Background
We aimed to determine risk factors for incident CKD in a large population-based cohort.

Methods
This prospective opt-in population-based cohort study is based on the 45 and Up Study, where New South Wales residents aged ≥45 years were randomly sampled from the Services Australia enrolment database and agreed to complete the 45 and Up Study baseline questionnaire and have their responses linked to their health data in routinely-collected databases. The primary outcome was the development of incident CKD, defined as eGFR<60ml/min/1.73m2. CKD incidence was calculated using Poisson regression. Risk factors for incident CKD were assessed using Cox regression in multivariable models.

Results
In 39,574 participants who did not have CKD at enrolment, independent factors associated with developing CKD included: older age, regional residence (HR 1.38 [1.27-1.50] for outer regional versus major city), smoking (1.13 [1.00-1.27] for current smoker versus non-smoker), obesity (1.25 [1.16-1.35] for obese versus normal body mass index), diabetes mellitus (1.41 [1.33-1.50]), hypertension (1.53 [1.44-1.62]), coronary heart disease (1.13 [1.07-1.20]), depression/anxiety (1.16 [1.09-1.24]), and cancer (1.29 [1.20-1.39]). Migrants were less likely to develop CKD compared with people born in Australia (0.88 [0.83-0.94]). Gender, partner status and socioeconomic factors were not independently associated with developing CKD.

Conclusions
This large population-based study found multiple modifiable and non-modifiable factors were independently associated with developing CKD. In the Australian setting, the risk of CKD was higher with regional residence. Differences according to socioeconomic status were predominantly explained by age, comorbidities and harmful health-related behaviours

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