Joint associations of smoking and television viewing time on cancer and cardiovascular disease mortality

Abstract

Excessive sitting time and smoking are pro-inflammatory lifestyle factors that are associated with both cancer and cardiovascular disease (CVD) mortality. However, their joint associations have not been investigated. We examined the associations of television (TV) viewing time with cancer and CVD mortality, according to smoking status, among 7,498 non-smokers (34% ex-smokers) and 1,409 current-smokers in the Australian Diabetes, Obesity and Lifestyle Study. During 117,506 person-years (median 13.6 years) of follow-up, there were 346 cancer and 209 CVD-related deaths. Including an interaction between TV time and smoking status in the model significantly improved the goodness of fit for cancer (p = 0.01) but not CVD mortality (p = 0.053). In the multivariate-adjusted model, every additional hr/d of TV time was associated with increased risk of cancer-related (HR 1.23; 95% CI 1.08-1.40), but not CVD-related mortality (HR 1.16; 95% CI 0.97-1.38) in current-smokers. Elevated multivariate-adjusted cancer mortality HRs were observed for current-smokers watching 2 to <4 hr/d (HR 1.45; 95% CI 0.78-2.71) and ≥4 hr/d (HR 2.26; 95% CI 1.10-4.64), compared to those watching <2 hr/d. Current-smokers watching 2 to <4 hr/d (HR 1.07; 95% CI 0.45-2.53) and ≥4 hr/d (HR 1.92; 95% CI 0.76-4.84) did not have a significantly higher risk of CVD mortality, compared to <2 hr/d. No associations were observed for non-smokers. These findings show an association of TV, a common sedentary behavior, with cancer mortality in current-smokers. The association with CVD mortality was less clear. Further exploration in larger data sets is warranted. Limiting TV viewing time may be of benefit in reducing cancer mortality risk in current-smokers.

Sedentary Behavior and Health: Update from the 2018 Physical Activity Guidelines Advisory Committee

“…All studies used prospective cohort designs, with follow-up periods ranging from 2.3 to 19.4 years. The sedentary exposures varied across studies: five studies used self-reported sitting time (17)(18)(19)(20)(21), seven studies used self-reported TV viewing time (17,18,(22)(23)(24)(25)(26), and five studies used accelerometer-derived estimates of sedentary time (27)(28)(29)(30)(31). All studies included an estimate of duration of sedentary behavior (sedentary time) as an exposure, while three studies also included a marker of bouts or breaks in sedentary time as an exposure (27)(28)(29).…”

Differing Context-Specific Sedentary Behaviors in Australian Adults with Higher and Lower Diabetes Risk

“…Extensive evidence suggests increased TV viewing time is associated with poorer cardiometabolic health (6,(30)(31)(32)(33) and increased risk of CVD events and mortality (34)(35)(36). In comparison to other contexts of sedentary behavior, TV viewing can often occur concurrently with other detrimental health behaviors such as; poorer dietary patterns (37,38); sitting for longer, uninterrupted periods of time; and often occurs in the evening following a large meal (39).…”

“…Those with undiagnosed dysglycemia spent less time sitting while using a computer for leisure than those with normal glucose metabolism (2% in workers, 29% in non-workers). A potential strategy for reducing time spent in what may be deemed, more "metabolically harmful" sedentary behaviors, for example TV viewing (6,32,34,37,(44)(45)(46), aside from promoting movement, could be the reallocation of time from non-active to active sedentary behaviors. A recent study found non-active sedentary behaviors (e.g.…”

Reply to: Joint associations of smoking and television viewing time on cancer and cardiovascular disease mortality—Methodological issues

“…Pakzad and Safiri for their interest in our recent findings showing a joint association of smoking and television viewing time on cancer mortality. 1 Their comments appropriately point to the limitations of analyzing cancer mortality as a combined outcome, as the strength and direction of the associations between television viewing time and cancer have been shown to vary between different cancer types. 2 Consistent with that perspective, we acknowledge that combining all cancer outcomes for our analysis is not ideal.…”