Comparison of cancer incidence in Australian farm residents 45 years and over, compared to rural non-farm and urban residents - a data linkage study

Julie Depczynski,Bruce Armstrong,Timothy Dobbins,Tony Lower

doi:10.1186/s12885-017-3912-2

Julie Depczynski, Bruce Armstrong + Show 2 more

Open Access

https://doi.org/10.1186/s12885-017-3912-2

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Abstract

BackgroundIt is not known if the incidence of common cancers in Australian farm residents is different to rural non-farm or urban residents.MethodsData from farm, rural non-farm and urban participants of the 45 and Up Study cohort in New South Wales, Australia, were linked with state cancer registry data for the years 2006–2009. Directly standardised rate ratios for cancer incidence were compared for all-cancer, prostate, breast, colorectal cancer, melanoma and non-Hodgkin Lymphoma (NHL). Proportional hazards regression was used to generate incidence hazard ratios for each cancer type adjusted for relevant confounders.ResultsFarm women had a significantly lower all-cancer hazard ratio than rural non-farm women (1.14, 1.01–1.29). However, the lower all-cancer risk observed in farm men, was not significant when compared to rural non-farm and urban counterparts. The all-cancer adjusted hazard ratio for combined rural non-farm and urban groups compared to farm referents, was significant for men (1.08,1.01–1.17) and women (1.13, 1.04–1.23). Confidence intervals did not exclude unity for differences in risk for prostate, breast, colorectal or lung cancers, NHL or melanoma. Whilst non-significant, farm residents had considerably lower risk of lung cancer than other residents after controlling for smoking and other factors.ConclusionsAll-cancer risk was significantly lower in farm residents compared to combined rural non-farm and urban groups. Farm women had a significantly lower all-cancer adjusted hazard ratio than rural non-farm women. These differences appeared to be mainly due to lower lung cancer incidence in farm residents.

Highlights

It is not known if the incidence of common cancers in Australian farm residents is different to rural non-farm or urban residents
The current study aims to examine whether associations between cancer incidence and being a farmer or farm resident noted in other studies, are apparent in a large Australian cohort
Standardised rate ratios for cancer incidence and adjusted hazard ratios by gender for each cancer are shown in Tables 1 and 2

Summary

Introduction

It is not known if the incidence of common cancers in Australian farm residents is different to rural non-farm or urban residents. The most commonly diagnosed cancers in Australia include prostate, colorectal, breast, lung, melanoma and lymphoma [3]. The distribution of these cancers varies across rural and urban areas. Most recent studies have reported reduced cancer incidence in farmers for all-cancer lung, breast and colorectal cancers [7,8,9,10,11,12,13], Possible reasons suggested include a healthy worker effect; greater levels of physical activity; differences in smoking rates; and the protective effects of farm endotoxin exposure [14]. Pesticides and certain animal exposures are amongst the reasons suggested for the elevated risk of prostate and lymphohaematopoetic cancers [14, 27], findings vary by location, study design and degree of control for confounders which can affect comparability and the strength of conclusions drawn [27, 28]

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