Prevalence and factors associated with sexual dysfunction among middle-aged women in a multi-ethnic country: a cross sectional study in Malaysia by Tey, Yin Yee, Ching, Siew Mooi, Maharajan, Mari Kannan, Lee, Kai Wei, Chow, Zhen Yee, Chua, Pei Wen, Tan, Chin Xuan, Lim, Shi Nie, Tan, Chun Han, Thew, Hui Zhu, Ramachandran, Vasudevan, Hoo, Fan Kee