). The effect of incident TB on mortality was similar among highly active antiretroviral therapy (HAART)-exposed women (hazard ratio = 4.3, 95% CI: 0.9, 22) and non-HAART-exposed women (hazard ratio = 3.9, 95% CI: 0.9, 17; interaction p = 0.91). Although results were imprecise because few women incurred TB, irrespective of HAART exposure, incident TB increases the hazard of AIDS-related death among HIV-infected women.     

Serum albumin level as a predictor of incident coronary heart disease: the Atherosclerosis Risk in Communities (ARIC) study

Various studies have reported an inverse association between serum albumin level and incident coronary heart disease (CHD), though biologic mechanisms have not been established. The authors examined the association between serum albumin level and CHD in the Atherosclerosis Risk in Communities cohort, comprising 14,506 White and African-American middle-aged men and women. The mean albumin level in this population was 3.9 g/dl (standard deviation 0.3). During 5.2 years of follow-up, 470 incident CHD events occurred. The hazard ratio for incident CHD associated with a 1-standard deviation decrease in serum albumin level was 1.26 (95% confidence interval (CI): 1.15, 1.38) after adjustment for age, gender, and ethnicity and 1.18 (95% CI: 1.07, 1.30) after additional adjustment for covariates related to CHD. Hazard ratios were similar across gender and ethnic groups. However, there was statistically significant effect modification by smoking status, with hazard ratios of 1.01 (95% CI: 0.84, 1.22) among never smokers, 1.09 (95% CI: 0.92, 1.30) among former smokers, and 1.35 (95% CI: 1.17, 1.54) among current smokers. Further adjustment for factors related to renal disease, nutrition, platelet aggregation, inflammation, use of angiotensin-converting enzyme inhibitors, and hemostasis factors attenuated the albumin-CHD relation only slightly. In this study, serum albumin was inversely associated with incident CHD at the baseline examination in current smokers but not in never or former smokers. Albumin level may be a marker of susceptibility to the inflammatory response that results from smoking.     

Familial tendency and risk of nasopharyngeal carcinoma in taiwan: effects of covariates on risk

In the present study, the authors compared the long-term risk of nasopharyngeal carcinoma (NPC) of male participants in an NPC multiplex family cohort with that of controls in a community cohort in Taiwan after adjustment for anti-Epstein-Barr virus (EBV) seromarkers and cigarette smoking. A total of 43 incident NPC cases were identified from the 1,019 males in the NPC multiplex family cohort and the 9,622 males in the community cohort, for a total of 8,061 person-years and 185,587 person-years, respectively. The adjusted hazard ratio was 6.8 (95% confidence interval (CI): 2.3, 20.1) for the multiplex family cohort compared with the community cohort. In the evaluation of anti-EBV viral capsid antigen immunoglobulin A and anti-EBV deoxyribonuclease, the adjusted hazard ratios were 2.8 (95% CI: 1.3, 6.0) and 15.1 (95% CI: 4.2, 54.1) for those positive for 1 EBV seromarker and positive for both seromarkers, respectively, compared with those negative for both EBV seromarkers. The adjusted hazard ratio was 31.0 (95% CI: 9.7, 98.7) for participants who reported a family history of NPC and who were anti-EBV-seropositive compared with individuals without such a history who were anti-EBV-seronegative. The findings suggest that both family history of NPC and anti-EBV seropositivity are important determinants of subsequent NPC risk and that the effect of family history on NPC risk cannot be fully explained by mediation through EBV serologic responses.     

Prevalence and determinants of high-risk human papillomavirus (HPV) infection and cervical cytological abnormalities in imprisoned women

The aim of the study was to estimate the prevalence and risk factors associated with infection by high-risk human papillomavirus (HR-HPV) in cervix and squamous intra-epithelial lesions (SIL) in imprisoned women. This was done by a cross-sectional study of imprisoned women attending the gynaecological clinic in Foncalent prison in Alicante, Spain. The study period was from May 2003 to December 2005. HR-HPV infection was determined through Digene HPV Test, Hybrid Capture II (HC-II). HPV typing was determined by multiplex nested PCR assay combining degenerate E6/E7 consensus primers. Multiple logistic regression modelling was used for the analysis of associations between variables where some were considered possible confounders after checking for interactions. A total of 219 women were studied. HR-HPV prevalence was 27.4% and prevalence of SIL was 13.3%. HIV prevalence was 18%, higher in Spaniards than in migrant women (24.6% vs. 14.3%, P<0.05). In multivariate analyses, risk factors for HPV infection were younger age (P for trend=0.001) and tobacco use (OR 2.62, 95% CI 1.01-6.73). HPV infection (OR 4.8, 95% CI 1.7-13.8) and HIV infection were associated with SIL (OR 4.8, 95% CI 1.6-14.1). The commonest HPV types were HPV16 (29.4%), HPV18 (17.6%), HPV39 (17.6%) and HPV68 (17.6%). The prevalence of both HR-HPV infection and SIL in imprisoned women found in this study is high. Determinants for each of the outcomes studied were different. HPV infection is the most important determinant for SIL. A strong effect of HIV co-infection on the prevalence of SIL has been detected. Our findings reinforce the need to support gynaecological clinics in the prison setting.     

Duration of lactation and incidence of maternal hypertension: a longitudinal cohort study

Never or curtailed lactation has been associated with an increased risk for incident hypertension, but the effect of exclusive breastfeeding is unknown. The authors conducted an observational cohort study of 55,636 parous women in the US Nurses' Health Study II. From 1991 to 2005, participants reported 8,861 cases of incident hypertension during 660,880 person-years of follow-up. Never or curtailed lactation was associated with an increased risk of incident hypertension. Compared with women who breastfed their first child for ≥12 months, women who did not breastfeed were more likely to develop hypertension (hazard ratio (HR) = 1.27, 95% confidence interval (CI): 1.18, 1.36), adjusting for family history and lifestyle covariates. Women who never breastfed were more likely to develop hypertension than women who exclusively breastfed their first child for ≥6 months (HR = 1.29, 95% CI: 1.20, 1.40). The authors found similar results for women who had never breastfed compared with those who had breastfed each child for an average of ≥12 months (HR = 1.22, 95% CI: 1.13, 1.32). In conclusion, never or curtailed lactation was associated with an increased risk of incident maternal hypertension, compared with the recommended ≥6 months of exclusive or ≥12 months of total lactation per child, in a large cohort of parous women.     

Alcohol intake, drinking patterns, and risk of prostate cancer in a large prospective cohort study

Alcohol drinking has been extensively studied in relation to prostate cancer, yet findings on the direction of the association are equivocal. Previous studies have not examined drinking patterns. Thus, the authors prospectively evaluated the associations between these factors and risk of incident prostate cancer (n = 2,479) in a cohort study of 47,843 US men (1986-1998). The men completed a questionnaire at baseline that included information on consumption of specific types of alcohol and frequency of use. The authors estimated hazard ratios using Cox proportional hazards regression for average alcohol intake and number of days per week on which alcohol was consumed stratified by average weekly intake (<105 g/week vs. > or = 105 g/week). Compared with nondrinking, the hazard ratio for consumption increased slightly from an average of 5.0-14.9 g/day (hazard ratio (HR) = 1.05, 95% confidence interval (CI): 0.94, 1.18) to 30.0-49.9 g/day (HR = 1.13, 95% CI: 0.96, 1.33), but it was not increased at > or = 50 g/day (HR = 1.00, 95% CI: 0.77, 1.31) after adjustment for recent smoking and other factors. Compared with abstainers, risk was greatest among men who consumed an average of > or = 105 g/week but who drank on only 1-2 days per week (HR = 1.64, 95% CI: 1.13, 2.38). These results suggest that moderate or greater alcohol consumption is not a strong contributor to prostate cancer risk, except possibly in men who consume large amounts infrequently.     

Determinants of clearance of human papillomavirus infections in Colombian women with normal cytology: a population-based, 5-year follow-up study

Little is known about the factors that influence clearance of human papillomavirus (HPV), the primary cause of cervical carcinoma. A total of 227 women cytologically normal and HPV positive at baseline were identified from a population-based cohort of 1,995 Bogota, Colombia, women aged 13-85 years followed between 1993 and 2000 (mean follow-up, 5.3 years). HPV DNA detection and viral load determination were based on a GP5+/GP6+ polymerase chain reaction enzyme immunoassay. Rate ratio estimates for HPV clearance were calculated by using methods for interval-censored survival time data. Analyses were based on 316 type-specific HPV infections. HPV 16 had a significantly lower clearance rate than infections with low-risk types (rate ratio (RR) = 0.47, 95% confidence interval (CI): 0.32, 0.72), HPV types related to HPV 16 (types 31, 33, 35, 52, 58) had intermediate clearance rates (RR = 0.62, 95% CI: 0.47, 0.94), and other high-risk types did not show evidence of slower clearance compared with low-risk types. Infections with single and multiple HPV types had similar clearance rates. There was no evidence of a dose-response relation between clearance and viral load. Observed was slower clearance in parous women (RR = 0.64, 95% CI: 0.47, 0.89) and faster clearance in ever users of oral contraceptives (RR = 1.38, 95% CI: 1.07, 1.77).     

A prospective study of arsenic exposure from drinking water and incidence of skin lesions in Bangladesh

Elevated concentrations of arsenic in groundwater pose a public health threat to millions of people worldwide. The authors aimed to evaluate the association between arsenic exposure and skin lesion incidence among participants in the Health Effects of Arsenic Longitudinal Study (HEALS). The analyses used data on 10,182 adults free of skin lesions at baseline through the third biennial follow-up of the cohort (2000-2009). Discrete-time hazard regression models were used to estimate hazard ratios and 95% confidence intervals for incident skin lesions. Multivariate-adjusted hazard ratios for incident skin lesions comparing 10.1-50.0, 50.1-100.0, 100.1-200.0, and ≥200.1 μg/L with ≤10.0 μg/L of well water arsenic exposure were 1.17 (95% confidence interval (CI): 0.92, 1.49), 1.69 (95% CI: 1.33, 2.14), 1.97 (95% CI: 1.58, 2.46), and 2.98 (95% CI: 2.40, 3.71), respectively (P(trend) = 0.0001). Results were similar for the other measures of arsenic exposure, and the increased risks remained unchanged with changes in exposure in recent years. Dose-dependent associations were more pronounced in females, but the incidence of skin lesions was greater in males and older individuals. Chronic arsenic exposure from drinking water was associated with increased incidence of skin lesions, even at low levels of arsenic exposure (<100 μg/L).     

Effect of highly active antiretroviral therapy on time to acquired immunodeficiency syndrome or death using marginal structural models

To estimate the net (i.e., overall) effect of highly active antiretroviral therapy (HAART) on time to acquired immunodeficiency syndrome (AIDS) or death, the authors used inverse probability-of-treatment weighted estimation of a marginal structural model, which can appropriately adjust for time-varying confounders affected by prior treatment or exposure. Human immunodeficiency virus (HIV)-positive men and women (n = 1,498) were followed in two ongoing cohort studies between 1995 and 2002. Sixty-one percent (n = 918) of the participants initiated HAART during 6,763 person-years of follow-up, and 382 developed AIDS or died. Strong confounding by indication for HAART was apparent; the unadjusted hazard ratio for AIDS or death was 0.98. The hazard ratio from a standard time-dependent Cox model that included time-varying CD4 cell count, HIV RNA level, and other time-varying and fixed covariates as regressors was 0.81 (95% confidence interval: 0.61, 1.07). In contrast, the hazard ratio from a marginal structural survival model was 0.54 (robust 95% confidence interval: 0.38, 0.78), suggesting a clinically meaningful net benefit of HAART. Standard Cox analysis failed to detect a clear net benefit, because it does not appropriately adjust for time-dependent covariates, such as HIV RNA level and CD4 cell count, that are simultaneously confounders and intermediate variables.     

Low plasma eicosapentaenoic acid and depressive symptomatology are independent predictors of dementia risk

BACKGROUND: The potential preventive role of polyunsaturated fatty acids (PUFAs) in Alzheimer disease has aroused increasing interest. Plasma n-3 PUFAs have been shown to be inversely related to the risk of dementia and to depression, which is frequently associated with dementia. OBJECTIVE: The objective was to ascertain whether plasma PUFAs predict the risk of incident dementia in a cohort of older persons, independently of their depressive status. DESIGN: Of 1214 nondemented participants in the Three-City Study from Bordeaux (France) who were followed up for 4 y, 65 developed dementia. The association between the proportion of plasma fatty acids at baseline and the risk of incident dementia was assessed by multivariate proportional hazard models, taking into account depressive status assessed on the basis of the Center for Epidemiologic Studies Depression scale. RESULTS: A higher plasma eicosapentaenoic acid (EPA) concentration was associated with a lower incidence of dementia [hazard ratio (HR) for 1 SD = 0.69; 95% CI: 0.48, 0.98], independently of depressive status and after adjustment for age, education, apolipoprotein E epsilon4 allele, diabetes, and baseline plasma vitamin E and triacylglycerol. The relations between docosahexaenoic acid (DHA), total n-3 PUFAs, and incident dementia did not remain significant in multivariate models. Higher ratios of arachidonic acid (AA) to DHA and of n-6 to n-3 fatty acids were related to an increased risk of dementia, particularly in depressive subjects (n = 90): ratio of AA to DHA (HR: 2.65; 95% CI: 1.07, 6.56) and ratio of n-6 to n-3 (HR: 1.61; 95% CI: 1.04, 2.47). CONCLUSIONS: A high plasma EPA concentration may decrease the risk of dementia, whereas high ratios of n-6 to n-3 fatty acids and of AA to DHA may increase the risk of dementia, especially in depressed older persons. The role of EPA in dementia warrants further research.     

Nonsteroidal antiinflammatory drugs and bladder cancer: a pooled analysis

Case-control studies have shown that regular use of nonsteroidal antiinflammatory drugs (NSAIDs) decreases bladder cancer risk, but few cohort studies have evaluated this association. The authors investigated NSAID use and bladder cancer in 3 large prospective studies (NIH-AARP Diet and Health Study; Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial; and U.S. Radiologic Technologists Study). Frequency of aspirin and nonaspirin NSAID use 1 year prior to baseline was ascertained using self-administered questionnaires. Study-specific hazard ratios and 95% confidence intervals were estimated using Cox regression models and were combined using a fixed-effects meta-analytic model. Data from all studies were aggregated, and aggregated hazard ratios were estimated. The analysis included 508,842 individuals, with 2,489 incident cases of bladder cancer. A reduction in risk was observed for individuals who reported regular use (>2 times/week) of nonaspirin NSAIDs compared with those who reported no use (hazard ratio (HR) = 0.92, 95% confidence interval (CI): 0.81, 1.04). The risk reduction was limited to nonsmokers (HR = 0.58, 95% CI: 0.41, 0.83) (P(trend) = 0.008) (P(interaction) = 0.02). No association was observed between regular aspirin use and bladder cancer risk (HR = 1.04, 95% CI: 0.94, 1.15). Results suggest that nonaspirin NSAIDs, but not aspirin, are associated with a reduction in risk of bladder cancer, particularly for nonsmokers.     

The association of drinking water quality and sewage disposal with Helicobacter pylori incidence in infants: the potential role of water-borne transmission

The mode of transmission of Helicobacter pylori, a bacterium causing gastric cancer and peptic ulcer disease, is unknown although waterborne transmission is a likely pathway. This study investigated the hypothesis that access to treated water and a sanitary sewerage system reduces the H. pylori incidence rate, using data from 472 participants in a cohort study that followed children in Juarez, Mexico, and El Paso, Texas, from April 1998, with caretaker interviews and the urea breath test for detecting H. pylori infection at target intervals of six months from birth through 24 months of age. The unadjusted hazard ratio comparing bottled/vending machine water to a municipal water supply was 0.71 (95% confidence interval (CI): 0.50, 1.01) and comparing a municipal sewer connection to a septic tank or cesspool, 0.85 (95% CI: 0.60, 1.20). After adjustment for maternal education and country, the hazard ratios decreased slightly to 0.70 (95% confidence interval: 0.49, 1.00) and 0.77 (95% confidence interval: 0.50, 1.21), respectively. These results provide moderate support for potential waterborne transmission of H. pylori.     

Dietary fiber intake in relation to coronary heart disease and all-cause mortality over 40 y: the Zutphen Study

BACKGROUND: Little is known about the effects of dietary fiber intake on long-term mortality. OBJECTIVE: We aimed to study recent and long-term dietary fiber intake in relation to coronary heart disease and all-cause mortality. DESIGN: The effects of recent and long-term dietary fiber intakes on mortality were investigated in the Zutphen Study, a cohort of 1,373 men born between 1900 and 1920 and examined repeatedly between 1960 and 2000. During that period, 1,130 men died, 348 as a result of coronary heart disease. Hazard ratios were obtained from time-dependent Cox regression models. RESULTS: Every additional 10 g of recent dietary fiber intake per day reduced coronary heart disease mortality by 17% (95% CI: 2%, 30%) and all-cause mortality by 9% (0%, 18%). The strength of the association between long-term dietary fiber intake and all-cause mortality decreased from age 50 y (hazard ratio: 0.71; 95% CI: 0.55, 0.93) until age 80 y (0.99; 0.87, 1.12). We observed no clear associations for different types of dietary fiber. CONCLUSIONS: A higher recent dietary fiber intake was associated with a lower risk of both coronary heart disease and all-cause mortality. For long-term intake, the strength of the association between dietary fiber and all-cause mortality decreased with increasing age.     

Smoking and time to clearance of human papillomavirus infection in HIV-seropositive and HIV-seronegative women

Persistent human papillomavirus (HPV) infection seems central to cervical carcinogenesis. Smoking is associated with cervical cancer in HPV DNA-positive women, but its association with HPV persistence is unclear, particularly with respect to human immunodeficiency virus (HIV) serostatus. The authors evaluated smoking and HPV clearance by HIV serostatus among 801 women from the HIV Epidemiology Research Study (United States, 1993-2000). Type-specific HPV duration was defined as the interval between initial MY09/11 polymerase chain reaction positivity and the first of two consecutive HPV-negative study visits. Hazard ratios adjusted for study site and risk behaviors (sexual activity or injection drug use) were estimated using Cox regression. This analysis included 522 HIV-seropositive and 279 HIV-seronegative women (median follow-up, 4.4 years). Ever smoking was associated with reduced clearance of high-risk HPV in HIV-seronegative women (hazard ratio (HR) = 0.51, 95% confidence interval (CI): 0.30, 0.88) but not in HIV-seropositive women (HR = 0.96, 95% CI: 0.65, 1.42); similar results were found for current smoking. Current smoking was not associated with clearance of any type-specific HPV in HIV-seropositive (HR = 0.99, 95% CI: 0.82, 1.20) or HIV-seronegative (HR = 0.93, 95% CI: 0.68, 1.26) women. HPV clearance did not appear to vary by amount or duration of smoking. Smoking did not modify overall clearance but was associated with lower high-risk HPV clearance in HIV-seronegative women.     

Myocardial infarction and future risk of cancer in the general population—the Tromsø Study

The association between myocardial infarction (MI) and future risk of incident cancer is scarcely investigated. Therefore, we aimed to study the risk of cancer after a first time MI in a large cohort recruited from a general population. Participants in a large population-based study without a previous history of MI or cancer (n = 28,763) were included and followed from baseline to date of cancer, death, migration or study end. Crude incidence rates (IRs) and hazard ratios (HRs) for cancer after MI were calculated. During a median follow-up of 15.7 years, 1747 subjects developed incident MI, and of these, 146 suffered from a subsequent cancer. In the multivariable-adjusted model (adjusted for age, sex, BMI, systolic blood pressure, diabetes mellitus, HDL cholesterol, smoking, physical activity and education level), MI patients had 46% (HR 1.46; 95% CI: 1.21–1.77) higher hazard ratio of cancer compared to those without MI. The increased cancer incidence was highest during the first 6 months after the MI, with a 2.2-fold higher HR (2.15; 95% CI: 1.29–3.58) compared with subjects without MI. After a 2-year period without higher incidence rate, MI patients displayed 60% (HR 1.60; 95% CI: 1.27–2.03) higher HR of future cancer more than 3 years after the event. The increased IRs were higher in women than men. Patients with MI had a higher short- and long-term incidence rate of cancer compared to subjects without MI. Our findings suggest that occult cancer and shared risk factors of MI and cancer may partly explain the association.     

Dose-specific meta-analysis and sensitivity analysis of the relation between alcohol consumption and lung cancer risk

Alcohol drinking increases the risk of several types of cancer, but studies of the relation between alcohol and lung cancer risk are complicated by smoking. The authors carried out meta-analyses for four study designs and conducted sensitivity analyses to assess the results. Pooled smoking-unadjusted relative risks (RRs) for brewery workers and alcoholics were 1.17 (95% confidence interval (CI): 0.99, 1.39) and 1.99 (95% CI: 1.66, 2.39), respectively, relative to population rates. For cohort and case-control studies, the authors conducted dose-specific meta-analyses for ethanol consumption of 1-499, 500-999, 1,000-1,999, and > or = 2,000 g/month, relative to nondrinking. Smoking-adjusted RRs for ascending dose groups in cohort studies were 0.98 (95% CI: 0.79, 1.21), 0.92 (95% CI: 0.81, 1.04), 1.04 (95% CI: 0.88, 1.22), and 1.53 (95% CI: 1.04, 2.25), respectively. Smoking-adjusted odds ratios for ascending groups in case-control studies were 0.63 (95% CI: 0.51, 0.78), 1.30 (95% CI: 0.98, 1.70), 1.13 (95% CI: 0.46, 2.75), and 1.86 (95% CI: 1.39, 2.49), respectively. Elevated odds ratios were seen for hospital-based case-control studies but not for population-based case-control studies. Sensitivity analyses indicated that smoking explained the elevated RRs in studies of alcoholics and that strong misclassification of smoking status could produce an elevated smoking-adjusted RR in cohort and case-control studies. Overall, evidence for a smoking-adjusted association between alcohol and lung cancer risk is limited to very high consumption groups in cohort and hospital-based case-control studies. At lower levels, any associations observed appear to be explained by confounding.     

Indications for and use of nonsteroidal antiinflammatory drugs and the risk of incident, symptomatic benign prostatic hyperplasia: results from the prostate cancer prevention trial

The authors conducted a cohort study of nonsteroidal antiinflammatory drug (NSAID) use and risk of symptomatic benign prostatic hyperplasia (BPH), using data from 4,735 men without BPH at baseline in the placebo arm of the Prostate Cancer Prevention Trial (1993-2003). Incident BPH (n = 471) was defined as medical or surgical treatment or at least 2 International Prostate Symptom Score (I-PSS) values greater than or equal to 15. Proportional hazards models using time-dependent exposure for NSAID use were employed to estimate covariate-adjusted associations of NSAID-related medical conditions and NSAID use with BPH risk. Arthritis, other inflammation-related musculoskeletal conditions, and headaches were associated with increased BPH risk (hazard ratio (HR) = 1.77 (95% confidence interval (CI): 1.37, 2.29), HR = 1.57 (95% CI: 1.14, 2.17), and HR = 1.40 (95% CI: 1.09, 1.80), respectively). Use of any NSAID, use of aspirin, and use of nonaspirin NSAIDs were associated with significant increases in BPH risk (HR = 1.21 (95% CI: 1.01, 1.46), HR = 1.20 (95% CI: 1.00, 1.45), and HR = 1.34 (95% CI: 1.07, 1.69), respectively). Control for indications for NSAID use, including baseline I-PSS, attenuated the associations slightly, but all became nonsignificant. Among men with no indications for NSAID use, the hazard ratio for any NSAID use was 1.06 (95% CI: 0.82, 1.38). The modest associations of NSAID use with BPH risk in this cohort were probably due to confounding by indication, and NSAID use was not associated with BPH risk.     

Determinants of squamous intraepithelial lesions (SIL) on Pap smear: The role of HPV infection and of HIV-1-induced immunosuppression

This study aimed to identify risk factors for squamous intraepithelial lesions (SIL) in women with known HIV status and to explore the association between SIL, HPV subtype, and HIV-induced immunosuppression. The study population consisted of women with known HIV serological status who were attending a network of 16 clinical centres in Italy. Detailed behavioural data, clinical and laboratory parameters, and samples for diagnosis of SIL by Papanicolau smear and HPV infection using a polymerase chain reaction (PCR) were obtained from each study participant. The strength of the association between SIL and possible risk factors was assessed calculating crude and adjusted odds ratios derived from univariate analysis and multivariate models. We enrolled 236 women, of whom 135 (57.2%) were HIV-infected. SIL was diagnosed in 57 women (24.1%); of these, 48 (35.6%) were HIV-infected and 9 (8.9%) were HIV-negative. HPV-DNA was detected in 41 (72%) women with SIL and in 45 (25%) women without SIL. HPV-DNA was more often detected among HIV-infected women than among HIV-negative women (40% vs. 32%), but the difference was not statistically significant. Women infected with high-risk types or with low-risk-uncharacterised types of HPV both had a higher risk of SIL compared with HPV-negative women (respectively, AOR: 17.53 and AOR: 2.89). HIV-infected women with severe or moderate immunosuppression were more likely to have SIL than HIV-negative women (respectively, AOR: 7.29 and AOR: 3.09) also independently from HPV infection. Women reporting use of a contraceptive pill had a 2.5 times higher risk of SIL compared with those who never used hormonal contraceptives. The results confirm that high-risk HPV types are strongly associated with SIL, and that HIV infection may strengthen the effect of HPV at cervical level. The use of oral contraceptives may slightly increase the risk of SIL in women with at-risk behaviour for HIV infection.     

Job strain and risk of musculoskeletal symptoms among a prospective cohort of occupational computer users

OBJECTIVES: Most previous studies of the association between psychosocial stress and musculoskeletal illness among computer users have been cross-sectional and have yielded inconsistent results. The association between a measure of psychosocial stress, "job strain", and incident neck-shoulder and arm-hand musculoskeletal symptoms was investigated among recently hired computer users. METHODS: The participants worked for one of several large employers and were followed prospectively for 6 months. The "job demands" and "decision latitude" subscales of the Job Content Questionnaire were used to estimate the job-strain quadrants and a ratio measure of job strain which was subsequently categorized. Incident musculoskeletal symptoms were obtained with weekly diaries. Proportional hazards models were used to estimate associations between job strain and incident musculoskeletal symptoms. RESULTS: Those in the high-strain quadrant were at increased risk of neck-shoulder symptoms [hazard ratio (HR) 1.65, 95% confidence interval (95% CI) 0.91-2.99] when compared with those in the low-strain quadrant. Those in the highest strain-ratio category were also at increased risk of neck-shoulder symptoms when compared with those in the lowest strain-ratio category (HR 1.52, 95% CI 0.88-2.62). Modification by previous years of computer use was observed, with an elevated risk observed for those in the highest job-strain ratio category who also had low previous computer use (HR 3.16, 95% CI 1.25-8.00). There did not appear to be an association between either measure of job strain and incident arm-hand symptoms. CONCLUSIONS: In this cohort, workers who reported high job strain were more likely to develop neck-shoulder symptoms.