The results showed that during the past four decades, the overall ASIR (per 100,000 person-years) of oesophageal cancer was 10.51 in Kuwait. This estimate is comparable with those recently reported in Eastern Asia (11.1), but is nearly twice as much of the estimates reported from South-Central Asia (4.8), sub-Saharan Africa (4.2) and other world regions [13]. This global variation in ASIRs of oesophageal cancer may be owing to varying lifestyle and dietary patterns. The two established risk factors for oesophageal cancer are excessive alcohol consumption and tobacco smoking. Parenthetically Kuwait ranks very high worldwide for tobacco consumption prevalence in men (33.7%) and women (4.7%) [14], with parallel high ASIRs of oesophageal cancer, which indeed fulfils the Bradford Hill’s criterion of ‘coherence’ for causal link between tobacco smoking and oesophageal cancer.
The multivariable ZINB model showed that increasing age was associated with the increasing trend in the oesophageal cancer risk, which reflects a cumulative effect of carcinogenic exposures. The modification of known risk factors for oesophageal cancer may lessen the risk later in the life. Moreover, males had marginally increased oesophageal cancer risk than females, which outwardly related to sex hormones and lifestyle factors including smoking and dietary factors [7, 8]. Additionally, over the past four decades, oesophageal cancer risk consistently declined in Kuwait. Towards the end of twentieth century oesophageal cancer risk had been increasing in both sexes in USA, Europe, Japan and China [15, 16], which in recent decades showed a declining trend in these regions as well [15]. Similarly, downward trends with varying magnitudes in oesophageal cancer incidence were recorded in Hong Kong [17], and China [18]. These declining trends in oesophageal cancer incidence ostensibly is due to varying distributions of contributory risk factors across different populations [15, 19]. For example, in Kuwait, tobacco smoking by any mode including cigarettes, cigars and pipes showed a consistently declining trend with varying rates (5-6%) from 2000 to 2018 and stabilized thereafter, which seems to concur with the decreasing trend of oesophageal cancer in Kuwait [20].
In conclusion, an overall high oesophageal carcinoma ASIR was recorded. ASIRs consistently declined from1980 to 2019. Older adults (≥ 60 years) and Kuwaiti nationals were high-risk groups for oesophageal cancer. An educational intervention based on the known risk factors may alleviate oesophageal carcinoma risk in this and similar settings. Future studies may contemplate to evaluate the effect of such an intervention.
