To investigate the risk factor for the development of chronic kidney disease (CKD) is an important issue. However, there are some limitations in your study.

Major

1. In your study, participants answered questionnaires and donated blood samples at the baseline (2008) and 5 years after the baseline (2013). Your study subjects (i.e., target of data analysis) were 252 males who provided information from 2008 to 2013. Among them, cases were 23 participants developed CKD during the follow-up period while other 229 participants were controls. CKD patients answered lifestyle after the development of CKD in 2013. Therefore, it is unclear whether they changed their lifestyles because they became CKD patients or not. So, you cannot tell to investigate risk factor for the development of CKD in this study design. If you want to find risk factors for the development of CKD using the nested case-control study, you had better use the annual health check-up data just before the development of CKD for CKD patients. I think you can get these data.
2. Each factor of metabolic syndrome increases the risk of CKD (Reference: Japanese Society of Nephrology. Obesity, CKD and metabolic syndrome. In: Evidence-based guideline for CKD 2013. Tokyo Igakusha, 2013, pp157-158. in Japanese). Therefore, you had better show us the prevalence of high systolic blood pressure (130mmHg or higher), high diastolic blood pressure (85mmHg or higher), elevated triglyceride (150mg/dl or greater), low HDL cholesterol (less than 40mg/dl), high fasting blood sugar (100mg/dl or greater), and high HbA1c (5.6% or higher) in the baseline data. Please let us know whether these metabolic syndrome factors influence the risk of the development of CKD or not. If so, you had better adjust these factors when you evaluate the effect of lifestyle factors on the development of CKD.

Minor 1. Proteinuria as well as microalbuminuria is a risk factor for the progression of CKD. Please show us the rate of urinary proteinuria (±). Was proteinuria (±) associated with CKD in your study subjects? Was there any subject who had hematuria? 2. Deteriorated GFR causes hyper-filtration of glomerulus, which may progress glomerular-sclerosis. Compared with control subjects, did CKD subjects showed a greater rates of G2 at base-line in your study?
3. Please show us what is unhealthy lifestyles For examples. Frequent habitual moderate exercise (30min +/session and 2times +/week) Avoiding bedtime snacking (less than 3 times/week)