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PubMed1985

Statistical age-period-cohort analysis: a review and critique.

Descriptive and statistical age-period-cohort (APC) analysis methods have received considerable attention in the literature. The statistical modeling of APC data often involves the popular multiple classification model, a model containing the effects of age groups (rows), periods of observation (columns), and birth cohorts (diagonals of the age-by-period table). The identifiability problem inherent to this model is discussed, and its adverse effects on the results of APC modeling exercises are illustrated numerically. Potential problems attendant with the use of two-factor models are described, and other possible modeling approaches currently in use are discussed. Interpretational limitations due to certain innate characteristics of typical APC data sets are also detailed. Given all the documented potential sources for error, the current state-of-the-art regarding the statistical modeling of APC data should be considered to be at an early stage of development.

Adult↗
PubMed1986

[[Cohort analysis of mortality from three major adult diseases]].

The authors present cohort mortality rates for Japan by five-year age interval for all causes of death and for malignant neoplasms, cerebrovascular disease, and heart disease. The calculations are based on vital statistics data for 1947-1982 and period and cohort life tables for 1891-1982 published by Zenjo Nanjo and Kazumasa Kobayashi. "Ratios of individual cause to all causes in each age were calculated and applied to [a] mortality matrix derived from Nanjo-Kobayashi's life tables. Age-specific period and cohort mortality rates for each cause were calculated from [the] cause-specific mortality matrix.... Trends and age patterns of cohort mortalities and ratios of mortalities in successive cohort and age group were investigated." (SUMMARY IN ENG)

Age Factors↗
PubMed1999

Exposure to natural fluoride in well water and hip fracture: a cohort analysis in Finland.

In the retrospective cohort study based on record linkage, the authors studied a cohort of persons born in 1900-1930 (n = 144,627), who had lived in the same rural location at least from 1967 to 1980. Estimates for fluoride concentrations (median, 0.1 mg/liter; maximum, 2.4 mg/liter) in well water in each member of the cohort were obtained by a weighted median smoothing method based on ground water measurements. Information on hip fractures was obtained from the Hospital Discharge Registry for 1981-1994. No association was observed between hip fractures and estimated fluoride concentration in the well water in either men or women when all age groups were analyzed together. However, the association was modified by age and sex so that among younger women, those aged 50-64 years, higher fluoride levels increased the risk of hip fractures. Among older men and women and younger men, no consistent association was seen. The adjusted rate ratio was 2.09 (95% confidence interval: 1.16, 3.76) for younger women who were the most exposed (>1.5 mg/liter) when compared with those who were the least exposed (< or =0.1 mg/liter). The results suggest that fluoride increases the risk of hip fractures only among women.

Aged↗
PubMed2002

[Active life expectancy in Germany and in the United States. A cohort analysis based on the "German Socio-Economic Panel" (GSOEP) and the "Panel Study of Income Dynamics" (PSID)].

Using the method of multistate life-tables, the article presents results on active life expectancy on the basis of the German Socio-Economic Panel (GSOEP) and the Panel Study of Income Dynamics (PSID). The transitions into and out of active life are based on event-history analysis and are calculated for different cohorts. Compared to cross-sectional analysis, the longitudinal analysis carried out here describes active life expectancy with reference to single birth cohorts. Results show that in Germany there has been substantial improvement in active life expectancy while in the USA there has been some deterioration.

Activities of Daily Living↗
PubMed2005

Stillbirths in the United States, 1981-2000: an age, period, and cohort analysis.

OBJECTIVES: We examined age, period, and cohort (APC) effects on temporal trends in stillbirths among Black and White women in the United States. METHODS: We conducted a cohort study of Black and White women who delivered a singleton live-born or stillborn infant during 1981 through 2000. We analyzed stillbirth rates at 20 or more weeks of gestation within 7 age groups, 4 periods, and 10 "central" birth cohorts after adjusting for confounders. RESULTS: In both racial groups, women younger than 20 years or 35 years or older were at increased risk of stillbirth; risks decreased over successive periods in all age groups. Birth cohort had no impact on stillbirth trends among Blacks and only a small, nonsignificant effect among Whites. Analyses of various APC combinations showed that Blacks were at a 1.2- to 2.9-fold increased risk for stillbirth relative to Whites. Attributable fractions for stillbirth because of age, period, and cohort effects were 16.5%, 24.9%, and 0.1%, respectively, among Black women and 14.5%, 36.2%, and 2.1%, respectively, among White women. CONCLUSIONS: Strong effects of age and period were observed in stillbirth trends, but these factors do not explain the persistent stillbirth disparity between Black and White women.

Adolescent↗
PubMed1999

An age-period-cohort analysis of 50,875 AIDS cases among injecting drug users in Europe.

BACKGROUND: The long average incubation time from HIV infection to AIDS makes it difficult to estimate recent HIV transmission from AIDS incidence data. Age-period-cohort (APC) analysis can separate out the effects of age, calendar time and birth cohort to provide a clearer picture of transmission trends. METHODS: AIDS incidence data from 1981 to 1994 among intravenous drug users (IDU) for 12 Western European countries were used. Yearly incidences per 100,000 population or 100,000 person-years were calculated by age at diagnosis and 5-year birth cohort (1950-1954, 1955-1959, 1960-1964, 1965-1969 and 1970-1974), and corrected for reporting delay. Incidence patterns were compared between birth cohorts and countries. RESULTS: For most countries the impact was greatest on the cohort born 1960-1964. Comparing incidence patterns in the 1965-1969 to 1960-1964 cohorts suggest the epidemic has plateaued at low to intermediate levels in Austria, Greece and the North-Western European countries, and at high levels in France, Italy and Switzerland. For most countries transmission amongst the 1970-1974 as compared to the 1965-1969 cohorts could not be assessed due to small numbers and short follow-up time. In Spain the epidemic was uncontrolled with a high incidence among recent birth cohorts. In Portugal the epidemic was still at an early and expanding phase. CONCLUSIONS: The APC analysis revealed large country differences in the dynamics of the HIV/AIDS epidemic among IDU. Full interpretation of these differences is dependent on information from other sources about the local public health response and trends in drug injecting behaviours. Earlier introduction of the virus and higher prevalence of injecting drug use may explain some of the generally higher incidence in Southern European countries, but the larger part of it is most likely explained by local characteristics of drug users, such as younger age and more frequent sharing of needles and syringes, and a less effective public health response.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Age-period-cohort analysis of pulmonary tuberculosis mortality in Taiwan: 1961 to 1990.

The specific aim of this study was to examine the effects of age, calendar period of death, and birth cohort in pulmonary tuberculosis (TB) mortality in Taiwan during the period 1961 to 1990. A log-linear Poisson regression model modified from the method of Osmond and Gardner was used and 79,881 deaths (58,025 males and 21,856 females) were included in the analysis. Birth cohort is the most significant predictor of pulmonary TB mortality according to the model. The earliest birth cohort from 1891 had a pulmonary TB mortality 17,327 and 6,186 times those born from 1986 for males and females, respectively. There was also a significant age effect. The youngest age group of zero to four years had a pulmonary TB mortality 7.10 and 5.87 times those for the age group of five to nine years for males and females, respectively. The oldest age group of 70 to 74 years had a risk of pulmonary TB mortality 2.89 and 1.88 times those for the five- to nine-year age groups for males and females, respectively. Parameters of the period factor showed a decreasing pulmonary TB mortality from 1961 to 1990 that was less significant than those of age or cohort. In addition to the improvement in medical measures that influenced the effect of calendar year on TB mortality, year of birth is an important determinant in the trend of TB mortality in Taiwan. The result shows that the major focus for TB mortality in Taiwan is in the age groups born between 1891 and 1921.

Adolescent↗
PubMed1986

Cohort analysis of Ontario suicide rates, 1877-1976.

Birth cohort studies of suicide rates in Alberta, the United States and Australia indicate that within each generation, suicide rates increase with age. Such studies argue that cohort-specific suicidal risk, together with present high suicide rates among young people predict even higher rates as these generations grow older. Ontario data from a 100-year period demonstrate that within birth cohorts suicide rates consistently increase with age, peak between ages 50 and 70, then decline. Gradual increases in mean suicide rates result in every birth cohort having higher suicide rates than the preceding cohort at almost every age level. These trends combine to produce a regular birth cohort effect and a steady shift in cross-sectional data to higher rates of suicide among younger age groups. Abrupt increases in suicide rates occurring during the Great Depression had only transient effects on birth cohort and cross-sectional curves. Results provide weak support for the hypothesis of cohort-specific suicidal risk and clarify the factors which produce birth cohort effects.

Adolescent↗
PubMed2003

Secular trends in adolescent never smoking from 1990 to 1999 in California: an age-period-cohort analysis.

OBJECTIVES: We analyzed age, time period, and cohort effects on trends in adolescent cigarette smoking in California from 1990 to 1999. METHODS: Data from subjects aged 12 to 17 years (n = 26 536; 50.4% male) from the California Tobacco Survey and the California Youth Tobacco Survey were analyzed, and never smokers were used as the outcome measure. RESULTS: The proportion of never smokers increased from 60% for males and 66% for females in 1990 to around 70% for both sexes in 1999. Respondents were more likely to be never smokers if born in 1978 or later (i.e., aged 12 years or younger in 1990, when most tobacco control programs started in California). CONCLUSIONS: The statewide antitobacco programs prevented adolescents from starting to smoke, primarily through a cohort effect.

Adolescent↗
PubMed2004

Variations in the risk of disability pension in Norway 1970-99. A gender-specific age-period-cohort analysis.

AIMS: A study was undertaken to investigate whether cohort or period effects could explain the varying and generally increasing incidence of disability pension in Norway between 1970 and 1999. METHODS: The study used data from a complete national register of new disability cases in Norway, including all cases of disability pension in the 16-60 age group categorized according to age and gender for each year from 1970 to 1999. The population at risk was defined for each year from census data and number of individuals already receiving disability pension. Data were organized in five-year age groups, five-year time periods and corresponding overlapping nine-year birth cohorts. Age- and gender-specific rates were displayed graphically for periods and cohorts. Separate Poisson regression models were fitted for age periods and age cohorts. Finally a combined age, period, and cohort model was applied. RESULTS: The overall incidence was 7.4/1,000 non-disabled persons per year for women and 6.0/1,000 for men. For women 52.1% of the cases were in the 51-60 age group, whereas the corresponding figure for men was 57.6%. Statistical analysis showed an increasing trend for both genders, more pronounced for women than men. All time periods deviated significantly from the trend, either upwards or downwards. Age-cohort models showed less variation, but recent cohorts had higher than expected rates, especially for men. CONCLUSIONS: Further studies should investigate why Norwegian women were more affected by the period effects than men. An increasing incidence of disability pension among recent cohorts is a major challenge for the Norwegian welfare system.

Adolescent↗
PubMed1996

Age cohort analysis of the 20th century decline in U.S. farm numbers.

"The demographic component of the decline in U.S. farm numbers is analysed by tracking the size of farm operator age cohorts.... Cohort profiles indicate an inverted U-shape in the relationship between farm numbers and cohort age. Successive cohorts have been smaller than their predecessors, and withdrawal rates of older operators have fallen in recent years. Projections based on entry-withdrawal patterns for 1987-1992 suggest decline in farm numbers from 1.93 million in 1992 to 1.48 million in 2002 and 1.29 million in 2007. Imbalance between withdrawing older operators and younger new entrants could encourage a broadening of the pool of farm entrants and changes in farm ownership, operating and financing arrangements."

Age Factors↗
PubMed2006

Impact of lamivudine on the risk of liver-related death in 2,041 HBsAg- and HIV-positive individuals: results from an inter-cohort analysis.

BACKGROUND: The impact of lamivudine (3TC) as part of combination antiretroviral therapy (cART) on the risk of liver-related death (LRD) in HIV/hepatitis B virus (HBV)-coinfected patients has not been extensively studied. METHODS: We performed an analysis involving HIV/HBV-coinfected patients in 13 cohorts who initiated cART. The end-point was LRD--that is, death with concomitant decompensated liver disease (DLD) or hepatocellular carcinoma--as the main cause. Incidence rates of LRD after initiation of cART were expressed as number of events per 100 person-years of follow-up (PYFU). A Poisson regression model adjusted for cohort, gender, mode of HIV transmission, CD4+ T-cell count at cART initiation, liver disease pre-cART, duration of 3TC before cART, and hepatitis C virus was used to assess the association between use of 3TC and risk of LRD. RESULTS: We analysed 2,041 patients. Follow-up after starting cART was 7,648 PYFU (5,569 spent on 3TC-containing regimens) with a median per person of 48 months (range: 2-91). Of the total, 217 subjects died; 57 deaths were liver-related resulting in a rate of 7.5 per 1,000 PYFU [95% confidence intervals (CI): 5.6-9.7]. The relative risk of LRD per extra year of 3TC use was 0.73 (95% CI: 0.59-0.90, P = 0.004). CONCLUSION: The use of 3TC was associated with a reduced risk of LRD over 4 years of follow-up. This study supports the current view that the use of 3TC as part of cART should be considered in patients who are tested positive for HBsAg.

Adult↗
PubMed1985

[Cohort analysis of cervical cancer mortality in Austria].

Cytological screening has reduced mortality of cervical cancer in Austria. It has cut mortality of carcinoma of the uterus by one third from 1966 to 1982. In causes of deaths screening has mainly reduced mortality from cancer of other and unspecified parts of uterus. A new nomenclature introduced in 1969 has strengthened the decreasing trend with regard to cancer of other and unspecified parts of uterus and has compensated the screening effect in mortality from cervical carcinoma (the decreasing trend was preceded by an increase). This shift of cervix cancer deaths cases from the position mortality from cancer of other and unspecified parts of uterus to mortality from cervical cancer is the reason that the latter does not reflect the real trend of cervical cancer mortality. The analysis of cervical cancer by birth cohort and age at death (1966-1981) show the effect of screening in the younger births cohorts of age groups 40-44, 45-49 and 50-54 and in older ages of cohorts born in 1927-1932, 1932-1936 and 1937-1941 respectively.

Adult↗
PubMed2002

The clinical relevance of non-nucleoside reverse transcriptase inhibitor hypersusceptibility: a prospective cohort analysis.

OBJECTIVE: To evaluate the clinical significance of hypersusceptibility to non-nucleoside reverse transcriptase inhibitors (NNRTI). DESIGN: Analysis of a prospective clinical trial cohort. PATIENTS: NNRTI-naive patients failing a stable antiretroviral regimen. MEASUREMENTS: HIV phenotype, HIV RNA, and CD4 cell counts were prospectively collected after patients changed to a new regimen. Hypersusceptibility to NNRTI was defined as a fold-change (FC) in IC50 (inhibitory concentration of 50%) of < 0.4. RESULTS: The 177 patients had a mean HIV RNA of 4.1 log10 copies/ml, CD4 cell count of 322 x 10(6) cells/l and 41 months of prior antiretroviral treatment. Hypersusceptibility to one or more NNRTI was present in 29%. Both longer duration and reduced susceptibility to nucleoside reverse transcriptase inhibitors were associated with efavirenz hypersusceptibility (P < 0.05). NNRTI-containing regimens were initiated in 106 patients at baseline. The mean change in log HIV RNA after 6 months was greater for patients with hypersusceptibility (-1.2 log10 copies/ml; n = 21) than in patients without (-0.8 log10 copies/ml; n = 77) (P = 0.016). Differences persisted to month 12 (P = 0.023). Multiple linear regression models confirmed that hypersusceptibility to NNRTI was a significant independent predictor of the magnitude of early (months 1-4) HIV RNA reduction, after accounting for the baseline HIV RNA and the number of drugs to which the patient's virus was susceptible (P < 0.02). CD4 cell increases (months 4-10) were 28- 60 x 10(6) cells/l greater in patients with hypersusceptible virus (P < or = 0.1). CONCLUSION: NNRTI hypersusceptibility occurred in more than 20% of nucleoside-experienced patients and was associated with greater reduction of HIV RNA and increase in CD4 cells.

Adult↗
PubMed1987

Age, period and cohort analysis of trends in mortality from major diseases in Japan, 1955 to 1979: peculiarity of the cohort born in the early Showa Era.

Japanese researchers have reported that recent mortality rates from diabetes mellitus, ischemic heart disease, peptic ulcer, cirrhosis of the liver and suicide for middle-aged Japanese men have increased by comparison with those for other age groups. There has been some controversy over the etiology of this unusual trend, and in particular whether it is due primarily to recent undesirable socio-economic factors (period effects) or to factors specific to these cohorts born in the early Showa Era, around 1925 to 1940 (cohort effects). A possible source of this controversy lies in the methods which have been used to describe the trends; these are mostly descriptive and graphical. To elucidate which factors are responsible for these trends, we analysed the mortality data quantitatively applying an age-period-cohort model modified so that period effects remain constant within certain age groups but may vary from one age group to the next. Although the identifiability problem still occurs in the modified model, estimable curvature components of time effects may be used to examine these unusual trends. In fact, the peculiarity of the cohort born in the early Showa Era was clearly detected by the curvature components of cohort effects for these major diseases. These findings are consistent with the 'cohort hypothesis' for the recent peculiar trend in Japanese male mortality.

Adult↗