| 1. |
- Bellavia, Andrea, et al.
(författare)
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Using Laplace Regression to Model and Predict Percentiles of Age at Death When Age Is the Primary Time Scale
- 2015
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Ingår i: American Journal of Epidemiology. - : OXFORD UNIV PRESS INC. - 0002-9262 .- 1476-6256. ; 182:3, s. 271-277
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Tidskriftsartikel (refereegranskat)abstract
- Increasingly often in epidemiologic research, associations between survival time and predictors of interest are measured by differences between distribution functions rather than hazard functions. For example, differences in percentiles of survival time, expressed in absolute time units (e.g., weeks), may complement the popular risk ratios, which are unitless measures. When analyzing time to an event of interest (e.g., death) in prospective cohort studies, the time scale can be set to start at birth or at study entry. The advantages of one time origin over the other have been thoroughly explored for the estimation of risks but not for the estimation of survival percentiles. In this paper, we analyze the use of different time scales in the estimation of survival percentiles with Laplace regression. Using this regression method, investigators can estimate percentiles of survival time over levels of an exposure of interest while adjusting for potential confounders. Our findings may help to improve modeling strategies and ease interpretation in the estimation of survival percentiles in prospective cohort studies.
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| 2. |
- Bellavia, Andrea
(författare)
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A percentile approach to time-to-event outcomes
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Evaluating survival percentiles is a possible approach for the analysis of time-to-event outcomes that moves the focus from risk to time, as the proportion of events is xed and the time by which that proportion is achieved is investigated. The development of statistical methods for conditional censored quantiles has opened up the possibility to use this approach in epidemiological studies. The aim of this doctoral thesis was to investigate the advantages of this method in epidemiology, by evaluating survival percentiles in observational studies on lifestyle and mortality, and by extending and further developing the statistical tools for the estimation of conditional survival percentiles. The percentile approach was used in a large prospective cohort of about 80.000 middle-aged and elderly Swedish men and women, with 15 years of follow-up during which 20% of the study pop- ulation died. The impact of modi able lifestyle factors such as fruit and vegetables consumption (Study I), sleep duration and physical activity (Study II), and processed and non-processed red meat consumption (Study III) on time to death were evaluated. Statistical modeling of conditional survival percentiles was conducted using Laplace regression. The epidemiological measure of exposure-outcome association was de ned in terms of percentile di erence (PD). Quantitative exposures were exibly modeled using splines to investigate the dose-response shape. Low fruit and vegetables consumption (Study I) was found to be associated with progressively shorter survival up to 3 years (PD: -37 months; 95% CI: -58, -16) when comparing those who con- sumed 5 servings/day and those who never consumed fruit and vegetables. Long sleep duration, over 8 hours/day, (Study II) was associated with shorter survival (PD = -20 months; 95% CI: -30, -11) among those with low physical activity, comparing with those with 7 hours of sleeping per day. In Study III, compared with no consumption, higher intake of processed red meat (200 g/d) was associated with shorter survival (PD: -10 months; 95% CI: -18, -3). High and moderate intakes of non-processed red meat were associated with shorter survival only when accompanied by a high intake of processed red meat. Study IV and Study V introduced novel developments and extensions of the percentile approach. Study IV presented the meaning and evaluation of survival percentiles in those situations where the time variable of interest is attained age at the event rather than follow-up time. This change in the time-scale has important consequences on the de nition and interpretation of the survival curve and related percentiles. The study described how to use multivariable Laplace regression models to esti- mate percentiles of age at death conditioning on age at entry into the study, exposures, and potential confounders. Study V focused on interaction analysis. Interaction can be evaluated on the additive or multiplicative scale, but its assessment in prospective studies is commonly limited to the multiplica- tive scenario. In this study the advantages of using a percentile approach in interaction analysis were presented. A measure of interaction in terms of time was introduced and how Laplace regression can be used to estimate a measure of interaction on the additive scale was described. Evaluating survival percentiles provides an intuitive and exible approach for the analysis of time- to-event outcomes. With this method, results from prospective studies can be presented in terms of di erences in survival time, facilitating both interpretation and communication of scienti c ndings. The introduction of a statistical technique to estimate conditional survival percentiles has substan- tially enriched its potentialities and eased its application in epidemiological research. The percentile approach should be considered as a possible complement to classical approaches and its use should be widespread.
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| 3. |
- Bellavia, Andrea, et al.
(författare)
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Alcohol consumption and mortality : a dose-response analysis in terms of time
- 2014
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Ingår i: Annals of Epidemiology. - : ELSEVIER SCIENCE INC. - 1047-2797 .- 1873-2585. ; 24:4, s. 291-296
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Low-to-moderate alcohol consumption is associated with decreased mortality. However, many aspects of this association are still debated. Our aim was to complement available information by conducting a dose-response analysis of the association between alcohol consumption and survival time. Methods: In a Swedish population-based cohort of 67,706 middle-aged and elderly men and women, frequency and amount of drinking were assessed through a self-administrated questionnaire. During 15 years of follow-up, 13,323 participants died. Differences in survival (10th percentile differences, PDs) according to levels of alcohol consumption were estimated using Laplace regression. Results: We found evidence of nonlinearity between alcohol consumption and survival. Among women, we observed a rapid increase in survival up to 6 g/d of alcohol consumption (0.5 drinks/d) where survival was 17 months longer (PD = 17 months, 95% confidence interval, 10 to 24). After this peak, higher alcohol consumption was progressively associated with shorter survival. Among men, survival improved up to 15 g/d (1.5 drinks/d) where we observed a PD of 15 months (95% confidence interval, 8 to 22). Conclusions: Low alcohol consumption was associated with improved survival up to 1.5 years for women with an average consumption of 0.5 drinks per day and to 13 years for men with an average consumption of 1.5 drinks per day. (C) 2014 Elsevier Inc. All rights reserved.
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| 4. |
- Bellavia, Andrea, et al.
(författare)
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Association between chemical mixtures and female fertility in women undergoing assisted reproduction in Sweden and Estonia
- 2023
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Ingår i: Environmental Research. - : Elsevier. - 0013-9351 .- 1096-0953. ; 216:Part 1
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Women of reproductive age are exposed to ubiquitous chemicals such as phthalates, parabens, and per -and polyfluoroalkyl substances (PFAS), which have potential endocrine disrupting properties and might affect fertility. Our objective was to investigate associations between potential endocrine-disrupting chemicals (EDCs) and female fertility in two cohorts of women attending fertility clinics.Methods: In a total population of 333 women in Sweden and Estonia, we studied the associations between chemicals and female fertility, evaluating ovarian sensitivity index (OSI) as an indicator of ovarian response, as well as clinical pregnancy and live birth from fresh and frozen embryo transfers. We measured 59 chemicals in follicular fluid samples and detected 3 phthalate metabolites, di-2-ethylhexyl phthalate (DEHP) metabolites, 1 paraben, and 6 PFAS in > 90% of the women. Associations were evaluated using multivariable-adjusted linear or logistic regression, categorizing EDCs into quartiles of their distributions, as well as with Bayesian Kernel Ma-chine Regression.Results: We observed statistically significant lower OSI at higher concentrations of the sum of DEHP metabolites in the Swedish cohort (Q4 vs Q1, beta =-0.21, 95% CI:-0.38,-0.05) and methylparaben in the Estonian cohort (Q3 vs Q1, beta =-0.22, 95% CI:-0.44,-0.01). Signals of potential associations were also observed at higher concentrations of PFUnDA in both the combined population (Q2 vs. Q1,beta =-0.16, 95% CI-0.31,-0.02) and the Estonian population (Q2 vs. Q1,beta =-0.27, 95% CI-0.45,-0.08), and for PFOA in the Estonian population (Q4 vs. Q1, beta =-0.31, 95% CI-0.61,-0.01). Associations of chemicals with clinical pregnancy and live birth presented wide confidence intervals.Conclusions: Within a large chemical mixture, we observed significant inverse associations levels of DEHP me-tabolites and methylparaben, and possibly PFUnDA and PFOA, with OSI, suggesting that these chemicals may contribute to altered ovarian function and infertility in women.
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| 5. |
- Bellavia, Andrea, et al.
(författare)
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Differences in age at death according to smoking and age at menopause
- 2016
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Ingår i: Menopause. - : LIPPINCOTT WILLIAMS & WILKINS. - 1072-3714 .- 1530-0374. ; 23:1, s. 108-110
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Younger age at menopause is associated with overall mortality, and cigarette smoking is the only lifestyle factor influencing this association. However, the combined effects of age at menopause and smoking have never been quantified in terms of survival time. Our aim was to evaluate, in a large cohort of Swedish women, differences in age at death according to age at menopause and smoking status. Methods: Age at menopause and smoking were assessed, using a self-administered questionnaire, in a population-based cohort of 25,474 women aged 48 to 83 years. Laplace regression was used to calculate differences in median age at death (50th percentile difference [PD]) according to smoking and age at menopause. Results: Across 16 years of follow-up, 5,942 participants died. The difference in median age at death between women with menopause at 40 years and women with menopause at 60 years was 1.3 years (50th PD, 1.3; 95% CI, 0.3-2.2). Compared with current smokers, former smokers and never smokers had older median age at death-2.5 years (50th PD, 2.5; 95% CI, 1.9-3.1) and 3.6 years (50th PD, 3.6; 95% CI, 3.1-4.1), respectively. When analysis was restricted to current smokers, the difference in age at death between women with menopause at 40 years and women with menopause at 60 years increased to 2.6 years (50th PD, 2.6; 95% CI, 0.8-4.5). No association among never smokers was observed. Conclusions: Younger age at menopause is linearly associated with shorter survival. This association tends to be stronger among current smokers.
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| 6. |
- Bellavia, Andrea, et al.
(författare)
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Differences in survival associated with processed and with nonprocessed red meat consumption
- 2014
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Ingår i: American Journal of Clinical Nutrition. - : OXFORD UNIV PRESS. - 0002-9165 .- 1938-3207. ; 100:3, s. 924-929
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Tidskriftsartikel (refereegranskat)abstract
- Background: High red meat consumption is associated with an increased mortality risk. This association is partly explained by the negative effect of processed meat consumption, which is widely established. The role of nonprocessed meat is unclear. Objective: The objective was to examine the combined association of processed and nonprocessed meat consumption with survival in a Swedish large prospective cohort. Design: In a population-based cohort of 74,645 Swedish men (40,089) and women (34,556), red meat consumption was assessed through a self-administered questionnaire. We estimated differences in survival [15th percentile differences (PDs), differences in the time by which the first 15% of the cohort died] according to levels of total red meat and combined levels of processed and nonprocessed red meat consumption. Results: During 15 y of follow-up (January 1998 to December 2012), we documented 16,683 deaths (6948 women; 9735 men). Compared with no consumption, consumption of red meat >100 g/d was progressively associated with shorter survival-up to 2 y for participants consuming an average of 300 g/d (15th PD: -21 mo; 95% CI: -31, -10). Compared with no consumption, high consumption of processed red meat (100 g/d) was associated with shorter survival (15th PD: -9 mo; 95% CI: -16, -2). High and moderate intakes of nonprocessed red meat were associated with shorter survival only when accompanied by a high intake of processed red meat. Conclusions: We found that high total red meat consumption was associated with progressively shorter survival, largely because of the consumption of processed red meat. Consumption of nonprocessed red meat alone was not associated with shorter survival. The Swedish Mammography Cohort and the Cohort of Swedish Men were registered at clinicaltrials.gov as NCT01127698 and NCT01127711, respectively.
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| 7. |
- Bellavia, Andrea, et al.
(författare)
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Fruit and vegetable consumption and all-cause mortality : a dose-response analysis.
- 2013
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Ingår i: American Journal of Clinical Nutrition. - : Elsevier BV. - 0002-9165 .- 1938-3207. ; 98:2, s. 454-459
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The association between fruit and vegetable (FV) consumption and overall mortality has seldom been investigated in large cohort studies. Findings from the few available studies are inconsistent.OBJECTIVE: The objective was to examine the dose-response relation between FV consumption and mortality, in terms of both time and rate, in a large prospective cohort of Swedish men and women.DESIGN: FV consumption was assessed through a self-administrated questionnaire in a population-based cohort of 71,706 participants (38,221 men and 33,485 women) aged 45-83 y. We performed a dose-response analysis to evaluate 10th survival percentile differences (PDs) by using Laplace regression and estimated HRs by using Cox regression.RESULTS: During 13 y of follow-up, 11,439 deaths (6803 men and 4636 women) occurred in the cohort. In comparison with 5 servings FV/d, a lower consumption was progressively associated with shorter survival and higher mortality rates. Those who never consumed FV lived 3 y shorter (PD: -37 mo; 95% CI: -58, -16 mo) and had a 53% higher mortality rate (HR: 1.53; 95% CI: 1.19, 1.99) than did those who consumed 5 servings FV/d. Consideration of fruit and vegetables separately showed that those who never consumed fruit lived 19 mo shorter (PD: -19 mo; 95% CI: -29, -10 mo) than did those who ate 1 fruit/d. Participants who consumed 3 vegetables/d lived 32 mo longer than did those who never consumed vegetables (PD: 32 mo; 96% CI: 13, 51 mo).CONCLUSION: FV consumption <5 servings/d is associated with progressively shorter survival and higher mortality rates. The Swedish Mammography Cohort and the Cohort of Swedish Men were registered at clinicaltrials.gov as NCT01127698 and NCT01127711, respectively.
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| 8. |
- Bellavia, Andrea, et al.
(författare)
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High red meat intake and all-cause cardiovascular and cancer mortality : is the risk modified by fruit and vegetable intake?
- 2016
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Ingår i: American Journal of Clinical Nutrition. - : OXFORD UNIV PRESS. - 0002-9165 .- 1938-3207. ; 104:4, s. 1137-1143
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Tidskriftsartikel (refereegranskat)abstract
- Background: High red meat consumption is associated with a shorter survival and higher risk of cardiovascular disease (CVD), cancer, and all-cause mortality. Fruit and vegetable (FV) consumption is associated with a longer survival and lower mortality risk. Whether high FV consumption can counterbalance the negative impact of high red meat consumption is unknown. Objective: We evaluated 2 large prospective cohorts of Swedish men and women (the Swedish Mammography Cohort and the Cohort of Swedish Men) to determine whether the association between red meat consumption and the risk of all-cause, CVD, and cancer specific mortality differs across amounts of FV intake. Design: The study population included 74,645 Swedish men and women. Red meat and FV consumption were assessed through a self-administered questionnaire. We estimated HRs of all-cause, CVD, and cancer mortality according to quintiles of total red meat consumption. We next investigated possible interactions between red meat and FV consumption and evaluated the dose-response associations at low, medium, and high FV intake. Results: Compared with participants in the lowest quintile of total red meat consumption, those in the highest quintile had a 21% increased risk of all-cause mortality (HR: 1.21; 95% CI: 1.13, 1.29), a 29% increased risk of CVD mortality (BR: 1.29; 95% CI: 1.14, 1.46), and no increase in the risk of cancer mortality (HR: 1.00; 95% CI: 0.88, 1.43). Results were remarkably similar across amounts of FV consumption, and no interaction between red meat and FV consumption was detected. Conclusion: High intakes of red meat were associated with a higher risk of all-cause and CVD mortality. The increased risks were consistently observed in participants with low, medium, and high FV consumption. The Swedish Mammography Cohort and the Cohort of Swedish Men were registered at clinicaltrials.gov as NCT01127698 and NCT01127711, respectively.
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| 9. |
- Bellavia, Andrea, et al.
(författare)
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Physical activity and mortality in a prospective cohort of middle-aged and elderly men - : a time perspective.
- 2013
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Ingår i: International Journal of Behavioral Nutrition and Physical Activity. - : Springer Science and Business Media LLC. - 1479-5868. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Higher physical activity (PA) levels are known to be associated with lower risk of death. Less attention, however, has been paid to directly evaluate the effect of PA on the time by which a certain fraction of the population has died.METHODS: A population-based cohort of 29,362 men 45 to 79 years of age was followed from January 1998 to December 2010. A total of 4,570 men died. PA was assessed through a self-administrated questionnaire. Adjusted differences in the number of months by which 10% (10th percentile) of the cohort has died, according to levels of total PA (TPA) and different domains of PA were estimated using Laplace regression.RESULTS: Overall, the 10th survival percentile was 9.6 years, that is, 90% of the cohort lived longer than 9.6 years. We found a strong evidence of non-linearity between TPA and the 10th survival percentile (P-value < 0.001). Compared to men with the lowest TPA (29 metabolic equivalents (MET)-hrs/day), men with a median TPA (41 MET-hrs/day) had 30 months longer survival (95% CI: 25-35). Below the median TPA, every increment of 4 MET-hrs/day, approximately a 30 minutes brisk pace daily walk, was associated with a longer survival of 11 months (95% CI: 8-15). Above the median TPA additional activity was not significantly associated with better survival.CONCLUSIONS: We found that a physically active lifestyle is associated with a substantial improvement in survival time, up to 2.5 years over 13 years of follow-up.
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| 10. |
- Bellavia, Andrea, et al.
(författare)
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Quantifying the benefits of Mediterranean diet in terms of survival.
- 2016
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Ingår i: European Journal of Epidemiology. - : Springer Science and Business Media LLC. - 0393-2990 .- 1573-7284. ; 31:5, s. 527-30
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Tidskriftsartikel (refereegranskat)abstract
- Beneficial effects of Mediterranean diet (MD) have been consistently documented. However, to fully understand the public health implications of MD adherence, an informative step is to quantify these effects in terms of survival time differences. The aim of this study was to evaluate the impact of MD on survival, presenting results in terms of differences in median age at death. We used data from 71,333 participants from a large population-based cohort of Swedish men and women, followed-up between January 1, 1998, and December 31, 2012. A total score of MD, ranging from 0 to 8, was calculated by including information on vegetables and fruits consumption, legumes and nuts, non-refined/high fiber grains, fermented dairy products, fish, red meat, use of olive oil/rapeseed oil, and moderate alcohol intake. Multivariable-adjusted differences in median age at death were estimated with Laplace regression and presented as a function of the MD score. During 15 years of follow-up we documented 14,697 deaths. We observed a linear dose-response association between the MD score and median age at death, with higher score associated with longer survival. The difference in median age at death between participants with the extreme scores (0 vs 8) of MD was up to 2 years (23 months, 95 % CI: 16-29). In this study we documented that adherence to MD may accrue benefits up to 2 years of longer survival.
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