The present study is an unmatched hospital-based case-control study conducted at TMH in Mumbai, India. Patients were interviewed prior to diagnosis thus minimizing the interviewer's bias. However, the limitations of the study are the biases that are known in a hospital-based case-control studies. All prostate cancer cases registered during the year 1999-2001 could not be interviewed due to various reasons. The social investigators collected information in a predesigned well-structured questionnaire. The questionnaire included information on demographic characteristics, lifestyle habits, dietary habits, history of diabetes, hypertension, BMI, vasectomy, number of children, etc. Since very few case- control studies reported so far from India, the present study attempts to study the association of the various factors and prostate cancer risk.
Age emerged as the strongest determinant factor for prostate cancer in our study as well, which has also been recently shown in an Iran study.[10
] The difference in mean age between the cases (64 years) and controls (46 years) were distinct, essentially due to the fact that prostate cancer is known to be an elderly age disease, while those diagnosed as ‘free of cancer’ had some other ailments not linked to prostate, and also the patients were interviewed at the out-patient department. The authors agree that this is one of the drawbacks of the study, but the OR for risk factors has been adjusted for in the analysis.
Chewing of tobacco is common in India. Chewing includes chewing betel leaf with or without tobacco, pan masala or gutka. The present study showed no significant increase in risk for chewers, although tobacco chewing was more common. Although, no enhanced risk was observed for cigarette smokers in a population-based study conducted in Utah, USA;[11
] there are other studies which have reported the contrary viz. no increased risk for current smoker but increased risk for pack years of smoking.[12
] However, in the present study no excess risk was observed for smokers, in general, for prostate cancer. Tobacco did not emerge as a risk factor, and also due to the fact that the data on duration of tobacco use was incomplete, pack years of smoking or chewing was not considered in the analysis.
Information on alcohol drinking is difficult, but not impossible, to obtain in Indian situations because of the social stigma attached with this habit. The present study did not show any enhanced risk for alcohol drinkers and is in agreement with that reported earlier.[11
India being a country with varied religious groups, the dietary habits also vary across the religious groups. It is well known that diet has an important role to play in cancer risk. Despite the associations with meat eating, existing studies suggest that vegetarians do not have reduced risk of breast, bowel or prostate cancer and the present study too did not show any excess risk for meat eaters.[13
] Although an earlier study indicated a reduced risk for fish eaters, our study did not show any significant reduction in risk for prostate cancer.[14
] Tea and coffee drinking did not show any significant risk for prostate cancer in our study.[12
Studies in literature showed positive association of family history of cancer and prostate cancer risk; however, our study did not show any enhanced risk, even after adjustment for dietary and other risk factors.[4
Lower risk of prostate cancer among diabetics has been suggested by many, but not all studies. The possible reason for this inconsistency could be due to the fact that studies have not accounted for ‘time since diagnosis’ of diabetes mellitus, treatment duration or have not examined confounding factors such as diet. A Health Professionals Follow-Up Study from 1986 and 1994, in which 1,369 new cases of non-stage A1 prostate cancer were documented in 47,781 men was reported.[5
] Prostate cancer was not reduced in the first 5 years after diagnosis (RR = 1.24, CI = 0.87-1.77). In the present study, although patients with a history of diabetes had an elevated risk (OR = 2.5), it was not statistically significant; this could be attributed to the fact that the ‘time since diagnosis’ and also the duration of treatment taken for diabetes was not recorded. Information on history of diabetes was a part of the questionnaire and was based on interview and hospital records; however not all subjects underwent a gylcosylated hemoglobin level test. We know that there is an increase in the incidence of diabetes in India, but unless a study is carried out in detail whether the rise in prostate cancer cases is due to the increase in diabetes incidence, it cannot be said in affirmative; probably the time of diagnosis of diabetes, duration of treatment and dosage details would give an answer in this direction.
The findings on the association of hypertension and prostate cancer have not been consistent. However, the present study showed an 2.6-fold increased risk for prostate cancer for those with a history of hypertension and is in agreement with one of the earlier studies,[15
] whereas an other study did not find any association with prostate cancer.[16
It is known that obesity and physical activity can modulate the endocrine system. Cerhan et al
. (1997) demonstrated that greater BMI (wt/ht2
) (RR = 1.7 for BMI > 27.8 kg/m2
compared with BMI < 23.6; P
trend = 0.1) was a risk factor for prostate cancer. The present study showed that those who had a BMI greater than 24.9 (obese) had a two-fold enhanced risk for prostate cancer compared to those with BMI less than 25, which is in agreement with the findings reported in other studies.[7
] A Finnish study reported that middle-aged men with the metabolic syndrome were more likely to develop prostate cancer in this prospective population-based study.[17
] The association between metabolic syndrome and risk of prostate cancer was stronger among overweight and obese men with a BMI ≥ 27 kg/m2
(adjusted relative risk, 3.0; 95% CI, 1.2-7.3) than in lighter men (relative risk, 1.8; 95% CI, 0.7-4.7).
Those who had undergone vasectomy showed a two-fold non-significant risk for prostate cancer, which is in concurrence with an earlier study reported from India.[9
] As per the guidelines stated, men who wish to be screened for prostate cancer should have both a PSA test and a DRE.[18
] Similarly there was no association between the number of children and prostate cancer risk in the present study.
The present study demonstrates age, hypertension and BMI as important determinants for prostate cancer risk. Understanding the mechanisms underlying these findings may provide biological insights into prostate carcinogenesis. BMI is directly related to the diet and physical activity. It is possible that those who are obese (BMI greater than 24.9) are eating high-fat diet and are probably less active. A detailed study addressing these factors may provide the right lead in understanding the disease process. Additional information on physical activity will provide inputs for preventing prostate cancer. The authors agree that the number of subjects are less, which is a limitation of the study; nonetheless, this can serve as a platform to launch a larger study for study the aspects in detail, since there are no case-control study on prostate cancer from India reporting on these aspects.