Unadjusted Incidence Rate Research Articles

Smoking and predictors of pneumonia among HIV-infected patients receiving care in the HAART era.

Background: Smoking tobacco is disproportionably common among HIV-infected patients in the highly active antiretroviral therapy (HAART) era. Methods: An observational cohort study of 300 HIV-positive patients receiving care between 1996 and 2005 examined the effect of smoking on pneumonia risk. Multivariable analyses assessed the association between smoking and pneumonia risk and identified independent predictors of pneumonia during the HAART era. Results: Current smoking was common (67%). Eighty-two patients (27%) experienced 119 pneumonia episodes during 2151 patient-years of follow-up, with 7.2 episodes/100 person-years among smokers and 2.9 episodes/100 person-years among non-smokers (unadjusted incidence rate ratio (IRR): 2.50 (95% CI: 1.58, 4.09). Adjustment for age and HIV RNA level resulted in an IRR of 1.77 (95% CI: 0.98, 3.21). No prior antiretroviral therapy use (P-value <0.001), higher HIV RNA level (P-value = 0.01), lower CD4 count (P-value = 0.01), younger age (P-value = 0.01), and alcohol use (P-value = 0.04) were independent predictors of pneumonia. HAART use decreased pneumonia risk (IRR 0.28, 95% CI: 0.18, 0.44). Conclusions: While HIV-positive smokers had over a 2-fold increase in the rate of pneumonia, the trend did not reach statistical significance in multivariable models. Clinical factors such as HAART, alcohol use and immunological status are important in pneumonia risk.

Hospital Admissions Associated with Traumatic Brain Injury in the US Army during Peacetime: 1990s Trends

Introduction: This paper examines 10-year trends in traumatic brain injury (TBI)-related hospitalization rates for active duty US Army personnel in the 1990s. It does this within the context of various factors, including enhanced injury prevention policies and changed hospital admission practices, that may have affected TBI hospitalization rates. It also compares TBI hospitalization rates in the Army to those from an age-comparable segment of the US civilian population over this time period. Methods: Crude (unadjusted) incidence rates for all active duty US Army personnel hospitalized with a TBI diagnosis from fiscal years (FY) 1990 to 1999 were calculated. Once the trends were identified, the percentage change in the overall rate, as well as the rates for different TBI severity levels, and in-hospital deaths from FY1990 and FY1999 were analyzed. Changes in age- and gender-specific rates as well as crude rates for cases with and without other injuries and cases treated in military and civilian hospitals were also analyzed. Rate ratios were used to compare aggregated 5-year TBI hospitalization rates in the Army to rates for civilians 17–49 years of age during the following time periods: 1990–1994 and 1995–1999. The rates used in the comparison were adjusted to control for differences in age and gender. Results: The overall incidence of TBI-related hospitalization in the Army decreased 75% from FY1990 to FY1999. The rates for all TBI severity levels decreased, but the rate for mild TBI decreased more than the rates for moderate and severe TBI. The rate of in-hospital deaths from TBI also decreased. Rates decreased similarly for males and females, across all age groups, as well as for cases with and without other injuries. TBI rates decreased for Army personnel treated in military hospitals but changed minimally for Army personnel treated in civilian hospitals. The Army’s TBI hospitalization rates were generally higher than civilian rates in the early 1990s but by the late 1990s, most of the Army’s rates were lower than or equal to the civilian rates. Conclusions: The incidence of TBI-related hospitalization in the active duty US Army decreased markedly (75%) during the 1990s. As a result, most of the Army’s TBI hospitalization rates were lower than civilian rates by the late 1990s. Effective injury prevention and changes in the Army population were two of the factors that likely contributed to the decrease in rates for all TBI severity levels, while changes in hospital admission practices likely contributed to the disproportionate decrease in the Army’s rates for mild TBI.

Racial and gender differences in susceptibility to tobacco smoke among patients with chronic obstructive pulmonary disease: Respir Med 2005; published online ahead of print on 15 October 2005 as doi:10.1016/j.rmed.2005.09.019

Immunosuppressive therapy for inflammatory bowel disease (IBD) in pediatric patients is thought to increase the risk of malignancy and lymphoproliferative disorders, including hemophagocytic lymphohistiocytosis (HLH). We compared unadjusted incidence rates of malignancy and HLH in pediatric patients with IBD exposed to infliximab (IFX) with patients not exposed to biologics and calculated standardized incidence ratios (SIRs).We collected and analyzed data from 5766 participants in a prospective study of long-term outcomes of pediatric patients with IBD (NCT00606346), from May 31, 2007 through June 30, 2016. Patients were 17 years old or younger and had Crohn’s disease, ulcerative colitis, or IBD-unclassified with 24,543.0 patient-years of follow-up. We estimated incidence rates for malignancy and HLH as events/1000 patient-years of follow-up. We calculated age-, sex-, and race-adjusted SIRs, with 95% confidence intervals (CIs), using the Surveillance, Epidemiology, and End Results Program (SEER) database.Thirteen of the 15 patients who developed a malignancy and all 5 of the patients who developed HLH had been exposed to thiopurines; 10 patients with malignancy had also been exposed to a biologic agent. Unadjusted incidence rates showed no increased risk of malignancy (0.46/1000 patient-years) or HLH (0.0/1000 patient-years) in patients exposed to IFX as the only biologic vs those unexposed to biologics (malignancy: 1.12/1000 patient-years; HLH: 0.56/1000 patient-years). SIRs did not demonstrate an increased risk of malignancy among patients exposed to IFX (SIR, 1.69; 95% CI, 0.46–4.32) vs patients not exposed to a biologic agent (SIR, 2.17; 95% CI, 0.59–5.56), even when patients were stratified by thiopurine exposure.In determination of age-, sex-, and race-adjusted SIRs using data from a large clinical study and the SEER database, we found that IFX exposure did not associate with increased risk of malignancy or HLH in pediatric patients with IBD. Thiopurine exposure is an important precedent event for the development of malignancy or HLH in pediatric patients with IBD.

Injury history as a risk factor for incident injury in youth soccer

Objectives: To determine if athletes with a self reported history of previous injury have a higher incident injury rate than athletes without a self reported injury history. Methods: A prospective...

Incidence of Cryptosporidium parvum in the dairy cattle population in a New York City Watershed

A longitudinal study of 2-year duration was conducted to determine the risk, as measured by incidence rate, of Cryptosporidium parvum infection among dairy cattle in the Catskill/Delaware Watershed of New York City (NYC), and the factors that predispose animals to the likelihood of infection. A proportional sampling scheme with follow up at quarterly farm visits was employed for heifers and cows. Additionally, all calves born on the 39 study farms were sampled once during the first four weeks of life and at least once more before weaning. Samples were analyzed for the presence of C. parvum using a quantitative centrifugation concentration flotation technique and a C. parvum-specific enzyme-linked immunosorbent assay (ELISA). Of the 9914 fecal samples collected, 747 were found to contain C. parvum. The average number of oocysts detected was 1.3 × 10 5/g (range: 1.0/g–8.2 × 10 6/g). The average age at time of first detection of the organism was 15.0 days with a standard deviation of 6.59 days. The age range of animals infected with C. parvum in the study population was 3–60 days (inclusive). The unadjusted (crude) incidence rate of C. parvum among the entire study population was 2.05 per 1000 animal-days. The unadjusted incidence rate among pre-weaned calves was 15.55 per 1000 animal-days. After controlling for age and prior protozoal risk level, no seasonal impact on the incidence of C. parvum was detected among animals less than 61 days by negative binomial regression. A seasonal impact was identified among the oocyst counts of infected animals after controlling for age and prior protozoal risk level.

Racial variations in location and risk of intracerebral hemorrhage.

Risk factors for intracerebral hemorrhage (ICH) vary by location. Incidence rates of ICH are known to be higher in American blacks than whites, but how rates may differ by hemorrhage location is unknown. We sought to define incidence rates for different ICH locations in a biracial population. All hospitalized patients age > or =20 years with spontaneous ICH were identified in the Greater Cincinnati/Northern Kentucky metropolitan area from May 1998 to July 2001 and August 2002 to April 2003. Incidence rates per 100,000 persons were age, sex, and race adjusted as appropriate to the 2000 US population. Risk ratios (RRs) with 95% CIs were calculated from unadjusted incidence rates. There were 1038 qualifying ICHs. Annual incidence rates per 100,000 persons > or =20 years of age were 48.9 for blacks and 26.6 for whites. Annual incidence rates per 100,000 blacks in lobar, deep cerebral, brain stem, and cerebellar locations were 15.2, 25.7, 5.1, and 2.9, respectively. Annual incidence rates per 100,000 whites in the same locations were 9.4, 13.0, 1.3, and 2.9. The greatest excess risk of ICH in blacks compared with whites was found among young to middle-aged (35 to 54 years) persons with brain stem (RR, 9.8; 95% CI, 4.2 to 23.0) and deep cerebral (RR, 4.5; 3.0 to 6.8) hemorrhage. The excess risk of ICH in American blacks is largely attributable to higher hemorrhage rates in young and middle-aged persons, particularly for deep cerebral and brain stem locations. Hypertension is the predominant risk factor for hemorrhages in these locations.

The Effect of HIV Coinfection on the Risk of Cirrhosis and Hepatocellular Carcinoma in U.S. Veterans with Hepatitis C

This study was conducted to determine whether HIV coinfection increases the risk of cirrhosis in HCV-infected patients in the HAART and pre-HAART eras. Further, the risk of hepatocellular carcinoma was also examined. This retrospective cohort study was conducted among HCV-infected veterans who were seen at one of the 172 Veterans Health Administration hospitals between October 1, 1991 and September 30, 2000. Patients with prerecorded advanced liver disease were excluded. Incidence rates, cumulative incidence, and Cox proportional hazard ratios were calculated. There were 26,641 patients with HCV-only and 4,761 patients with HCV-HIV coinfection. The unadjusted incidence rate of cirrhosis was lower in patients with coinfection than HCV-only (p < 0.01). After controlling for demographics and confounders (including alcoholism and chronic hepatitis B), coinfection was not significantly associated with cirrhosis. However, there was an increased risk of cirrhosis in patients with coinfection compared to HCV-only during the pre-HAART era (before October 1, 1996) (hazard ratio = 1.48, 1.06-2.07, p= 0.02), but not among patients who entered the cohort during the HAART era. The unadjusted incidence rate of hepatocellular carcinoma in patients with coinfection and HCV-only was 1.3 and 2/1,000 person-years, respectively (p= 0.04). In the multivariate model, coinfection was not associated with hepatocellular carcinoma (hazard ratio = 0.84, p= 0.40). Coinfection was a significant risk factor for cirrhosis only during the pre-HAART era and was not associated with hepatocellular carcinoma, irrespective of time period.

Regional variation in incidence of primary total hip arthroplasties and revisions in Denmark, 1996–2002

Background We examined incidence rates (IR) of total hip arthroplasty (THA) in Denmark according to county and type of hospital, and investigated possible factors associated with any variations.Methods Through the Danish Hip Arthroplasty Registry, we identified all cases of primary THAs (n = 37,144) and revisions (n = 6,446) between 1996 and 2002. Unadjusted and age- and gender-standardized, hospital type- and county-specific IRs were calculated. Using multiple regression analysis, we examined possible factors associated with the variations.Results Over the study period, age- and sex-standardized IRs of primary THAs for university and other hospitals increased by 10% and 40%, respectively. IRs of revisions increased for other hospitals by 33%, but decreased for university hospitals by 30%. Unadjusted IRs varied among counties (n = 15), which remained despite age- and gender-standardization. The IR ratio was 1.4 (95% CI: 1.3–1.6) when comparing the counties with the highest and lowest IRs. No association was found between IRs of THA and the number of orthopedic surgeons per 100,000 inhabitants, proportion of patients with primary arthrosis, preoperative Harris Hip Score, hospital costs, the counties’Gross Domestic Product, or population density.Interpretation Substantial regional differences in the IRs of THA procedures were found. We found no associations between IRs and a range of patient- and healthcare system-related factors. ▪

Influence of site classification on cancer incidence rates: an analysis of gastric cardia carcinomas.

Recent reports suggest that the incidences of cardia and gastroesophageal junction carcinomas have increased markedly. The influence of improvements in cancer site classification (i.e., from no specific site to a specific site) on these incidence rates is unknown. We analyzed data for all gastric cancers reported to the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) cancer registries from 1974 through 1998. We compared incidence figures adjusted for improvements in site classification with the standard unadjusted incidence rates traditionally reported from SEER data. All analyses used two-sided statistical tests. Among white males, the proportion of gastric cancers with an unspecified location decreased from 38% from 1974 to 1976 to 14% in 1996 to 1998. Between 1974-1976 and 1996-1998, the adjusted cardia cancer incidence rate for white males was unchanged (5.3% increase, from 3.6 to 3.8 per 100,000 population/year, respectively; P =.59), whereas the unadjusted cardia cancer incidence rate underwent a statistically significant increase (77% increase, from 1.9 to 3.4 per 100 000 population/year, respectively; P<.001). During the same period, the adjusted noncardia gastric cancer incidence rate in white males decreased from 6.8 to 3.8 per 100,000 population/year (P<.001), an absolute decrease more than twice as large as that seen using standard unadjusted SEER data (from 4.5 to 3.2 per 100,000 population/year; P<.001). Similar findings were observed for black males. Improved specification of gastric cancer sites may largely account for the purported increase in cardia cancer incidence in recent decades. Noncardia gastric cancer incidence may be decreasing much more rapidly than previously appreciated. These results illustrate the potentially large influence of changes in site classification on some cancer incidence rates.

Exposure misclassification as a result of free sample drug utilization in automated claims databases and its effect on a pharmacoepidemiology study of selective COX-2 inhibitors.

Free drug samples are widely used in clinical practice. We were concerned about free sample drug utilization as a source of misclassification in pharmacoepidemiology research using claims data that may result in biased effect estimates. We investigated the magnitude of potential bias with sensitivity analyses based on a published study that examined cardiovascular risk associated with selective cyclooxygenase 2 (COX-2) inhibitors. We derived an estimate of free sample drug utilization with market data for rofexcoxib and calculated sensitivity of the exposure ascertainment method using claims data. We corrected the incidence rate ratio assuming the observed unexposed incidence rate was actually a weighted average rate of the truly unexposed and free sample drug users. The impact of exposure misclassification measured as the percentage change from a corrected to the reported crude incidence rate ratio was examined under a range of free sample drug utilization proportions and unexposed cohort sizes. The proportion of free sample drug utilization of all rofecoxib use in our base case scenario was 15.48%, resulting in sensitivity of 84.52% for exposure ascertainment. The magnitude of bias was an underestimation of the unadjusted incidence rate ratio by 0.03%. With a free sample drug utilization proportion of 1.48% and the same unexposed cohort size of 237 975 person-years, the underestimation was 0.003%. If the unexposed cohort were 975 person-years given a 15.48% proportion, the underestimation was 8.82%. In the pharmacoepidemiology study, we examined that uses claims data to ascertain drug exposure, our results suggest that adjustment for free sample drug utilization is probably not warranted.

Impact of Reporting Delay and Reporting Error on Cancer Incidence Rates and Trends

Cancer incidence rates and trends are a measure of the cancer burden in the general population. We studied the impact of reporting delay and reporting error on incidence rates and trends for cancers of the female breast, colorectal, lung/bronchus, prostate, and melanoma. Based on statistical models, we obtained reporting-adjusted (i.e., adjusted for both reporting delay and reporting error) case counts for each diagnosis year beginning in 1981 using reporting information for patients diagnosed with cancer in 1981-1998 from nine cancer registries that participate in the Surveillance, Epidemiology, and End Results (SEER) program. Joinpoint linear regression was used for trend analysis. All statistical tests are two-sided. Initial incidence case counts (i.e., after the standard 2-year delay) accounted for only 88%-97% of the estimated final counts; it would take 4-17 years for 99% or more of the cancer cases to be reported. The percent change between reporting-adjusted and unadjusted cancer incidence rates for the 1998 diagnosis year ranged from 3% for colorectal cancers to 14% for melanoma in whites and for prostate cancer in black males. Reporting-adjusted current incidence trends for breast cancer and lung/bronchus cancer in white females showed statistically significant increases (estimated annual percent change [EAPC] = 0.6%, 95% confidence interval [CI] = 0.1% to 1.2%) and 1.2%, 95% CI = 0.7% to 1.6%, respectively), whereas trends for these cancers using unadjusted incidence rates were not statistically significantly different from zero (EAPC = 0.4%, 95% CI = -0.1% to 0.9% and 0.5%, 95% CI = -0.1% to 1.1%, respectively). Reporting-adjusted melanoma incidence rates for white males showed a statistically significant increase since 1981 (EAPC = 4.1%, 95% CI = 3.8% to 4.4%) in contrast to the unadjusted incidence rate, which was most consistent with a flat or downward trend (EAPC = -4.2%, 95% CI = -11.1% to 3.3%) after 1996. Reporting-adjusted cancer incidence rates are valuable in precisely determining current cancer incidence rates and trends and in monitoring the timeliness of data collection. Ignoring reporting delay and reporting error may produce downwardly biased cancer incidence trends, particularly in the most recent diagnosis years.

Morbidity and mortality in South African gold miners: impact of untreated disease due to human immunodeficiency virus.

A cohort of 1792 human immunodeficiency virus (HIV)-positive and 2970 HIV-negative South African miners was observed for 12 months starting in February 1998. All-cause hospitalizations and deaths were significantly associated with HIV infection (respective unadjusted incidence rate ratios, 2.9 and 9.2; respective 95% confidence intervals, 2.5-3.4 and 5.5-16.0). Tuberculosis (TB), bacterial pneumonia, cryptococcosis, and trauma were the major causes of admission for HIV-positive patients, whereas Pneumocystis carinii pneumonia was an uncommon cause (respective admission rates, 8.5, 6.9, 2.2, 6.0, and 0.53 admissions per 100 person-years). Enteritis, bronchitis, urinary tract infections, and soft-tissue infections were also significantly associated with HIV infection. Cryptococcosis caused 44% of deaths among HIV-positive patients. Trauma was the main hazard for HIV-negative men, causing 42% of admissions and 60% of deaths. A broad range of infectious conditions is significantly associated with HIV infection in South African miners. Identification and implementation of effective prophylactic regimens are urgently needed.

Contraception and the risk of type 2 diabetes mellitus in Latina women with prior gestational diabetes mellitus.

Effective contraception is essential in women with prior gestational diabetes mellitus (GDM) but should not increase their already substantial risk of developing type 2 diabetes. To determine whether exposure to low-dose oral contraceptives increases the risk of developing type 2 diabetes mellitus in women with recent GDM. Retrospective cohort study of 904 Latinas with GDM who gave birth between January 1987 and March 1994, in whom postpartum diabetes was excluded at 4 to 16 weeks post partum. At their initial postpartum visit, 443 women selected a nonhormonal form of contraception, 383 received a low-dose, estrogen-progestin combination oral contraceptive (OC), and 78 breast-feeding women received the progestin-only OC. When breast-feeding ended, patients initially taking progestin-only OCs were switched to combination OCs. Patients were followed up periodically with oral glucose tolerance tests for up to 7 1/2 years. Person time was used to compute unadjusted average annual incidence rates of developing diabetes mellitus, as defined by the National Diabetes Data Group Criteria. Survival analysis was used to compute the unadjusted cumulative incidence rates and adjusted relative risks of diabetes mellitus. The unadjusted average annual incidence rates of type 2 diabetes mellitus were 8.7%, 10.4%, and 26.5%, respectively, for patients using nonhormonal forms of contraception, combination OCs, and progestin-only OCs. Cumulative incidence rates were virtually identical for patients with uninterrupted use of combination OCs and nonhormonal forms of contraception, but patients using progestin-only OCs developed diabetes mellitus more rapidly during the first 2 years of use. After adjustment for potential confounding factors, the use of progestin-only OCs almost tripled the risk of type 2 diabetes mellitus compared with equivalent use of low-dose combination OCs (adjusted relative risk, 2.87; 95% confidence interval, 1.57-5.27). The magnitude of this risk increased with duration of uninterrupted use. Progestin-only OCs were associated with an increased risk of diabetes in breast-feeding Latinas with recent GDM and probably should be prescribed with caution, if at all, in these women. Long-term use of low-dose combination OCs did not increase the risk of type 2 diabetes compared with use of nonhormonal contraception. Thus, combination OCs do not appear to increase the risk of diabetes in non-breast-feeding women with recent GDM.

The effect of education on the incidence of dementia and Alzheimer's disease in the Framingham Study

To evaluate whether low educational attainment is a risk factor for the incidence of dementia and Alzheimer's disease (AD) in the Framingham Study and to determine whether age at onset of dementia is earlier in persons with low educational levels. A community-based cohort was studied longitudinally for the development of dementia. Diagnosis was made according to strict criteria by two neurologists and a neuropsychologist. Subtype of dementia and year at onset were determined. Incidence rates were compared in three education groups: < grade school, < high school, and > or = high school. A total of 3,330 men and women aged 55 to 88 years. During 17 years of follow-up, 258 incident cases of dementia, including 149 AD cases, were identified. Unadjusted incidence rates were significantly elevated (p < 0.05) for dementia and non-AD dementia among the least educated. The age-adjusted relative risk for subjects with a grade school education or less compared with those who earned a high school diploma was 1.31 (95% confidence interval [CI], 0.90 to 1.90) for dementia generally, 1.04 (95% CI, 0.62 to 1.74) for AD, and 1.75 (95% CI, 1.03 to 2.98) for non-AD dementia. Age at onset of dementia did not vary by educational attainment. After age adjustment, low educational attainment was not a significant risk factor for the incidence of dementia generally or of AD. Low educational attainment was associated with increased risk of non-AD dementia, perhaps because of deleterious smoking habits and other risk factors for stroke in the least-educated individuals. Adequately adjusting for age and examining subtypes of dementia are important in assessing the influence of education on dementia incidence.

Selection of the Optimal Skeletal Site for Fracture Risk Prediction

Commonly known risk factors have been shown to correlate with mean bone mass in populations, but none of these risk factors, either alone or in combination, have been shown to be predictive of future fracture risk in an individual. In order to evaluate the predictive power of bone mineral measurements at various sites, bone mineral content (BMC) has been measured at four skeletal sites and compared to subsequent fracture incidence at all skeletal locations, including spine and appendicular sites. Os calcis BMC has the most consistent monotonic relationship to unadjusted fracture incidence rates; os calcis BMC also has the strongest (p = 0.009) relation to levels of relative risk, after adjustment for age, height, and weight. Based on actual ability to predict fracture risk prospectively, along with such secondary criteria as cost, ease of performance, precision, and radiation exposure, the os calcis appears to be an optimal BMC measurement site for routine screening of perimenopausal women.