Calendar Time Period Research Articles

A Cohort Study of Breast Cancer Risk in Breast Reduction Patients

Surgical reduction of the female breast (reduction mammaplasty) is very common in plastic surgery. The purpose of this study was to determine whether women who have undergone breast reduction surgery are at the same, greater, or lesser risk of developing breast cancer than women who have not undergone breast reduction surgery. This study incorporates a population-based, nonconcurrent cohort linkage methodology. The Canadian Institute for Health Information hospital records were used to identify all Ontario women who had undergone breast reduction surgery in Ontario between 1979 and 1992. Three computerized probabilistic record linkages were performed. The first linkage was between a file of the 28,042 Ontario women who had undergone bilateral breast reduction surgery between April 1, 1979, and December 31, 1992, and a file of incident cancer cases among Ontario women for the calendar period 1979 to 1993. Follow-up of the cohort was undertaken starting from the date of breast reduction surgery, and vital status was ascertained as of December 31, 1993, by record linkage with the Ontario Mortality Database maintained at the Ontario Cancer Registry. The incidence of cancer in the Ontario breast reduction cohort was compared with the cancer incidence of the general Ontario population after appropriate adjustments for age and calendar time period. The expected number of cancers was calculated using the “PERSON YEARS” computer program. Within the cohort, followed for an average of 6.5 years after bilateral breast reduction surgery, 101 breast cancers were observed and 165.8 were expected, for a standardized incidence ratio of 0.61 (0.50 to 0.74, 95 percent confidence interval). This effect was independent of patient age at breast reduction. This study demonstrates that there is no increased risk of breast cancer after bilateral breast reduction surgery and, in fact, a significant decreased risk existed in women followed for an average of 6.5 years. (Plast. Reconstr. Surg. 103: 1674, 1999.)

A cohort study of breast cancer risk in breast reduction patients.

Surgical reduction of the female breast (reduction mammaplasty) is very common in plastic surgery. The purpose of this study was to determine whether women who have undergone breast reduction surgery are at the same, greater, or lesser risk of developing breast cancer than women who have not undergone breast reduction surgery. This study incorporates a population-based, non-concurrent cohort linkage methodology. The Canadian Institute for Health Information hospital records were used to identify all Ontario women who had undergone breast reduction surgery in Ontario between 1979 and 1992. Three computerized probabilistic record linkages were performed. The first linkage was between a file of the 28,042 Ontario women who had undergone bilateral breast reduction surgery between April 1, 1979, and December 31, 1992, and a file of incident cancer cases among Ontario women for the calendar period 1979 to 1993. Follow-up of the cohort was undertaken starting from the date of breast reduction surgery, and vital status was ascertained as of December 31, 1993, by record linkage with the Ontario Mortality Database maintained at the Ontario Cancer Registry. The incidence of cancer in the Ontario breast reduction cohort was compared with the cancer incidence of the general Ontario population after appropriate adjustments for age and calendar time period. The expected number of cancers was calculated using the "PERSON YEARS" computer program. Within the cohort, followed for an average of 6.5 years after bilateral breast reduction surgery, 101 breast cancers were observed and 165.8 were expected, for a standardized incidence ratio of 0.61 (0.50 to 0.74, 95 percent confidence interval). This effect was independent of patient age at breast reduction. This study demonstrates that there is no increased risk of breast cancer after bilateral breast reduction surgery and, in fact, a significant decreased risk existed in women followed for an average of 6.5 years.

Pre-AIDS mortality from natural causes associated with HIV disease progression: evidence from the European Seroconverter Study among injecting drug users.

To study differences in pre-AIDS mortality between European cohorts of injecting drug users (IDU) and to evaluate whether pre-AIDS mortality increased with time since HIV seroconversion and decreasing CD4 count. The study population consisted of 664 IDU with documented intervals of HIV seroconversion from eight cohort studies. Differences in pre-AIDS mortality were studied between European sites; an evaluation of whether pre-AIDS mortality increased with time since HIV seroconversion and decreasing CD4 count was carried out using Poisson regression. One hundred and seven IDU died, of whom 57 did not have AIDS. Pre-AIDS causes of death were overdose/suicide (49%), natural causes such as bacterial infections/cirrhosis (40%), and unintentional injuries/unknown (11%). Considering pre-AIDS death and AIDS as competing risks, 14.7% were expected to have died without AIDS and 17.3% to have developed AIDS at 7 years from seroconversion. No statistically significant differences in pre-AIDS mortality were found between European regions, men and women, age categories and calendar time periods. Overall pre-AIDS mortality did not increase with time since seroconversion, but did increase with decreasing CD4 count. Evaluating cause-specific mortality, only pre-AIDS mortality from natural causes appeared to be associated with time since seroconversion as well as immunosuppression. For natural causes, the death rate per 100 person-years was 0.13 the first 2 years after seroconversion, 0.73 in years 2-4 [risk relative (RR) to years 0-2, 5.6], 1.83 in years 4-6 (RR, 14.0) and 1.54 for > or = 6 years (RR, 11.7). This rate was 0 for a CD4 cell count > or = 500 x 10(6)/l, 1.06 for 200-500 x 10(6)/l and 4.06 for < 200 x 10(6)/l (RR versus > or = 200 x 10(6)/l, 7.0). In multivariate analysis, both CD4 count and time since seroconversion appeared to be independently associated with death from natural causes; CD4 count appeared to be the strongest predictor (adjusted RR, 5.9). A high pre-AIDS mortality rate was observed among IDU. No significant differences were observed across European sites. Pre-AIDS mortality from natural causes but not from overdose and suicide was associated with HIV disease progression.

Kaposi's sarcoma and non-Hodgkin's lymphoma following the diagnosis of AIDS. Multistate AIDS/Cancer Match Study Group.

We linked records of 83,434 AIDS cases reported to AIDS registries through 1990 to cancer registry records during times when overlap in registration existed. Of 8,496 Kaposi's-sarcoma (KS) cases meeting enrollment criteria, 1,045 occurred semesters 2 through 4 (6 through 23 months) after another AIDS-defining illness. KS risk in this period after AIDS declined steadily over the 1980s. Adjusting for age, gender, ethnic origin and calendar time period, we found the relative risk (RR) of KS to be 106,000 for homo/bisexual men with AIDS and 13,000 for other men with AIDS. Risk was highest for homo/bisexual men between 30 and 39 years old and among 20- to 29-year-old non-homo/bisexual men. The RR in black men was approximately half that reported in white men among homo-bisexual men and others. Between the second and fourth semester after AIDS, the ratio of RR of KS to that of non-AIDS-related cancers increased 1.5-fold. In a similar analysis, there were 335 non-Hodgkin's lymphoma (NHL) cases in semesters 2 through 4 after AIDS. The overall risk was elevated 283-fold in homo/bisexual men and the RR ratio increased 1.8-fold between semester 2 and 4 after AIDS. In summary, the risk of KS following another AIDS-defining illness is strikingly high, more in white men than in black men, and the risks of KS and, especially, NHL appear to increase with time from AIDS.

Kaposi's sarcoma and non‐Hodgkin's lymphoma following the diagnosis of AIDS

We linked records of 83,434 AIDS cases reported to AIDS registries through 1990 to cancer registry records during times when overlap in registration existed. Of 8,496 Kaposi's-sarcoma (KS) cases meeting enrollment criteria, 1,045 occurred semesters 2 through 4 (6 through 23 months) after another AIDS-defining illness. KS risk in this period after AIDS declined steadily over the 1980s. Adjusting for age, gender, ethnic origin and calendar time period, we found the relative risk (RR) of KS to be 106,000 for homo/bisexual men with AIDS and 13,000 for other men with AIDS. Risk was highest for homo/bisexual men between 30 and 39 years old and among 20- to 29-year-old non-homo/bisexual men. The RR in black men was approximately half that reported in white men among homo-bisexual men and others. Between the second and fourth semester after AIDS, the ratio of RR of KS to that of non-AIDS-related cancers increased 1.5-fold. In a similar analysis, there were 335 non-Hodgkin's lymphoma (NHL) cases in semesters 2 through 4 after AIDS. The overall risk was elevated 283-fold in homo/bisexual men and the RR ratio increased 1.8-fold between semester 2 and 4 after AIDS. In summary, the risk of KS following another AlDS-defining illness is strikingly high, more in white men than in black men, and the risks of KS and, especially, NHL appear to increase with time from AIDS. (This article is a US Government work and, as such, is in the public domain in the United States of America.) © 1996 Wiley-Liss, Inc.

Increasing trend in Type 1 (insulin-dependent) diabetes mellitus in childhood in Finland

The Central Drug Registry in Finland ascertained 5,920 incident cases of Type 1 (insulin-dependent) diabetes mellitus diagnosed under the age of 15 years, during 1965-1984. The incidence was higher for males 29.2/100,000 (95% confidence intervals 28.2-30.2/100,000) than for females 26.1/100,000 (25.1-27.1/100,000). A non-linear increase in incidence with age was confirmed, with peaks at ages 2, 9 and 14 years in males and at 3, 5-6 and 11 years in females. A significant temporal variation in incidence was found, adjusting for age and sex. During 1965 to 1984 the incidence rose by about 57% or by 2.4% annually. However, a non-linear curve with two incidence peaks in 1978 and 1983 would better describe the temporal pattern than a linear trend. There was no significant difference in the temporal variation between males and females. The changes in diabetes risk appeared to affect proportionally all age groups under 15 years. Two possible mechanisms were explored: a calendar period effect vs a birth cohort effect. The calendar time period effect was significant alone and also when adjusted for the birth cohort effect. One the contrary, the birth cohort effect was not significant, when adjusted for the calendar period effect. In conclusion, over the past two decades, the incidence of childhood Type 1 diabetes in Finland has increased by about 57%. The pattern of change was a steady rising background incidence superimposed by sudden outbreaks suggesting environmental causative factors.

Retrospective estimation of diabetes incidence from information in a prevalent population and historical mortality.

If the distribution of onset age of disease in a well-defined prevalent (cross-sectional) population of patients is known, disease incidence rates specific for age and calendar time period may be estimated, assuming known mortality rates and a closed population. This paper develops a method of estimation, illustrates this method on Danish diabetes data, and discusses its general applicability. The prevalent population of diabetic subjects in Fyn County on July 1, 1973 was ascertained from prescriptions, and information on disease onset was obtained from the patients' medical records. In this study only patients with onset of disease before or at age 30 years were studied. The mortality of diabetic subjects in Denmark was estimated from retrospective hospital data covering the period since 1933, and historical age-specific population sizes of Fyn County were obtained from census data. The incidence of diabetes increases with calendar time and with age for most cohorts. The variation with age for a fixed calendar year is more complicated, however, usually displaying a local maximum at about the age of puberty and a higher incidence at the upper end of the studied age range.

Birth cohort analysis using irregular cross-sectional data: a technical note.

Cancer mortality and morbidity data are usually collected and published by calendar time period and by age class. Transformation of the age-specific incidence or mortality rates into those for birth cohorts is readily undertaken when one age class of each time period corresponds to a given cohort: a requirement that is often not satisfied. The authors propose a method for the computation of birth cohort age-specific incidence rates given irregular cross-sectional data. The procedure is based on a cross-sectional interpolation of cumulated population and case figures, from which cohort rates can be derived. Using the method several examples of trends in cancer incidence by birth cohort are discussed.

Exposure of motor vehicle examiners to carbon monoxide: a historical prospective mortality study.

The National Institute for Occupational Safety and Health (NIOSH) investigated the health effects of chronic exposure to low concentrations of carbon monoxide by conducting a historical prospective cohort study of mortality patterns among 1,558 white male motor vehicle examiners who were employed in New Jersey for a minimum of 6 months between 1944 and 1973. Industrial hygiene surveys indicated that the examiners were exposed to carbon monoxide at a time-weighted average (TWA) of 10-24 ppm; the exposure level recommended by NIOSH is 35 ppm TWA. A modified life table technique was used to calculate cause-specific expected deaths for the cohort adjusted for age and calendar time periods. The expected deaths were compared to the number of observed deaths through August 1973. The cohort demonstrated a slight overall increase in cardiovascular disease deaths (124 observed vs. 118.4 expected), but a more pronounced excess was observed within the first 10 yr. following employment (28 observed vs. 20.9 expected). A statistically significant excess of cancer mortality was found for motor vehicle examiners after 30 yr latency (13 observed vs. 6.9 expected, P < 0.5); this excess, however, was not confined to any particular organ site. The number of deaths due to accidents was significantly lower than expected (8 observed vs. 19.6 expected, P < .01).