br level of sufficient physical
level of sufficient physical activity was defined as 21 MET-hours per week (MET-h/week; 0.5 h × 7 days × 6 MET). Doing so, we adopted a similar approach to that applied in previous studies on this topic [15,16]. Using the ENNS data, we estimated six categories of in-sufficient physical activity: > 0– < 3.5; 3.5– < 7; 7– < 10.5; 10.5– < 14; 14– < 17.5 and 17.5–21 MET-hour per week (Table 1). In secondary analyses, we estimated the proportion and number of cancer cases attributable to insufficient physical activity where the latter was defined following the recommendation of the World Health Organiza-tion (WHO), corresponding to 30 min of moderate-to-vigorous physical activity five days per week (15 MET-hours per week computed as 0.5 h × 5 days × 6 METs). Furthermore, we investigated the number of cancer cases that could have been avoided if everybody would achieve at least half of the physical activity level recommended in France (10.5 MET-hours per week).
2.2. Relative risk estimates
Cancer sites with convincing or probable evidence to be causally associated with insufficient physical activity as reported by the World Cancer Research Fund (WCRF) and the French Cancer Institute (INCa) were included, namely colon (ICD-10: C18), postmenopausal breast (C50) and corpus uteri (C54) cancer [1–3,7]. Relative risks (RRs) for recreational physical activity were obtained from the WCRF Continuous Update Project for postmenopausal breast and colon cancer [1,2] and from a published meta-analysis for endometrial cancer . The sources and RRs are presented in Annex Table 1 in Supplementary material.
The increase in risk for the 1185888-32-7 of 1 MET-hour of physical activity per week was estimated by assuming a log-linear relationship between exposure and risk, so that:
Excess risk per 1 MET-hour deficit per week = ln(1/RRx)/x (1) where x is the exposure level (in MET-hours per week) and RRx is the relative risk for x MET-hours per week. The increase in risk for a decrease of 1 MET-hour of moderate-to-vigorous physical activity per week for colon cancer, post-menopausal breast cancer and endometrial cancer were 4.041e-3, 4.351e-3 and 6.734e-3, respectively. RRs were then calculated for every MET-hour deficit category using the following formula:
RR = exp(excess risk per 1 MET-hour deficit per week * deficit in
where the deficit in MET-hours per week is the midpoint of the MET-hours deficit category (e.g., a deficit of 8.75 MET-hours in the 7–10.5 MET-hour deficit category).
2.3. Cancer incidence data
The number of new cancer cases in France in 2013 by age, sex and
In 2015, an estimated number of 2973 cancer cases diagnosed in French adults were attributable to insufficient levels of physical ac-tivity, corresponding to 0.8% of all cancer cases. In absolute terms, the greatest numbers of cancer cases attributable to insufficient physical activity were postmenopausal breast cancer (1620 cases, or 3.8% of the total breast cancer diagnoses) and colon cancer (902 cases, or 3.6% of
Estimates of the proportion of French adults meeting the physical activity recommendations ranged between 40–49% in men and 31–46% in women depending on age (Table 1). While overall activity levels were rather constant across age groups, larger physical activity deficits were observed at ages 70y+. In 2015, an estimated number of 2973 cancer cases were attribu-table to insufficient physical activity in French adults aged 30y+, corresponding to 0.8% of all cancer cases (Table 2). This comprised 1620 postmenopausal breast cancer cases, 902 colon cancer cases (463 in men and 439 in women) and 450 corpus uteri cancers. The overall PAF was higher in women than in men (1.6% vs 0.2%, respectively) and ranged from 3.6% for colon, to 3.8% for postmenopausal breast and 6.0% for corpus uteri cancers. Secondary analyses, using the WHO recommendation of 15 MET-hours per week for physical activity as reference, resulted in 1786 cases attributable to insufficient physical activity (PAF = 0.5%) (Table 2). If at least half of the recommended physical activity level was achieved in the French population (10.5 MET-hours per week), about 1095 cancer cases (PAF = 0.3%) could have been avoided.
where px is the proportion of population with insufficient physical activity category x and RRx the relative risk (from Eq. (2)) for insufficient physical activity category x. The number of cancer cases attributable to insufficient physical activity was derived by multiplying age-, sex- and cancer-specific PAFs by the corresponding cancer incidence estimates in 2015. The total proportion of cancer attributable to insufficient physical activity was calculated by summing up the number of attributable incident cases and dividing them by the total number of cancer cases (excluding non-melanoma skin cancers).