This seems like a cosmic joke, but a new study shows this to be true. In fact, mothers would be better off taking care of themselves than to have a daughter-in-law look after them. You may be thinking, "Of course, they can't breathe with a pillow over their face."
In all seriousness, Japanese researchers conducted a four-year study where the scientists tracked nearly 200 elderly Japanese men and women. The results showed that a woman cared for by her daughter-in-law (while living with her son) was twice as likely to have died as one who lived with her own daughter. Researchers believe this is caused by the classic friction of mother and daughter-in-law relationships, where the stress finally takes its toll on the elder. As mentioned above, the mother-in-law would be better off living alone. What's not mentioned is what the relationship status was between the mother and daughter-in-law. If it is good, will that change the stats? This study (and the researchers conclusion) seems to assume that the relationship is bad. Read more here.