Physical activity and risk of endometrial cancer in the Norwegian Women and Cancer (NOWAC) study

Abstract

Few studies have investigated the association between endometrial cancer and physical activity (PA) using repeated measures of PA and different subtypes of endometrial cancer. We aimed to investigate the association between endometrial cancer and PA level at two points in time in women with different body mass index (BMI) profiles, and to calculate the population attributable fraction (PAF) of endometrial cancer for low PA levels. We included 82,759 women with complete information on PA at baseline in the Norwegian Women and Cancer Study; 52,370 had follow-up information on PA. 687 endometrial cancer cases were identified. Multivariate cox proportional hazard models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI). The PAF indicated the proportion of endometrial cancer that could be avoided in the population if these women had a higher PA level. There was a statistically significant association between low PA levels at baseline and follow-up and endometrial cancer risk, with a dose-response trend (lowest PA level: HR = 1.60, 95% CI 1.16-2.20; highest PA level: HR = 0.73, 95% CI 0.45-1.16 compared to the median). Analyses that included follow-up measurements yielded similar results. 21.9% (95% CI 7.1-34.3) of endometrial cancers could be avoided if women with low PA levels (≤ 4 in a 1-10 degree self reported PA scale) increased their PA levels to 5-10. We found an inverse dose-response association between PA and endometrial cancer, independent of BMI. In this nationally representative cohort, 21.9% of endometrial cancers could potentially be avoided if PA levels increased to higher PA levels.

Physical Activity in Cancer Prevention and Survival: A Systematic Review

“…(6) Two cohort studies identified in the updated search found statistically significant associations between high versus low levels of physical activity and reduced risk of endometrial cancer. (26,27) Esophageal Cancer: The PAGAC identified three meta-analyses/systematic reviews and one pooled analysis on physical activity and esophageal cancer risk. The most comprehensive was a 2014 meta-analysis(28) that included 24 individual studies of which 9 were cohort and 15 were case-control studies.…”

Risk of lung cancer and physical activity by smoking status and body mass index, the Norwegian Women and Cancer Study

“…Our chained imputation models included all variables for the final Cox proportional hazards regression models and additional variables in order to predict incomplete variables or to predict whether the incomplete variable was missing [57]. This method has been developed and proved robust in several of studies within the NOWAC study [31][32][33]58], and the consistency with the complete-case analysis strengthens the results. Nevertheless, we cannot rule out that some of the information is still missing-not-at-random which may lead to biased estimations.…”

“…The pattern of missing was confirmed arbitrary. We used a similar imputation process as described in previous publications [31][32][33]. To reduce sampling variability, we created 20 replicate datasets from the imputation simulation [34].…”

<p>Excess Body Weight and Incidence of Type 1 and Type 2 Endometrial Cancer: The Norwegian Women and Cancer Study</p>

“…13,14,25,26 The second sensitivity analysis grouped all tumors with morphology code 8140 (EC-not other specified [NOS]) as type 1 EC, except all grade 3+ tumours that were classified as type 2 EC. 10,25,26 By assuming a causal relationship between exposure and outcome as well as independence between risk factors, it is possible to estimate the population attributable fraction (PAF) in a national representative cohort like the NOWAC study. PAF describes the preventable proportion of the disease incidence related to the exposure over a certain time-period.…”