Lam Man-hing, a 70-year-old Hongkonger who has survived three bouts with cancer, has vowed to spend the rest of his life caring for his wife, Tang Siu-man, who was diagnosed with Alzheimer’s disease eight years ago. Lam said he can bear the idea of his wife forgetting about him and all the members of their family, as long as Siu-man feels comfortable and willing to follow him.