请根据博士论文的格式完善下面这段话的逻辑：综上所述现有关于NDVI与PM25暴露对老年人超重肥胖发生的研究存在以下几点不足：1环境物暴露与老年人超重肥胖的相关研究较少大部分国内外流行病学研究主要关注大气污染与儿童肥胖的关系或者与其青少年时期肥胖的关系或大气污染与普通成年人群的肥胖关系；2国外有关环境物暴露与老年人超重肥胖关系的前瞻性队列研究十分缺乏国内相关的一项队列研究也只是调查了45岁及以上人群

Based on the above, there are several limitations in the existing studies on the association between NDVI and PM2.5 exposure and the occurrence of overweight and obesity in the elderly. First, there is a lack of research on the relationship between environmental exposure and overweight and obesity in the elderly population. Most epidemiological studies in China and abroad have mainly focused on the relationship between air pollution and childhood obesity, or between air pollution and obesity in young adults and middle-aged adults. Second, there is a lack of prospective cohort studies on the relationship between environmental exposure and overweight and obesity in the elderly population, especially in individuals aged 65 years and above. The only relevant cohort study conducted in China only investigated individuals aged 45 years and above. Third, the accuracy of green space measurement data in existing studies is inconsistent. Some studies used exposure data at the district or county level, which cannot accurately reflect the individual exposure situation. Additionally, different measurement methods and data sources for green space exposure may lead to incomparable results. Fourth, existing studies failed to collect comprehensive information on potential confounding factors, such as smoking, drinking, exercise, diet, and health status, as well as the elderly individual's activity level, which may affect the occurrence of overweight and obesity, leading to potential bias and affecting the credibility of the results. Finally, most of the existing studies are cross-sectional or have a short follow-up time, unable to observe the long-term impact of environmental exposure on outcomes or the occurrence of outcomes. Additionally, the study design did not consider changes in the individual's address or changes in environmental exposure in the living environment, which may affect the results.