Early menopause in smokers is linked to a higher risk of bladder cancer, new research shows.
The study*, which looked at health outcomes of more than 220,000 US nurses, is presented at the European Association of Urology congress in Barcelona.
The US and European scientists studied the medical history of nurses who had enrolled in the Nurses' Health Study I and II, which have been following the health outcomes of more than 220,000 US nurses since 1976. They found that women who went into menopause before the age of 45 were 45% more likely to have bladder cancer than those who had later menopause (after 50). If these women had smoked, the risk of bladder cancer was 53% greater than women who had later menopause.
Lead researcher Dr Mohammad Abufaraj (now working at the University of Vienna) commented: "We found that smoking women who experienced menopause before they were 45 years old had a greater risk of bladder cancer. Smoking remains the most important risk factor for bladder cancer. Our data also revealed that it is unlikely that female factors such as age when periods begin, number of pregnancies, oral contraceptive use or the use of hormone replacement therapy are associated with bladder cancer risk. Smoking is associated with earlier age at menopause thereby further increasing the risk of developing bladder cancer.”
The number of cases, and the number of people who die from bladder cancer, varies significantly from country to country. In general, around three times more men than women get bladder cancer, but the mortality rate in women is around 40% higher. There are many explanations for these differences including delay in diagnosis, genetic/epigenetic factors and hormonal factors.
Dr Abufaraj added: "This study indicates that earlier age at menopause seems to increase the risk of bladder cancer. Our primary interpretation is that a factor like smoking, which is known to correlate with earlier age at menopause, remains of grave concern as the main cause of in bladder cancer. It reinforces the warning that smoking really is harmful in ways that we might not have easily imagined.”
Previous research from the same research team has shown that smoking has a dose-response relationship with prognosis in both early and advanced bladder cancer. However, 10 years after stopping smoking, this risk had returned to the same level as that of non-smokers.
The 34th European Association of Urology conference takes place in Barcelona from March 15-19.
*Abufaraj M, Shariat S, Moschini M, et al. The impact of hormones and reproductive factors on the risk of bladder cancer in women: Results from nurses’ health study and nurses’ health study II. Presented at the European Association of Urology congress in Barcelona, March 15-19 2019.