Variables dépendantes du temps dans le modèle de Cox Théorie et pratique

Comparison of cohort and nested case-control designs for estimating the effect of time-varying drug exposure on the risk of adverse event in the presence of ties

Cohort and nested case-control (NCC) designs are frequently used in pharmacoepidemiology to assess the associations of drug exposure that can vary over time with the risk of an adverse event. Although it is typically expected that estimates from NCC analyses are similar to those from the full cohort analysis, with moderate loss of precision, only few studies have actually compared their respective performance for estimating the effects of time-varying exposures (TVE). We used simulations to compare the properties of the resulting estimators of these designs for both time-invariant exposure and TVE. We varied exposure prevalence, proportion of subjects experiencing the event, hazard ratio, and control-to-case ratio and considered matching on confounders. Using both designs, we also estimated the real-world associations of time-invariant ever use of menopausal hormone therapy (MHT) at baseline and updated, time-varying MHT use with breast cancer incidence. In all simulated scenarios, the cohort-based estimates had small relative bias and greater precision than the NCC design. NCC estimates displayed bias to the null that decreased with a greater number of controls per case. This bias markedly increased with higher proportion of events. Bias was seen with Breslow's and Efron's approximations for handling tied event times but was greatly reduced with the exact method or when NCC analyses were matched on confounders. When analyzing the MHT-breast cancer association, differences between the two designs were consistent with simulated data. Once ties were taken correctly into account, NCC estimates were very similar to those of the full cohort analysis.

Time-dependent lymphocyte count after transplantation is associated with higher risk of graft failure and death

The transplantation field requires the identification of specific risk factors associated with the level of immunosuppression. Here, our aim was to analyze the association between the number of circulating lymphocytes, monitored routinely by complete blood cell counts during outpatient visits, and patient and graft survival. In total, 2,999 kidney or combined kidney-pancreas recipients transplanted between 2000 and 2016, from two University hospitals, were enrolled. We investigated the etiological relationship between time-dependent lymphocyte count beyond one year after transplantation and patient and graft survival, viral infection and cancer risk using time-dependent multivariate Cox models. Model 1 considered kidney function at one year and model 2 as time-dependent variable. At the time of inclusion (one year after transplantation), 584 patients (19.4%) had deep lymphopenia (under 750 /mm³) and 1,072 (35.7%) had a normal count (over 1,500 /mm³). A patient with deep lymphopenia at a given follow-up time had significantly higher risks of graft failure, death and viral infection than comparable patients with a normal lymphocyte count at the same time point. Thus, after the first year of transplantation, the occurrence of deep lymphopenia within a patient's follow-up is a risk factor for long-term graft failure, death and viral infection.

Psychiatric Adverse Events Associated With Infliximab: A Cohort Study From the French Nationwide Discharge Abstract Database

Introduction

Infliximab (IFX) was the first anti-tumor necrosis factor (TNFα) antibody to be used in the treatment of severe chronic inflammatory diseases, such as Crohn’s disease and rheumatoid arthritis. A number of serious adverse drug reactions are known to be associated with IFX use; they include infections, malignancies, and injection site reactions. Although a few case reports have described potential psychiatric adverse events (including suicide attempts and manic episodes), the latter are barely mentioned in IFX’s summary of product characteristics. The objective of the present retrospective study was to detect potential psychiatric adverse events associated with IFX treatment by analyzing a national discharge abstract database.

Materials and Methods

We performed an historical cohort study by analyzing data from the French national hospital discharge abstract database (PMSI) between 2008 and 2014. All patients admitted with one of the five diseases treated with IFX were included.

Results

Of the 325,319 patients included in the study, 7,600 had been treated with IFX. The proportion of hospital admissions for one or more psychiatric events was higher among IFX-exposed patients (750 out of 7,600; 9.87%) than among non-exposed patients (17,456 out of 317,719; 5.49%). After taking account of potential confounders in the cohort as a whole, a semi-parametric Cox regression analysis gave an overall hazard ratio (HR) [95% confidence interval] (CI) of 4.5 [3.95; 5.13] for a hospital admission with a psychiatric adverse event during treatment with IFX. The HR (95%CI) for a depressive disorder was 4.97 (7.35; 6.68). Even higher risks were observed for certain pairs of adverse events and underlying pathologies: psychotic disorders in patients treated for ulcerative colitis (HR = 5.43 [2.01; 14.6]), manic episodes in patients treated for severe psoriasis (HR = 12.6 [4.65; 34.2]), and suicide attempts in patients treated for rheumatoid arthritis (HR = 4.45 [1.11; 17.9]).

Discussion

The present retrospective, observational study confirmed that IFX treatment is associated with an elevated risk of psychiatric adverse events. Depending on the disease treated, physicians should be aware of these potential adverse events.

Role of atmospheric pollution on the natural history of idiopathic pulmonary fibrosis

INTRODUCTION

Idiopathic pulmonary fibrosis (IPF) has an unpredictable course corresponding to various profiles: stability, physiological disease progression and rapid decline. A minority of patients experience acute exacerbations (AEs). A recent study suggested that ozone and nitrogen dioxide might contribute to the occurrence of AE. We hypothesised that outdoor air pollution might influence the natural history of IPF.

METHODS

Patients were selected from the French cohort COhorte FIbrose (COFI), a national multicentre longitudinal prospective cohort of IPF (n=192). Air pollutant levels were assigned to each patient from the air quality monitoring station closest to the patient's geocoded residence. Cox proportional hazards model was used to evaluate the impact of air pollution on AE, disease progression and death.

RESULTS

Onset of AEs was significantly associated with an increased mean level of ozone in the six preceding weeks, with an HR of 1.47 (95% CI 1.13 to 1.92) per 10 µg/m³ (p=0.005). Cumulative levels of exposure to particulate matter PM₁₀ and PM_2.5 were above WHO recommendations in 34% and 100% of patients, respectively. Mortality was significantly associated with increased levels of exposure to PM₁₀ (HR=2.01, 95% CI 1.07 to 3.77) per 10 µg/m³ (p=0.03), and PM_2.5 (HR=7.93, 95% CI 2.93 to 21.33) per 10 µg/m³ (p<0.001).

CONCLUSION

This study suggests that air pollution has a negative impact on IPF outcomes, corroborating the role of ozone on AEs and establishing, for the first time, the potential role of long-term exposure to PM₁₀ and PM_2.5 on overall mortality.

Characteristics and consequences of medical care interruptions in HIV-infected patients in France

To describe the consequences of medical care interruptions (MCIs) we selected patients with at least two medical encounters between January 2006 and June 2013 in the Dat'AIDS cohort. Patients with any time interval >15 months between two visits were defined as having a MCI, as opposed to uninterrupted follow-up (UFU). Patients' characteristics at the time of HIV diagnosis and at the censoring date were compared between groups. Cox proportional hazards models were built to assess the role of interruptions on survival (total and AIDS-free). Of 11 116 patients, 824 had at least one MCI. These patients were younger at the time of HIV diagnosis (30 vs. 33 years, P < 0·0001). MCI was less frequent in men having sex with men vs. heterosexual patients [odds ratio (OR) 0·81, 95% confidence interval (CI) 0·69-0·96)], and a centre effect was described. MCI was independently associated with AIDS (OR 2·54, 95% CI 2·10-3·09) and death (OR 2·65, 95% CI 1·94-3·61). At the censoring date, 52·2% of patients with at least one MCI had viral load below detection vs. 85·3% of the UFU group (P < 0·0001). In conclusion, MCIs were associated with patients' survival and with the proportion of viral loads below detection in our cohort, compromising individual and collective treatment benefits.

Incidence and remission of urinary incontinence at midlife: a cohort study

OBJECTIVE

Urinary incontinence (UI) is often considered to be an age-related disease that develops gradually as women grow older. Much remains to be learnt about factors that promote its incidence or its remission. Our objective was to assess its incidence and risk factors.

DESIGN

Longitudinal cohort study.

SETTING

French GAZEL cohort.

POPULATION

A cohort of 4127 middle-aged women (aged 47-52 years at baseline) over an 18-year period (1990-2008).

METHODS

UI was defined as 'difficulty retaining urine'. The question was asked at baseline and repeated every 3 years over an 18-year period. Two groups (UI incidence and remission) were analysed according to status at baseline (continent or incontinent). A multivariable analysis (Cox model) was used to estimate the risk factors for UI incidence and remission.

MAIN OUTCOME MEASURES

Annual incidence and remission rates and risk factors for UI incidence and remission.

RESULTS

The annual incidence and remission rates for UI were 3.3% and 6.2%, respectively. High educational level (hazard ratio [HR] = 1.28; 95% confidence interval [95% CI] = 1.05-1.55), parity, i.e. at least one baby versus no baby (HR = 1.64; 95% CI = 1.19-2.27), menopause (HR = 5.44; 95% CI = 4.47-6.63), weight gain, i.e. for each kilogram change in weight (HR = 1.00; 95% CI = 1.00-1.02), onset of depressive symptoms (HR = 1.31; 95% CI = 1.09-1.57) and impairment in health-related quality of life incidence (social isolation dimension [HR = 1.29; 95% CI = 1.04-1.60] and energy dimension [HR = 1.41; 95% CI = 1.17-1.70]) were associated with an increased probability of UI. The factors associated with persistent UI were age (HR = 0.58; 95% CI = 0.55-0.61), weight gain (HR = 0.99; 95% CI = 0.98-0.99) and transition to menopausal status (HR = 1.54; 95% CI = 1.19-1.99).

CONCLUSIONS

Our study suggests that, in our population of middle-aged women, age, menopause, weight gain, onset of depression and impaired health-related quality of life may promote UI.

Predictors of decline in walking ability in community-dwelling Alzheimer's disease patients: Results from the 4-years prospective REAL.FR study

Introduction

The aim of this study was to explore the predictors of decline in walking ability in patients with Alzheimer’s disease (AD).

Methods

The prospective REseau surla maladie ALzheimer FRançais (REAL.FR) study enrolled six hundred eighty four community-dwelling AD subjects (71.20% women; mean age 77.84 Standard Deviation, SD, 6.82 years, Mini-Mental State Examination 20.02, SD 4.23). Decline in walking ability was defined as the first loss of 0.5 points or more in the walking ability item of the Activities of Daily Living scale (ADL), where higher score means greater independence, during the four-years of follow-up. Demographic characteristics, co-morbidities, and level of education were reported at baseline. Disability, caregiver burden, cognitive and nutritional status, body mass index, balance, behavioral and psychological symptoms of dementia, medication, hospitalization, institutionalization and death were reported every six months during the four years. Cox survival analyses were performed to assess the independent factors associated with decline in walking ability.

Results

The mean incident decline in walking ability was 12.76% per year (95% Confidence Interval (CI) 10.86 to 14.66). After adjustment for confounders, the risk of decline in walking ability was independently associated with older age (Relative Risk, RR = 1.05 (95% CI 1.02 to 1.08)), time from diagnosis of dementia (RR = 1.16 (1.01 to 1.33)), painful osteoarthritis (RR = 1.84 (1.19 to 2.85)), hospitalization for fracture of the lower limb (RR = 6.35 (3.02 to 13.37)), higher baseline ADL score (RR = 0.49 (0.43 to 0.56)), and the use of acetylcholinesterase inhibitors (RR = 0.52 (0.28 to 0.96)).

Conclusions

The risk of decline in walking ability is predicted by older age, increased dementia severity, poor functional score, and orthopedic factors and seems to be prevented by the use of acetylcholinesterase inhibitors medication.

First malaria infections in a cohort of infants in Benin: biological, environmental and genetic determinants. Description of the study site, population methods and preliminary results

OBJECTIVES

Malaria infection of the placenta during pregnancy was found to be associated with infant susceptibility to malaria. Other factors such as the intensity of malaria transmission and the nutritional status of the child might also play a role, which has not been adequately taken into account in previous studies. The aim of this study was to assess precisely the parts played by environmental, nutritional and biological determinants in first malaria infections, with a special interest in the role of placental infection. The objective of this paper is not to present final results but to outline the rationale of the study, to describe the methods used and to report baseline data.

DESIGN

A cohort of infants followed with a parasitological (symptomatic and asymptomatic parasitaemia) and nutritional follow-up from birth to 18 months. Ecological, entomological and behavioural data were collected along the duration of the study.

SETTING

A rural area in Benin with two seasonal peaks in malaria transmission.

PARTICIPANTS

656 infants of women willing to participate in the study, giving birth in one of the three maternity clinics and living in one of the nine villages of the study area.

PRIMARY OUTCOME MEASURES

The time and frequency of first malaria parasitaemias in infants, according to Plasmodium falciparum infection of the placenta.

RESULTS

11% of mothers had a malaria-infected placenta at delivery. Mosquito catches made every 6 weeks in the area showed an average annual P falciparum entomological inoculation rate of 15.5, with important time and space variations depending on villages. Similarly, the distribution of rainfalls, maximal during the two rainy seasons, was heterogeneous over the area.

CONCLUSIONS

Considering the multidisciplinary approach of all factors potentially influencing the malaria status of newborn babies, this study should bring evidence on the implication of placental malaria in the occurrence of first malaria infections in infants.