给出一段英文文本，将该文本按照其逻辑结构划分成相应的段落并提取每个段落的主题。
下面是一段英文文本。
According to a new study, people who sleep less than six hours a night may be more likely to develop cardiovascular disease than those who sleep seven to eight hours. The study followed approximately 4,000 adults over a 10-year period and found that those who slept less than six hours were 27% more likely to develop cardiovascular disease. The researchers suggest that lack of sleep may have a negative impact on the circulatory system, which could increase the risk of developing conditions such as heart attack or stroke. They also recommend that adults aim for seven to eight hours of sleep each night.
该文本可以按照逻辑结构划分成两个段落，每个段落的主题如下：

段落1：研究发现，睡眠不足的人比睡眠七到八小时的人更容易患心血管疾病。在接近10年的跟踪调查中，研究人员发现，睡眠不足6小时的人患心血管疾病的可能性比睡眠七到八小时的人高出27%。

段落2：研究人员建议成年人每晚应该睡七到八个小时，并指出睡眠不足可能会对循环系统产生负面影响，从而增加患心脏病或中风等疾病的风险。